Featured Post

Is the new professionalism and ACP's new ethics really just about following guidelines?

The Charter ( Medical Professionalism in the New Millennium.A Physician's Charter) did not deal with just the important relationship of ...

Tuesday, September 21, 2021

Anti Hubris thoughts for medical students-- "our ignorance is boundless"


Sixteen years ago I posted an entry on this blog in which I suggested an anti-hubris courses ( or at least a few lectures) for medical students.

I did not have all the content of this course prepared  (and still have not) but I do have the sense of it and some great quotes which I will sprinkle below.

 The following is a lightly re-edited version of that entry.
 
Most of the  sense of it is from the writings of Norton Hadler and much of it can be found in his article on various European backache compensation systems (JOM,vol 31, pg 823, 1989). In it he speaks of clinical truth which he distinguishes from scientific truth-although scientific truth must be utilized in obtaining clinical truth-and from legal "truth"-which is incidental to settling the dispute at hand. Clinical truth is or is derived from a contract between a physician and a patient and is based on trust.He said it better than I can and his article would be required reading in this "anti-hubris" course.

Our approaches are provisional and based on fragmentary information and when I think about the algorithms and paradigms that are in our tool boxes, Boris Pasternak's quote appears as an emphatic "yes..but", "What is laid down, ordered, factual, is never enough to embrace the whole truth:Life always spills over the rim of every cup". Karl Popper said " we know a great deal but our ignorance is sobering and boundless...all things are insecure and in a state of flux".


All of this does not mean that we can't pull out the latest guidelines from whomever on our smart phone and see if that does or does not apply to the case at hand.But the operative words there are "see if it applies to the case at hand." The experienced physician has one- at least one-advantage over the younger one, he has seen the 180 degree changes in a given algorithm or clinical guideline. Plaintiff attorneys are fond of saying to the expert witnesses ,"Doctor,were you wrong then or are you wrong now" in the situation where there is an apparent contradiction.

Medical students need to know-in regard to the "factual knowledge" imparted to them- that while that material may be the very best that the very best of minds can determine at this time that they need to stay tuned because all of that may change at any time and the physician will have to decide what to do for the patient even before the next authoritative pronouncement is prepared.In that decision she will have to call upon her knowledge,expertise and judgement and the patient's values and views and do her job the way physicians have for many years before guidelines were part of medical language and work with the patient for their particular clinical truth.

"Life is short,the art long and judgement fallacious." is a hard quote to beat.
 .

Wednesday, September 15, 2021

Still another variation of conduction system pacing -left posterior fascicular pacing

 The right ventricular apex was the preferred site for ventricular activation for pacemakers for several decades.After the realization that apical pacing was associated with an increased risk of heart failure and atrial fibrillation his bundle pacing was rediscovered.Although two cases series of his bundle paced patients were published  in the 1970 s it was not until over forty years later that his bundle  pacing finally began to become established and it was claimed by some electrophysiologists that the era of physiological pacing had  arrived. 

Although his bundle  pacing was considered to be physiologic,it was more technically daunting and typically required a higher ventricular capture voltage.There was also  some frequency of delayed lead displacement  and a shortened battery life paralleled the higher capture voltages.

In 2017 Huang et al described the next development in conduction system pacing-left bundle branch area pacing.  In this technique the sheath is advanced about 1.5 centimeter from the site of his signal recording towards the apex and deeply inserted into the ventricular septum.It is less technically demanding than is his bundle pacing  and requires a lower capture voltage and in some EP centers i has replaced His pacing as the go to conduction system pacing of choice.

 In 2020 Ponnusamy et al (1)described a case in which they were unable to obtain a satisfactory left bundle branch area lead placement and  then maneuvered the lead  2 cm lower and positioned the lead in the area of the left posterior fascicle. A similar case had been described by LJ Zen et al in 2019(2)

The 12 lead EKG with Left posterior fascicular pacing demonstrates a pattern of left anterior hemiblock. 


1) Ponnusany, SS et al. Left posterior fascicular pacing. J Innov Cardiac Rhythm Manage 2021 12 (5) 4493

2)Zeng, l, et al Permanent left posterior fascicular area pacing through the interventricular septum in a patient with infra-Hisian block, Heart rhythm Reports, 2019, Aug 5 (8) 411-413

Saturday, September 04, 2021

Long time endurance athletes long time outlook looks good less so for "power" sport advocates

 Dr Runacres (I am not making that up) et al published a meta-analysis of 165000 long time athletes and found , as have other studies, that endurance athletes have lower  cardiovascular mortality and all cause mortality but that does not hold true for long devotees  of power sports. See here 

Friday, September 03, 2021

September 2021- US in another surge in spite of excess vaccine and plenty of masks

 Here we are in another covid surge in the US even though there are no shortages of masks or vaccines.Neither is there a shortage of people who oppose the use of vaccines and masks nor is there a shortage of people seemingly ignorant of the seriousness of the Delta variant driven surge and stress placed on the health care system. 

Neither is there the  previous  official ignorance about the basic transmission mechanisms of Sars Cov2 spread. 

It was not until April/May 2021  that the CDC and WH0 finally abandoned  the primacy of the 100  year old dogmas put forth by Charles Chaplin which said that the basic mechanisms of respiratory disease spread were by droplets and fomites. 

By September  2021 it is well established that Sars Cov 2 can spread in pre symptomatic and asymptomatic people by the aerosol route and that measures directed at droplets and fomites will not suffice. Well fitted high grade masks ( eg.N95s) are needed as well  as mitigation efforts directed along the lines of ventilation, and air flow,  air filtration and air exchange  in indoor settings to complement a vaccination and testing program.

So we know more and should be better  prepared and yet in some parts of the country we are seeing high deaths and hospitalizations. We see parts of the country in which mask wearing is much less than it was in the 2020 surges.Parts of the country that had mask mandates in 2020 now have "anti mask mandates" that prohibit local authorities from imposing mask mandates. Anti mask and anti covid  19 vaccine advocacy flourish on social media and right leaning radio and tv. We know what to do to mitigate the spread of covid 19 but many are defying those measures and apparently many others seem indifferent.

Watching the Astros on TV play at home on in Dallas the optics are the same, virtually no one in the stands wear a mask. even though Covid is surging in Texas.

Whatever effect anti mitigation efforts may or may not be having on the magnitude of the spread  of the Delta variant, its  increased infectiousness has to be considered a primary cause of the latest surge.Delta is clearly more infectious and there is growing evidentiary support for the claim that it is more capable of causing serious disease than were earlier variations. At a time when a more contagious variant is surging we are also seeing surges in ignorance, indifference and political ambition all of which make the  magnitude and speed of spread  even worse. 

Thursday, September 02, 2021

Why the US Covid Delta surge may not burn out as quickly as it did in England.

 The rapid uptick and downtick of Delta observed in England has been thought by some to predict  a similar course for the US but the opening of schools may b ae wild card and the Delta surge may not end as quickly as it did in England.

Both Dr. Michael Osterholm and  Dr.Larry Brillant offer a more pessimistic prediction because of their concern that the opening of schools across the country will provide fertile ground for spread and also  offers a platform for virus mutation.

In numerous areas of the country students will not be masked and only a small percentage of high school and primary school kids will be vaccinated. In several states there  has been a concerted effort by the governors and sometimes that state legislatures to issue executive orders and pass legislation  the effect of which is to limit the use of masks and certain other virus mitigation measures in schools and to restrict the right of a private company to  use  " vaccine passports".  


Osterholm in, a recent interview said that a multi layered approach is necessary ..Ventilation is important ( i.e 5-6 air exchanges per hour),as are HEPA air filters and use of proper masks ( e,g, N95 or KN95). Testing students,staff and teachers  several  times a week and removal of positive cases. The importance of airborne transmission makes the popular plexiglass barrier not very effective and may be more for show than efficacy.

The CDC and the American Academy of Pediatricians recommended  masks for school kids.Governor Abbott and Governor Desantis have issued executive orders forbidding local school boards to issue mask mandates.

Another reason that the US might not echo the path taken in England may relate to the different sequencing of vaccination doses.England had a longer period between shot one and shot 2 which has been offered as an explanation for the greater time related decreased in vaccine efficacy in the US versus England and Canada who also opted for the longer time between the 2 doses of the mRNA vaccine.


Tuesday, August 24, 2021

CDC realizes the vaccinated can spread covid 19 delta variant-now what

 CDC has now seemingly realized that fully vaccinated people can harbor large amounts of the delta variant in their noses and are able to transmit the disease to others. This is a conclusion that could have been reached upon analysis of the Houston Wedding event in which 6 fully vaccinated attendees develop covid  although admittedly there are alternative  less likely explanations for the Houston wedding cases.

In May 2021  when CDC seemed to set people free from mask use the data it had indicated that the likelihood of spread  from the fully vaccinated was low enough to recommend that masks were no longer necessary for vaccinated people under many circumstances.

But by July 29 with access to new data CDC concluded  that fully vaccinated people could  actually spread the disease and that the data they relied on for that conclusion would soon be released. That data is now available Further the greater infectivity of the Delta virus prompted CDC to express a much greater concern.

It now seems that the following should be considered the  operational reality on the ground.

1. Fully Vaccinated people can develop and spread covid 19 delta variant.In the vast majority of cases the disease is either mild or asymptomatic.

2.Some very small  percentage of fully vaccinated people can develop serious and fatal covid 19

3.Delta variant infection results in significantly higher viral loads and infectivity and possibly 

more serious disease. (data from Canada ,Singapore and Scotland  show Odds Ratio for ICU admission range from 3.87 to 4.9 ) 

4.Large areas of the US have relatively low levels of full vaccination 

So practically what does all of this mean.

If you are vaccinated you still  may need to wear a mask.

Why?

Since fully vaccinated people can spread covid wearing a mask protects others. There are two sets of others, the vaccinated and the unvaccinated.  A vaccinated person can contract covid and bring it home to infect children and the elderly. 


If you are not vaccinated you need to wear a mask.Masks should be N95s and ideally covered by a blue procedure or surgical mask.After exposure the mask could  be stored in a container so that they can be used after a several days period of "decontamination "  Adding a face shield to the mask may add another layer of protection although strong supporting data to that point seems not to exist The double mask has not been recommended this time by the CDC but that was recommended for a surge from a Covid version that was less contagious and perhaps less lethal than the delta strain.. Now the CDC advises that the vaccinated should wear masks if they live in a area with a high test positivity rate and a low rate of vaccination.

5.At least some of the geographic  areas cited in item 4 have governors and/or legislators who resist or oppose the standard public health measures used to control epidemics of contagious respiratory disease specifically mask and vaccine mandates. Quantification of the harm that is causing awaits the scrutiny of epidemiologists.



Monday, August 23, 2021

Breakthrough Covid cases-how many vaccinated ? Unvaccinated ?

 In the pre Delta variant era the vaccines were thought to be the answer. The expectation and hope were that a vaccine could provide immunity, stop spread and push us all to the elusive herd immunity and life would return to the pre Pandemic norm.

And for while it  appeared that was the case.As cases numbers dipped lower and lower by the spring 2021 it appears that the worse was over at least in the US and by May  2021 the CDC believed it was time for the fully vaccinated to no longer wear masks with a few exceptions noted ( eg the immunocompromised, in health care setting etc)

But then the Delta variant spread rapidly mainly in the southern states whose vaccination numbers lagged behind. Data from Israel and the US now seemed to indicate that fully vaccinated (FV) people could not only contract Delta but they could spread it.A wedding outbreak in Houston seemed to indicate that fully vaccinated people could spread it to each other. We were learning that Delta was definitely more contagious and data from Canada and Scotland suggested it was also more virulent. 

So while the vaccine promises were not met in some regards it was believed and regularly quoted by the public health and vaccine experts that the vaccine really worked well in that serious disease -the type requiring ICU care,was quite rare. 

Even with or  perhaps because of the unpresented avalanche of covid data published it has been difficult to determine how common are breakthrough cases, how frequent are the serious cases and who does it mainly attack ( is it only a disease of the unvaccinated?) ?  

Data from Israel is instructive. Israel is like an experimental lab for the world.Israel has 78% of its citizens who are over age 12 years fully vaccinated. Most if not all of the citizens are members of one of the HMOs which collect individualized  data which seems to be quickly available for analysis.

Israel is in a Delta surge . A 78% vaccination level is not high enough to prevent Delta surges. 

As of data from August 15 2021 there are 514 patients in hospital. Of those 59% are fully vaccinated  and 87% are over age 60 years. See foot note 1

In Israel serious breakthrough Covid 19 due to delta variation is not rare.

Is serious breakthrough really rare in the US or do we just have not the data to know what is going on with Delta?  Eric Topol and Dr L Wen have been critical of CDC for our flying blind predicament.

Antibody levels have been shown to be decreased at 6 months for both Moderna and Pfizer. Antibody responses in the elderly have been shown to be lower  Does that explain the preponderance of older patients in the Israel ICUs. Increased infectiousness of Delta and decreased antibody levels in patients immunized 6 month or more ago are suspects in regard to delta breakthroughs.intensified by less public attention to masking and distancing.

The case is strong for older folks both vaccinated and unvaccinated to wear masks in congregate settings and the CDC has recommended that as they walked back their May proclamation of no masks for most of the vaccinated.It seeems as if the public heard and remembered the CDC May advice but not their retraction or so it seems based on my personal observation of how few people in Harris County Texas are wearing masks. 

Will the booster fix the covid surge? Well, already Israel has reported 37  breakthroughs  after the booster shot but also have reported strong neutralizing antibody response to a booster mRNA jab. 

 foot note1)

Jeffery Morris (1) offers a illuminating discussion of the Israeli data in which  he demonstrates that when  the overall aggregate data are used the vaccine efficacy is calculated to be lower than it is in either group when the population is stratified  into two groups by age which we are told is an example of Simpson's paradox. His argument is that the "real" VE for serious disease is not as suggested by computing a VE based on the aggregate  data. My take is that  yes  the loss of efficacy for severe disease is not as great as a simple data display would suggest but my main point ,ie the breakthrough cases are not rare, seems solid .

1)Morris,J.  Israeli Data- how can efficacy versus severe disease be strong ... www.covid.data science


Wednesday, August 11, 2021

Will the current non-plan of "Maybe delta will have a rapid downturn " really work?

 As the delta wave continues to surge steeply upward some optimistic public experts project that US will see the rapid downturn in attack rate noted in England It is nice to think so but...

The US differs from England in at least the following ways:

1.England gave their second dose later than in the US perhaps giving the vaccinated a higher antibody level when Delta landed onshore  

2.  Some or many Brits continued to wear masks even after the controls were lifted.Arguably to a higher degree than in US.

3) England did not have powerful  elected regional leaders actively opposing mask wearing as governors of several  states in the US are now doing.

Dr Eric Topol is critical of the CDC current performance. First CDC was premature in their announcement in May that masks were no longer necesary for the fully vaccinated. The next mistake, in his view and in that of Dr. Leana Wen was to discontinued surveillance of breakthrough cases that were not serious enough to require hospitalization. Further according to Topol they should be doing genomic analysis on breakthrough cases and studying their antibody levels and noting  when and what kind of vaccine they received.  Basically Topol is saying we are flying blind  regarding the delta surge.Additionally CDC is admixing breakthrough case numbers from the pre delta times frame with those of the post delta period giving a falsely optimistic estimate of the fatality rate which in turn tends to negate the impact of their "wear mask again" advice.

From my admittedly limited personal experience in Texas  people just do not seem to be taking the surge seriously. This should not be surprising   One elderly  family friend eats out serval times a week and is now to attend a mini high school reunion Another elderly couple is planning a family union. A large local church is still living by the May CDC recommendations ignoring the most recent CDC advice as well as a recommendations by the county commissioner.Looking over the crowds at the  Astros game, only a few masks are seen. Local  authorities  have been forbidden by executive order to issue mask mandates even though delta is clearly more contagious and arguably more virulent  than the version of covid dominant in earlier surges.




Sunday, August 01, 2021

Why does the Pfizer vaccine seem to work significantly less well In Israel

 Data (1) are available regarding effectiveness of   the Pfizer 2 dose mRNA vaccine in Israel,Canada and England/Scotland.

As regards the vaccine effectiveness  (VE) against the Delta variant  there is a wide difference  in the  values for VE for symptomatic disease .For Canada and England/Scotland there are  values of 87 % and 89% versus 64% for Israel.

Both Canada and England/Scotland administered the vaccine not according to the time frame used in the clinical trails for  Pfizer. Due as in part to a  shortage of vaccine in Canada a decision was made to give the second short 4 months after the first .

 In England/Scotland  a similar decision was made to postpone the second shot to maximize the number of  people who received the first shot as the alpha variant was surging at that time.This was done with the realization that they using a dosing schedule different from that used in the clinical trials which is inconsistent with standard method of applying clinical trial results to clinical practice. The British decision was controversial. Some suggested that a partially immune population ( i.e many folks with only a single jab) along with a surge in cases was a set up for a  perfect storm of super surging.

  In Israel, which was not facing a vaccine shortage,the decision was made to give the vaccine according to the time schedule that was carried out in the clinical trials.Also in the US The mRNA vaccines were given according to the time schedule used in the trials.So, will the data for the US show a pattern more like Israel or\more like Canada?

One explanation for the international disparity in vaccine effectiveness  is that the longer delay between doses of the mRNA vaccine results in a more robust  protective response. Could this be another example of "sometimes it is better to be lucky than good"? Perhaps confounding the comparison is the fact that the degree to which Delta was prevalent in the populations varied, i.e.  possibly more Delta at the time of the Israel data compilation. 


1) I based this blog  in part on a slide presented by CDC on or about July 30, 2021 which I believe in turn was derived from several sources including Sheikh,  a. SARs-COV 2-Delta in Scotland.Lancet vol 397 p 2461,June 26 2021 

and an article by B Lopez et al Effectiveness of Covid 19 vaccines against the B.1.617.2 (Delta) variant NEJM July 21, 2021 



Saturday, July 24, 2021

Is the US into the 4th ( or 5th) surge of Covid

 Is the US already into the 4th surge of covid pandemic?

Cases and hospitalizations and ICU admission are definitely trending upwards.

Physicians in Alabama,Mississpii,Arkansas and Louisiana are pleading with the public to get vaccinated as they see cases in their hospitals surge and young people are being intubated.

In California, mask mandates are back while in other states governors deny the need and at least one governor (Colorado) said no restriction or mask mandates are necessary until  it is clear that hospitals are being over whelmed. 

It is time already for masks to come back .The CDC mask lifting in May was premature and widely misunderstood and IMO has been  in part, perhaps in large part,responsible for the rise in cases caused by the Delta variant.

The public experts interviewed on TV appropriately emphasize the importance of the unvaccinated getting the jab but if miraculously everyone rushing to the largely empty vaccination sites today it would be over a month before immunity would be obtained. Meanwhile the vaccinated as well as the unvaccinated need to wear mask indoors and in congregate settings. 

The Israeli data and British data differ significantly regarding the effectiveness of the Pfizer vaccine as regards preventing infection (33 %- 88 %) but agree as to a 90 Plus %value for prevention of death or serious illness. But in the worse case scenario many vaccinated persons can contract disease and likely spread the disease making in the short and intermediate term masks and social distancing a high priority. Fully vaccinated parents can contract the disease and spread it to their under 12 year old children who are currently not eligible for vaccination.

Unfortunately until the CDC makes important revisions in its mask recommendations businesses are not as likely to reinstitute mask mandates and masking is essential  until a sea change occurs in the large segment of the population who continues to be vaccine "hesitant". 

Dr. Scott Gottlieb tweeted "CDC has consistently been through,meticulous and late" and that they are not suited to provided quick solutions to emergent problems. He also said CDC's decision to tell the vaccinated that they could unmask was based in part on the demonstrated low risk of a fully vaccinated person to  contract or spread  the earlier variants of covid. That advice clearly does not apply to the Delta variant. 

 


Friday, July 23, 2021

Heavy viral loads with Delta results in greater infectivity setting up 4th US surge

 The 4th covid  wave is already in the US. It is  fueled by the much greater infectivity (1) of the Delta variant  arriving at a time of nationwide reduction in masking and social distancing in part driven by what a increasing number of public  health officials  believe to be a premature and widely misunderstood lifting of the mask mandate\by the CDC.

Some virologists are estimating the R naught of Delta variant to be as high as five. Anecdotal report from Australia indicates that viral transmission occurred with simply passing an infected person in a mall.That seemed to me unlikely until I read of the Chinese study demonstrating a viral load in Delta infected persons greater  than one thousand times that of the original Wuhan strain. Their report found that high viral loads persisted up to 4 days in asymptomatic patients. Asymptomatic spread from  persons with high viral load is pretty  good if not perfect storm for spread in a population who just recently were officially relieved of need to mask or distance.

The report of  transmission of the Delta variant among fully vaccinated people at an outdoor wedding event  in Houston seems to strongly indicate that transmission can happen in fully vaccinated people which should mean that not just the unvaccinated should wear masks in public but so should the vaccinated.

The vaccinated should wear masks in public for two reasons; 1) they can spread the disease to the unvaccinated which includes children who are too young to be currently eligible for vaccine  and of course the elderly and immunocompromised 2)there are "break through" cases  i.e cases in the vaccinated These are usually described as "mild" but some are not and there have been deaths largely in the elderly. 

Israel quickly reacted to increased Delta cases by reinstituting  a mask mandate  as did Los Angles County in California. The medium term answer is more vaccination but the short term answer is masking and social distancing .Already governors in Colorado,Florida  and Texas have said they will not mandate masking for the public and will not "allow"  mask mandates for kids returning to school although that is the recommendation of the American Academy of Pediatrics.

 

With this wave it looks like there will be fewer deaths in the elderly ( mainly because of the higher vaccination rate in the old folks) but reports from Alabama, Arkansas and Louisiana hospitals indicate that ICU admissions and some  deaths are occurring in the younger group. Whether  that indicates a greater lethality  from Delta is not determined at this time.

 

 





1)Viral infection and transmission in a large well-traced outbreak caused by the Delta SARS-CoV-2 variant - SARS-CoV-2 coronavirus / nCoV-2019 Genomic Epidemiology - Virological

Tuesday, July 20, 2021

More covid lessons from Israel and Houston Wedding

 Recent data from Israel. Of 61 patients hospitalized because of covid , 24 were unvaccinated  and 37 were fully vaccinated, Of the 37- 36 were over age 60 and one was in their fifties.

Clearly being fully vaccinated does not provide 100% protection against being seriously ill. Older people are not immune to developing serious covid 19 illness even after 2 shots of the mRNA vaccines.

Earlier the Israeli Health Ministry released the following summary without the detailed data on which the conclusions were made:

 The effectiveness of the Pfizer vaccine for prevention of disease was said to be 64% and the effectiveness as regards prevention of serious disease was 93% . Both values were in in the 90s from the randomized clinical trials for Pfizer.  

Why are they so different. Perhaps the antibody levels induced by the vaccine have decreased over time to a point at which the disease protection ability has also decreased. The other likely explanation is increasing number of cases due to the Delta variant.Both could be operative.

From the Houston wedding case report we have to conclude that serious covid 19 disease can occur with spread of the virus from vaccinated person(s) to another vaccinated person. 

An important question is:

1)Can a fully vaccinated person transmit the virus to another person? The Houston wedding  story makes it apparent that the answer is yes. While we do not know with a solid level of certainty the chain(s) of transmission in that spreader event  it seems most likely that at least one fully vaccinated person gave it to at least one other fully vaccinated  person.For that conclusion to be valid we have to assume there were no unvaccinated individuals, perhaps a service  person or a valet parking attendant  who could have transmitted the virus to all six of the infected attendees. 

Those type epidemiologic details would be important because if the fully vaccinated can transit the disease to the fully vaccinated and of course to the unvaccinated than the CDC advice for the vaccinated to do whatever they were doing before the pandemic without masks needs to be revisited and revised particularly as the Delta variant spreads

Further if vaccinated persons can spread the virus and since we know there can be asymptomatic spread and we know that there is aerosol spread then vaccinated persons should not go mask less in congregate settings such as grocery stores and churches to mainly protect others as well as themselves.

What about protection of children too young to be eligible for vaccination? Vaccinated parents should wear masks in public to minimize the risk of bring a covid virus home to infect the child.The vaccinated parents are very unlikely to get seriously ill from the Delta variant but may be  able to transmit the virus to their unvaccinated child. 

Mask wearing became a political issue earlier on in 2020 and when the discussion turns to why do folks oppose mask reading one purposed reason is "libertarian thought".

There is nothing libertarian about the vaccinated tossing the masks away if there is asymptomatic spread even among the vaccinated. One does not have the right to put others at risk. The foundational libertarian principle is that of non aggression i.e. one does not have the right to initiate force against another, Libertarian thinking is sometimes blamed for mask aversion but if someone believes he can spread a potential fatal disease to others  and if he does not wear a mask that is not libertarian exercise of a right  but rather a hostile act. 

So what are the lessons from recent Israel data and the Houston wedding story.

1) If and when the Delta variant is increasing in a community ( particularly  in a community with low level of complete vaccination ) people who have been vaccinated should not believe themselves to immune to covid They can spread the disease and there are break through cases..The CDC proclamation was poorly understood  or taken to mean to be no mask at all under most all circumstances. More troublesome is the obvious fact that everyone who is mask less is not fully vaccinated. Less than 50% of residents of Harris county Texas,home of Houston, have been vaccinated but try and find more than one or two people with masks when a crowd shot is shown at a Astros home game.Further, one shot of either of the two mRNA vaccines does not protect against the Delta variant.

2)Vaccinated people can get seriously ill from Covid and  some will  die.

3)With the increasing spread of a many time more contagious everyone should wear a mask in congregate setting to as was true in the beginning of the pandemic to protect others and yourself.

 The CDC said that masks may still have to be worn when government regulation (Federal or state or local) so indicates. Unfortunately in some states the legislature and or the governor have decreed that business may not demand a "vaccine passport" and/or that public schools cannot mandate vaccination or masks regardless of what the level of risk may be.

As cases again begin to spike, CDC needs to revise its mask guidelines and when a virus is on the ascending limb of spread time is of the essence.


 



Sunday, July 18, 2021

Documented cases of Delta variants in fully vaccinated patients

 The setting was an outdoor wedding near Houston Texas for which only vaccinated persons were allowed to attend. Fully vaccinated and outdoors-and yet six cases with 2 hospitalized and one death. 

See here for the pre print .

Of particular interest in patient 1 who had received the Pfizer vaccine and had no comorbidities.He required hospitalization and was treated with Regeneron antibody with recovery.

Patients 0a and 0b traveled  to the wedding from India and tested negative before the flight.Patient 0a was hospitalized and died from covid19 complication one month after the event. Both of the visitors from India had received the Indian covid vaccine.

The planners of the wedding were careful-having the event outdoors and required the quests to all be fully vaccinated. The report does not mention whether masks were worn but according to CDC recommendation masks are not required for outdoor events for fully vaccinated people.

Eight fully vaccinated health care workers apparently contracted covid 19 at a swimming party.All were mildly ill with upper respiratory symptoms and self quarantined. See here for link.These cases were much milder than some of Houston wedding guests who contracted covid and also seemed linked to the Delta variant. 

Clearly fully vaccinated does not mean fully protected from the Delta variant.


Should the CDC's mask advice be fine tuned in view of the increasing number of Delta variant cases and its apparent increased infectiousness and possibly capability to evade the vaccine's protection.Another element in the argument is that Israel's Health Ministry has stated that the Pfizer now appears to have effectiveness in the 60% range for protecting against infection but still has protection against serious illness and death in the 90% range. 


Sunday, July 11, 2021

Masks and social distancing in the vaccinated elderly

 The CDC, when it lifted its mask recommendation, stated that- in general- people who have been fully vaccinated do not  need to wear masks except in certain situations such as planes,trains and hospitals and contact with the elderly and immunocompromised  They further said that one " should consider" wearing a mask if you have a condition that weakens your immune system" or if you lived in an area of the country where the infection rate was high.(High was not defined by the CDC).The "not wearing masks" was heard and little else was remembered and the take home message was the long awaited "take off your masks".

Remembering back to the early days of the pandemic in 2020 we were told that it was a priority to protect the vulnerable which was taken to mean the immunocompromised and the elderly. 

Were the elderly ignored in the surprise turn around from the CDC's mask guidance? They did not seemed to be specifically mentioned.

In an earlier blog posting I commented about two studies that addressed the immune status of the elderly following Covid vaccination and I wrote the following:

"Muller et al (1) conducted a cohort study on subjects less than 60 years of age and those over the age of 80 who received the Pfizer vaccine. Specific IgG antibody tiers against SARS-COV-2 spike protein were lower in the elderly and the elderly had no detectable neutralizing antibodies. In the younger group 2.2% had no detectable antibodies."

A large Danish Cohort study (2) compared vaccine effectiveness in health care workers and long term care patients. After the second dose the effectiveness in the patients was 64% ( 95% CI  14-84) while in  health care workers the   effectiveness was 95% (95% CI  82 -95. The median age of the 39 040 patients was 84 and there were 488 PCR confirmed cases of SARS-COV 2 cases. If this study can be generalized the widely quoted 90 % plus vaccine efficacy does not apply to the elderly. It should be noted that may well represent the worse case in that the eldely in long term care are a less resilient group that 80 years old independently lived in the community. Note  also sometimes  I am saying effectiveness and sometimes efficacy, they sound alike but in epidemiology they are terms of art and mean different things. More on that below. Also see footnote 1 for explanation of efficacy.

More data on that topic of how well vaccines really work. has  become available.

Jablonska et al (3) published a pre print estimating the " real life " impact of vaccination on covid mortality using data from 31 European countries and Israel from the period from Jan 2020 until April 2021. They found the vaccine effectiveness  in terms of  protection against death was equal to 72%.

Note: The Jablonska article seemed careless  ( it is a preprint after all) in the use of the words "effectiveness" and "efficacy" in that sometimes the authors said effective and sometimes efficacious in reference to their study. In the jargon of epidemiology "effectiveness " refers to real world data , i.e. how a medical intervention in used outside of a randomized clinical trial (RCT)  .The results of a RCT are expressed in terms  of efficacy.   The results of the  RCTs for the Covid vaccines are expressed as efficacy.`

The Danish cohort study and the Jablonska paper were non RCT data and expressed them major metric as effectiveness,


For prevention of severe disease Pfizer,Moderna as well as AstraZeneca and Novavax reported a 100% 
efficacy. 

Why is there such a difference.As the authors suggest age of the populations studied varied.
Only 24.7 % of subjects in the Moderna trial were equal to or older than 65 years of age and 42% of Pfizer trial subjects were over 55 years  of age and only 12.2 % were over  55 in the AstraZeneca trial.


In regards to a medical intervention the disease reducing ability as indicated from the results of a RCT is  always better and correctly expressed as efficacy than that observed when the intervention is utilized outside of the confines  of a RCT and which is correctly expressed as effectiveness. This is very well known .

A number of the public health experts appearing on TV  may have forgotten that when they emphasized  the 100% efficacy against death  that was reported in the randomized trials. It was extrapolation beyond the data to claim or at least hint  that everyone who would be vaccinated would be protected from serious illness  and death. Whether this was intended or not I believe many people were lead to believe when fully vaccinated they were almost guaranteed not to have serious or fatal covid 19 regardless of how old they are on to what degree there may be covid spreading in the community and whether or not that spread may be driven by covid variants such as the Delta variant. 

When I heard repeatedly that the mRNA vaccines were 100% effective against death after the several month duration trials were published I shuddered because I assumed that at least some of those experts knew that the effectiveness of a medical intervention is never at high as the efficacy demonstrated in a clinical trial.  

In early July the Health Ministry of Israel announced that the Pfizer vaccine now seem 65% effective in decreasing symptomatic and asymptomatic disease and 93% effective in preventing hospitalization and death.Several deaths were reported in fully  immunized patients.

From personal experience involving  acquaintances  and family it seems that the  many of the over 75 year old crowd have eagerly accepted the need- no- mask advice since they have been vaccinated and are not known to be immunocompromised and believe that masks and avoiding crowds are no longer necessary.It is not that simple although it was very easy to take away that impression from the CDC announcements.
 
I would have preferred that  the CDC at least  recommend that the immunocompromised consult with their  oncologist or hematologist, a number of which, I believe, are recommending that their patients have their antibody levels checked and in some cases take a third shot. One group in France has taken that approach with their solid organ transplant patients and given third shots which had generally demonstrated a significant increase in antibody levels which were typically low after the standard two doses of the mRNA vaccines.  As for the elderly perhaps they should have been advised to consider the level of vaccination in their community as well as the number of cases of the Delta variant before they go mask free to do things like dining out in inside eateries and attend indoor sporting events.

Of course  the fully vaccinated can gather together for food or singing or whatever and be very unlikely to get sick. This quite different from singing and drinking in bar or a crowded restaurant  in a locality  with 20% vaccination rate and increasing cases of  covid19 from a variant. 

Cases still soar world wide and more have died in 2021 from covid than in all of 2020,India and South America  are hot beds  and cases are increasing in Japan preventing live spectators in the upcoming Olympics  and for lack of vaccine much of Australia is in some form of lockdown.In parts of the world with low or zero vaccination rates variants will develop and air travel links everyone with everyone in the world. The more contagious Delta variant is already over 50% of cases in US and increasing particularly in areas with low vaccination rates.



1)Muller,L et al Age-dependent immune response to Biotech/Pfizer BNT 162b2 COVID-19 vaccination Clin infect Dis 2021 Apr 27

 2)Moustsen-Helms,IR et al Vaccine effectiveness after 1st and 2 nd dose of the BNT162b2 Covid-19 Vaccine in long term care facility residents and healthcare workers A Danish cohort study. Pre Print from Medrxiv 09 March 2021.

3)Jablonske,K et al The real-life impact of vaccination on covid-19 mortality in Europe and Israel. MedRxiv ( this is a pre print and at the time of publication had not been subject to peer review.

 Footnote 1.

Efficacy refers to the proportional reduction in disease attack rate between ARV and ARU, where ARV is the attack rate of the vaccinated group and ARU is the attack rate in the unvaccinated group.

Risk ratio is the ratio of ARV/ARU

Vaccine efficacy is 1-RR expressed as a percentage.

For example if in a given time frame 100 of unvaccinated get the disease and 5 in the vaccinated  group get the disease  we have 1-5/100 = .95 or expressed as a percentage of 95%. 

To put vaccine efficacy in some context we see that in  the 2018-2019 season the flu vaccine has a 29% efficacy .Measles vaccine is about 97% efficacious. 



Thursday, July 01, 2021

The Cures Act,clinical notes and how one well known hospital system complies

 The Cures act mandates that health care providers (HCPs) provide patients access not to just their clinical records but also to the "clinical notes".This refers to the notes that a physician takes during or shortly after the clinical encounter.The initial physician resistance to giving up their clinical notes on the grounds that the patients might not understand the medical terms and jargon had largely dried up by the time that section of the Cures Act finally became in effect.  The Cure Act did much more than mandate that patients can access their clinical notes. The lobbying effort for bill passage was lead by representatives of big pharma and medical device manufacturers.The bill made drug and device approval significantly  easier.

The Act applies all HCPs,health information exchanges and certified IT developers. Fines of up to $1,000,000 you interfere or prevent access or exchange of electronic health information. 

The Act requires that requests for medical information be accomplished "without delay"

Now  as to how one large,big city,well known hospital system complies

We will call the hospital "well known famous place" or WKFP for short and examine how they move to comply with the Cures ACT.

I requested the clinical notes from my primary care internist and from my cardiologist, both of whom are within practice groups which are part of  the WKFP system. Within 48 business hours I received both sets of clinical notes in my patient portal.The shocking number of errors in my internist's clinical notes is a subject for another day.

The most striking feature was the description of a detailed physical exam which both physicians claimed they did but did not actually perform. The Internist's exam consisted of listening to my lungs and the cardiology doc  did not touch me at all. (The usual handshake was eliminated by Covid precautions.)

So the hospital system gets an "A" for delivery of the requested records but an "F" for providing a detailed record of examination that were fabricated. I can not  think of another word to describe claiming that a physical exam was done when in fact it was not. 

Is this done to document an exam to justify the level of Medicare charge they submit? Perhaps so, I cannot think of another reason. Do the physicians involved not worry about this practice? Have the shrewd corporate lawyers found a way to protect this practice from being deemed Medicare Fraud?To my legally naïve eye charging for services not provided would appear to be fraud.(The 20210 changes in Medicare coding seemingly has decreased keying on the exam to upcode visit so maybe there may be no reason to fabricate a physical exam.Maybe that is left over from earlier coding games.)

I have been aware of this ghost exam practice before and have blogged about it. See my blog entry with following title "Has the modern electronic medical record made many physicians accomplices to lying?" Two family members underwent colonoscopies at different hospitals.In both cases the attending physician included in his endoscopy report a detailed physical exam which never happened. Another family member underwent a arthroscopy and appended to that report was the physical exam that was not done by the orthopedic surgeon.

IMO  the modern medical record with all of its electronic snazziness has devolved to be a  embarrassing collection of misinformation, errors and fabricated exams. On the positive side the patient now has a powerful tool-the Curres Act provisions- to obtain his medical record , warts and all. 


addendum: 7/10/21 I had a echocardiogram at 8:am on Thursday. by Friday at 8:p, I received a text that I had a new test results in my patient portal.It was a full report of the echo replete with the data not just the summary. 


Wednesday, June 30, 2021

Is there a U shaped curve relating exercise volume and risk of atrial fibrillation?

 RS Mishima (1) et al reviewed fifteen studies with a total of 1,464,539 individuals from databases of prospective cohort studies to determine the risk of atrial fibrillation (AF) at various exercise levels compared with those individuals who did not meet guideline recommended activity levels.

The current exercise recommendation are at a minimum 450-500 met minutes per week.However, both the US panel and more recently WHO have also said that higher levels, i.e. 2 or 3 times that amount will likely results in greater health benefits. The health benefits are apparent in large epidemiology studies which have demonstrated a curvilinear relationship between exercise volume  and reduction in cardiovascular and all cause mortality.

500 met-minutes per week is equivalent to 2 1/2 hours of moderate (less than 7 METs) exercise or 1 1/4 hours of vigorous exercise. 

While studies of long time athletes have generally shown longer longevity there have also been reports of an apparent increased risk of atrial fibrillation (AF) in endurance athletes particularly those who exercise at levels many times the minimal recommended level .

Mishima found that at exercise levels up to the 2000 met minutes per week level  ( four times the minimal recommended level )there was a decreased risk of AF but "past that point the benefit is less clear".At levels less than 2000 there was a 6 -11% lower risk of AF. At least in this study the upward arm of the U was not found.


 


(1) Mishima,RS  et al Self reported physical activity and atrial fibrillation risk: A systematic Review and Meta-analysis, Heart Rhythm 2020 Dec. 18 

Tuesday, June 22, 2021

Octogenarians and exercise capacity

 The average 80 year old who is healthy has a maximal oxygen capacity of about 20 ml.kilo/min. This is sufficient exercise capacity to finish stage 1 of the Bruce treadmill protocol which requires a 02 uptake of about 17.5. A 02 max of 20 should allow an orthopedically competent  person to walk a mile in 16 minutes. 

The 02 max value of 17.5 ( or 5 Mets) has been quoted as being necessary to be able to handle independent living and a value of less than 7  (2 Mets)  has been considered  considered incompatible with life. (I have been unable to find a reference that confirms that value )

The stylized story of maximal 0xygen uptake (V02 max) and human aging is something like the following:

V02max, heart rate and fat free weight begin to decline around age 25. Multiple studies have demonstrated that the average per decade decline in V02 max is about 9 - 10% while some data suggest that with continuing physical activity the decline may be only 5 % per decade (1)

However, the rate of decline appears to greatly increase after age 65 or 70 as the   curve  becomes curvilinear


Trappe et al studied 55 former elite distance runners after a 22 year period. Their data confirm earlier studies indicating there is a 5-7% per decade  decrease in aerobic capacity even in highly trained athletes. They also found that the subset who did not exercise regularly had a greater percentage decrease in V02max.

Viewed from beneath  the apex there is a systolic counter clockwise rotation of the apex and a clockwise rotation of the base of the heart, likening to wringing out a wash cloth. During diastole there is an untwisting most  of which occurs during the isovolumic relaxation phase of the heart (IVRT).This untwisting represent elastic recoil which is said to be due to the release of restoring forces.Decrease in this suction generation is thought to paly a role in so called diastolic heart failure ., now referred to as heart failure with preserved ejection fraction (HFpEF)

 However, data from Ben Levine's group at the Institute for Exercise and Environmental Medicine in Dallas  indicate that while there is some preservation of left ventricular compliance in those with a history of lifelong exercise ( defined as 25  years or more)  an increase  in IVRT occurred in both  the exercisers  and in the sedentary group.So Levine's data indicate that 4-5 hours of aerobic exercise per week maintained over " a lifetime" will preserve to a significant degree left ventricular compliance but not the prolongation of LV relaxation which accompanies old age.

Tanaka and Seals (3)  in their review article challenge Trappe and other researchers who hold the generally accepted position that regular aerobic exercise will blunt the age related decrease in v02 max. Less controversially  they  suggest that the decline in V02 max is mostly likely due to an age related decline in stroke volume. If  V02  =SV x HR x A-V 02 difference and they claim that there is not a significant decrease in maximal HR  nor AV 02 difference with aging, then only suspect variable left is the stroke volume.

A decreased stroke volume with exercise ties in nicely with the observation that the left ventricular relaxation ( as measured by AVRT  which is the time between aortic valve closure and mitral valve opening) is increased even in highly trained older endurance athletes. With prolonged relaxation time there would be less time for ventricular filling with the increased heart rate associated with exercise , so there is  less LV filling with each cardiac cycle leading to less ability to increase stroke volume with exercise.Add to that the decreased compliance of the left ventricle that occurs with sedentary aging and we can understand at least some of why V02 max decreases with aging.

However, there is more at work with the decrease in exercise capacity related to aging tha nthe decrease in  V02 max.One interesting data point in that regard is the observation that Ed Whitlock marathon times decreased from age 70 to age 82 with there being no change in his measured V 02 max.

At age  70  Whitlock  ran a 2:54 marathon and at age 82 his marathon time decreased to3:41This is a change  from  6.62 minutes per mile to 8.4 minutes per mile or a change from  9 miles per hour to 7.11 miles per hour, a 20% decrease.  Yet during that same time period his measured maximal oxygen uptake was unchanged. We also know from  published interviews  that his training did not significantly diminish. So what was the cause(s) of his decreased running speed?




1)Pollack, ML et al Twenty-year follow-up of aerobic power and body composition of older track athletes

J of App Physio 82 (25) 1508

2) Trappe, SW Costill,DL et al Aging among elite distance runners: a 22 yr longitudinal study

J of App Physiol Vol 80 no 1 285 1996.


3) Tanaka,H Seals,DR Invited review. Dynamic exercise  performance in Masters athletes Insight into the effects of primary human aging of physiological functional capacity.  J of Appl Physiology 2003 vol 95 no 5 2152

So should octogenarians doff their masks and not worry?

 The CDC guidelines now say that for persons who are fully vaccinated they can do most anything mask less. Did the CDC mean everyone ?

Did CDC mean that the  recommendation apply to adults of all ages and what about the immunosuppressed? No, not  for the immunocompromised, but I heard no special mention of the  elderly.

Was there find print in the CDC guidelines? Did everyone just hear the headline?

In general terms both the innate and adaptive arms of the immune system are impaired as a function of age. We know that the flu vaccine, for  example is less immunogenic in the  elderly ,What does fully vaccinated mean for the elderly in particular the 80 and over crowd as relates to covid19 vaccination?

Recently published data addresses that question.

Muller et al (1) conducted a cohort study on subjects less than 60 years of age and those over the age of 80 who received the Pfizer vaccine. Specific IgG antibody tiers against SARS-COV-2 spike protein were lower in the elderly and the elderly had no detectable neutralizing antibodies. In the younger group 2.2% had no detectable antibodies.

A large Danish Cohort study (2) compared vaccine effectiveness in health care workers and long term care patients. After the second dose the effectiveness in the patients was 64% ( 95% CI  14-84) while in  health care workers the   effectiveness was 95% (95% CI  82 -95. The median age of the 39 040 patients was 84 and there were 488 PCR confirmed cases of SARS-COV 2 cases. If this study can be generalized the widely quoted 90 % plus vaccine effectiveness does not apply to the elderly.

So how safe is it for fully vaccinated octogenarians to toss their masks? Is there risk for the 30% who have no  neutralizing antibodies. Going mask less assumes than only the fully vaccinated are going to go mask free? How valid is that assumption. Viewing baseball, hockey and basketball crowds televised from areas in the country in which there is at most 40 % vaccination rate and seeing everyone without a mask leads me to think not very valid.

The Danish and German studies are not the final word but , in my opinion, are sufficient for the over 80 crowd to consider it may not quite be time to throw the masks away and join the crowds.

It has been estimated there are 6 million immunosuppressed patients in the US? How effective are the Covid 9 vaccines in that group? There are sub groups, including organ transplant patients,patients with IBD and with psoriasis and lupus etc  who may be on medications impairing  the immune system. There are also patients on chemotherapy for various hematologic diseases. 

Data is available indicating that some of these patients do not have adequate vaccine mediated immune responses.? A large study from Johns Hopkins found that 46% of solid organ transplant patients had no response to covid19 vaccination. A study from Mt Sinai in New York found good immune response in IBD patients on therapy.

Both the CDC and the FDA have not recommended checking antibody levels nor getting a booster shot if the levels were low or absent. The American Society of Transplantation also agree with that position. Their reasoning escapes me. 

Addendum 6/23/2021 A more optimistic view of the effectiveness of Covid 19 vaccination in the elderly is found here. The article describes national  surveillance data regarding the administration of the Pfizer-BioNtech mRNA vaccine.They report effectiveness of 95.2 to 97.6  %for symptomatic cases in people 85 years of age or older. I am not able to offer an explanation of the large  discrepancy between this study and the Danish data. 


Addendum: 6/26/2021 As of at least 6/25/21 The health authority in Israel has reissued the indoor mask mandate following some cases reports of Covid 19 in fully vaccinated people .At about the same time WHO has stated that immunized people should wear masks  based on concern of the widespread incidence of the Delta ( India) variant. 



1)Muller,L et al Age-dependent immune response to Biotech/Pfizer BNT 162b2 COVID-19 vaccination Clin infectg Dis 2021 Apr 27

 2)Moustsen-Helms,IR et al Vaccine effectiveness after 1st and 2 nd dose of the BNT162b2 Covid-19 Vaccine in long term care facility residents and healthcare workser A Danish cohort study. Pre Print from Medrxiv 09 March 2021.


 





Friday, June 04, 2021

More evidence that the IPhone 12 can significantly impact pacemakers and ICD function

 Dr. Fahd Nadeem and colleagues at Brown University Cardiology studied the effects of the Apple iPhone 12 Pro max model on several pacemakers and ICDs made by Medtronic,Abbott and Boston Scientific, (1)

The iPhone 12 uses a charging device than can charge  wirelessly. It uses a charging bases that generates a magnetic field inducing voltage in the cell phone,

Nadeem demonstrated that placing the iPhone 12 directly over the CIED ( within 1.5 cm  of the unit ) inhibited the  capacity of the ICD to deliver a shock and when placed over a pacemaker caused  the unit to switch to an asynchronous mode.

CIED units are designed to respond to a magnet placed over the unit.It is a feature  and not a bug. An ICD is designed to respond to magnet application by "activation of the magnet mode" which mean that a certain pacing rate is set and the the tachytherapies are inhibited. Simply put, the ICD will not deliver a shock. Pacemakers are designed to respond to a magnet by reverting to a asynchronous pacing mode at a certain rate.The standard donut magnet is sometimes used in surgery when radiofrequency energy is used for cauterization.

Models manufactured by Medtronic and by Abbott  responded to the iPhone as described above but  models from Boston Scientific seemed less susceptible to the magnetic effect of the iPhone.

Magnetic mode activation has been reported to occur with as little a a 10G field magnet.The authors tested the IPhone 12 with a magnetometer and found a magnetic field of  50G.

An earlier study quoted by Nadeem found that an earlier model of iPhone did not trigger magnet mode reversion .

Take home message seems to be do not put an iPhone 12 in your breast pocket if you have a pacemaker or ICD.

Nadeem 's study appears to contradict Apple's advisory stating that the iPhone 12 does not pose a greater risk of magnetic interference than older generation of iPhones. Apple has made a variety of Phones  and the Nadeem article only provided data on the iPHone 12 and by reference the iPhone 6. 


1) Nadeem,F Magnetic interference on cardiac implantable electronic devices from Appl, iPone MagSafe Technology J Am Heart Jan 12 2021. e020818  (full text available)



Wednesday, May 26, 2021

LBBB with left axis differs mechanistically from LBBB with normal axis

 A paper by L. Sciarra et al  (1) presents evidence that LBBB with left axis deviation ( frontal plane axis between -30 and -90 degrees) differs in terms of the conduction sequence  and regional left ventricular contraction patterns. They argue that patterns differs from what is observed in LBBB with a normal axis and suggest that a different approach to CRT is indicated.

Normally, with intact left bundle branch conduction the interventricular septum is activated from left to right. In LBBB the septum is activated from right to left  In typical LBBB there is early activation and contraction of the septum with bulging of the left basal portion of the left ventricle which then contracts late causing a bulging of the septum. Because the lateral LV wall is the last segment to contract it has been thought best to place the coronary sinus lead in a vein draining that area of the heart to optimize CRT.

However, in LBBB with LAD the last segment to contract is the anterior wall of the LV suggesting optimal  CRT might be obtained by positioning the CS lead more anteriorly .

A sub analysis from the MADIT CRT trial found that LBBB plus LAD has an increase risk of Heart failure and death and a trend ( not stat significant ) toward less benefit from CRT.

Speculation - maybe CS leads were not in optimal location.



1) Sciarra, L et al Patients with left bundle branch block and left axis deviation show a specific left ventricular asynchrony pattern Implications for lft ventricular lead placement during CRT implantation.J Electrocardiology Mar-Apr 2018:51,(2) 175 

Monday, May 17, 2021

What does chronaxie have to do with His Bundle pacing?

 What does chronaxie have to do with His Bundle Pacing (HBP), for that matter what does chronaxie have to do with anything?

The minimal voltage amplitude that can capture a nerve or muscle at an infinitely long pulse duration is called the rheobase.More simply rheobase is the minimal voltage necessary to stimulate the tissue. The chronaxie is defined as the pulse duration required for capture with a voltage of twice the rheobase. 

The chronaxie is important in regard to programing pulse generators. The chronaxie approximates the point on the strength duration curve at which there is minimal energy expended. The strength duration curve intersects the energy curve at the chronaxie, where energy equals V2/r X I .


Quoting Ellenbogen, fifth edition " As a practical point when programming the pulse duration of a  pulse generator,chronaxie is an excellent choice to minimize energy,limit charge drained from the battery... 

That sentence was written at a time before there was clinical application of His Bundle pacing. Is there any reason to believe that that rule of thumb would be no longer applicable? Is the chronaxie an excellent choice to minimize energy and limit battery depletion in patients with His Pacing? If so does that apply to both selective and non-selective His pacing?

Dr. Marek Jastrzebski and his colleagues in Krakow along with Dr. Pugazhendi  Vijayaraman from Geisinger Commonwealth School of Medicine (1)have studied the strength duration curves of the His bundle and the adjacent right ventricular muscle and make suggestions regarding programming .

They determined the HB and adjacent Right ventricular muscle chronaxies in 127 patients finding that in patients with selective HB pacing that the His bundle had a shorter chronaxie than the adjacent RV muscle while in non selective HBP patients the RV and HBP chronaxies did not differ.

The authors say that it is their practice to promote selective HB capture by empirically programming the pulse duration  (pd) to 0.2 -0.3 ms.However,for non selective , particularly in cases of distal AV block a longer pd ( i.e. 1.0 ms) would offer greater safety. They suggest that sometimes (often ?) the default setting from the factory is often 1.0 ms, which is far from optimal. 


 

1) Jastrzebski,M et al His bundle has a shorter chronaxie that does the adjacent ventricular myocardium:Implications for pacemaker programming. Heart Rhythm 2019;16:1808-1810.

2) Clinical Cardiac pacing,defibrillation,and resynchronization therapy, Ellenbogen,Wilkoff,Kay,Lau and Auricchio FifthEdition  


Monday, April 26, 2021

Is it safe to do MRI in pacemaker patients with abandoned leads?

 Is it safe to perform an MR in a Pacemaker patient who has one or more abandoned leads? It seems that the conventional wisdom has been that it is not safe.

This article from RD Schaller et al (1) at the University of Pennsylvania  provides reassuring data. They present data on 139 patients in whom 200 MRs were performed without serious events. There were 5 instances of transient decrease in lead sensing and one patient complained of subjective sternal heating.

There were  no changes in battery voltage,or changes in pacing rate. Quoting the authors:

"The growing aggregate of data questions the absolute contraindication for MRI in patients with abandoned CIED leads." The authors also point out that CMS will typically  not reimburse such cases.


(1) Schaller,RD et al, Magnetic resonance imaging in patients with cardiac implantable electronic devices with abandoned leads. JAMA Cardiol. published online Feb 17, 2021. doi:10/1001/jamacardiol.2020.7572

Friday, April 23, 2021

Another battery related recall for Medtronic implantable electronic devices

 

Has Medtronic had more battery related problems than other pacemaker manufacturers or does it just seem that way because of the number of recalls and battery life estimation issues reported in the last 2 -3 years and the fact that Medtronic makes more units than any other company? Medtronic is not alone. both Guidant and St. Jude have had major recalls .

Premature battery failure lead to St Jude's recall of ICDs and CRT-D units involving over 300 thousand world wide with 250000 in the US.Reports indicate that St. Jude knew of the problem for years before the recall. One death was reported in 2014 and a second death in 2016 before the October 2016 recall was issued.St Jude was purchased by Abbott.

A similar narrative can be told about Guidant who became aware of a shorting issue in their Prize II IC which did not allow the unit to deliver a shock while also destroying the  shocking system . Guidant informed the FDA and fixed the problem but did not warn physicians nor patients and continued to sell some units that had not been modified.The Prize was introduced into the market in 2000,  the flaw discovered in 2003 but it was not until  2005 that the company disclosed the problem. Finally in  October 2013 Boston Scientific who had purchased  Guidant pleaded guilty to a false claims act litigation and agreed to pay 296 million dollar fine. 

There were problems with  Medtronic CIED programmers in units made between October 2018 and January 2019 that resulted in erroneous estimate of battery life.These were ultimately corrected and in the end seemed to be really more of an anxiety producing nuisance than a threat. 

Also in 2019 there were three reports of pacemaker batteries being completely drained resulting in one death.This problems involved five different Medtronic models and 131000 units and involved a potential capacitor damage. This situation was troublesome to both EP cardiologists and the patients as there was no way to determine which specific units were likely to fail and pacemaker replacement is not a risk free minor procedure. Having a complicated device under your chest wall skin is anxiety producing enough without the added worry that the type unit you have had been known to suddenly fail. It seems to be a recurrent situation with CIED recalls that there is no way to determine if a particular unit within a class of units subject to the recall is in fact one that is doomed to fail.

On 2/3/2021 Medtronic send an "Urgent Medical Device Correction" letter to all affected physicians.  On 4/12/2021 The FDA announced a recall of about 240,00 Medtronic CIEDS.These are seven models of  CRT-ICDs and pacemaker ICDs. see here for link  This is a class I recall which means a potential risk for serious  injury or  death.

When a Medtronic pacemaker reaches a certain predetermined battery life remaining signal  the device is said to go to a RRT  setting or condition (Recommended replacement time) which sets a 3 month clock ticking before it goes to the next condition which is called ERT (elective replacement time).This condition, which I understand is unique to Medtronic PMs involves a Mode switch  to a VVI mode at a heart rate of 65.

Some devices involved in this latest recall may move from the RRT warning to full battery depletion in as little as 24 hours.There have been over 400 complaints with these devices and 18 "injuries" also reported. Generally PMS do not have a system feature that notifies patient or physician when RRT is reached. I will not know if my PM has reached RRT until a remote  ( or office ) interrogation designates that.(I have a five year old Medtronic model "Consulta"

 Questions come to mind-

Has Medtronic contacted the approximate quarter million patients who have these units or does the letter send to the physicians put the onus on the docs to spread the word?

Does the typical PM clinic have computerized records of which PM each of their patients have? 

A 2017 report from office of the inspector general estimated that 1.5 billion dollars had been paid by Medicare for replacement of 7 different models of CIED in 73,000 patients during the time period 2005-2013.According to the report manufacturers do not typically pay for replacement costs, 

Medtronic has also had recalls recently for its HVAD units (see here) and its blood pump (see here)


Wednesday, April 14, 2021

Complications from Left Bundle Branch area pacing

 Chen et al (1) report their experience in 612 LBBA implantations from 2018 to  2020 .Mean time of followup was 12.5 months.

Complication rate was low. and consisted of:

2 post operative septal perforations,2 post operative lead displacements ,4 intra operative septal injuries and 2 intra operative lead fractures,none of which had serious consequences.


1) Chen, X. Procedures-related complications of Left Bundle pacing: A single center experience. 

frontiers of Cardiovascular Medicine,24 March 2021. Full text is available on line. 

Monday, April 12, 2021

What is the mechanism of left axis deviation in some cases of Left bundle branch block?

 Dr. Saer Abu-Alrub et al (1) offer one explanation for  the occurrence of left axis deviation (LAD) in some cases of left bundle branch block (LBBB).

Twenty nine patients with non-ischemic cardiomyopathy were studied with non invasive cardiac mapping, CT and MR imaging .Sixteen had a normal QRS axis while 13 had LAD .The LAD group demonstrated delayed activation of the basal anterolateral region.The LAD group demonstrated an apex to base activation pattern versus a circumferential pattern observed in the normal axis group.

 Imaging studies demonstrated no differences in cardiac structure between the two groups so the investigators concluded that LBBB with LAD was a "purely electrical phenomenon".

Some LBBB patients with LAD  treated with CRT ( either by BIV or conduction system pacing)have normalization of the QRS duration and of the electrical axis while others have only the QRS normalized with the left axis unchanged. I have been unable to find any explanation of that. 



1) Abu-Alrub,S et al Left axis deviation in patients with non ischemic heart failure and left bundle branch block is a purely electrical phenomenon. Heart Rhythm, 2021 April  33831543

Do some patients with idiopathic left bundle branch block have an underlying cardiomyopathy?

Janek Salatzki and co workers (1) present evidence that there may more at work in idiopathic LBBB (ILBBB) than simply dysynchrony. It is generally accepted than LBBB alone can cause heart failure (HF) and myocardial remodeling. Salazki present data using an innovative technique,determination of septal flash volume, which they believe suggests that a contractile impairment is a necessary condition for remodeling while dysynchrony alone may induce heart failure.

The authors state that another explanation for their data is that the LBBB group with remodeling were simply patients who had the LBBB longer. The retrospective nature of their data does not enable them to exclude that alternative.

The first description of ILBBB causing heart failure was in 2005 and one of the speculations at that time was that there was an underlying cardiomyopathy , i.e. it just was not simply the dysynchrony operative in causing HF to develop but a disease process affecting both muscle and conduction fibers.The various case series demonstrating a favorable and often super respond in lone LBBB patients treated with either  BiV or conduction system pacing  suggests that desynchrony is the dominant problem.  

1)Salatski,J et al Presence of contractile impairment appears crucial for structural remodeling in idiopathic left bundle branch block Journal of cardiovascular resonance.2021 april 23 

2). Blanc J et al. Evaluation of left bundle branch block as a reversible cause of non-ischemic dilated cardiomyopathy with severe heart failure. A new concept of left ventricular dyssynchrony-induced cardiomyopathy. Europace 2005;7,604

Friday, April 09, 2021

Left bundle branch area pacing as alternative for bi-ventricular pacing for refractory heart failure

 Should cardiac conduction system pacing replace bi-ventricular pacing for patients with refractory heart failure (HF)? The two forms of conduction system pacing are His bundle pacing and left bundle branch area pacing.

Vijayaraman et al(1)have  published the results of a retrospective multi center study to asses the feasibility and outcomes of left bundle branch area pacing (LBBAP) in patients as an alternative to bi-ventricular  pacing (Bi-V). See herehttps://www.jacc.org/doi/pdf/10.1016/j.jacep.2020.08.015

LBBAP pacing was attempted in 325 patients and was successful in 277 or 85%.LBBAP resulted in significant shortening of the QRS,clinical and echocardiographic improvement, and was achieved with low thresholds and adequately high R waves. In short, LBBAP seemed feasible and safe. No mention was made in the abstract regarding septal wall perforation an event that had been reported in some earlier case series. 

Among clinical indications for pacemaker implantation none equal the randomized clinic trial data supporting CRT using BIV.

There are observational data supporting the value of both His Bundle pacing and now LBBAP as an alternative to Bi V pacing. I think  a large RCT would be necessary to demonstrate superiority or more likely non-inferiority  of cardiac conduction pacing versus BiV.Where would funding for that be found?



1)Vijayaraman,p et al Left bundle branch area pacing for cardiac resynchronization therapy:Results from  the International LBBAP collaborative study. JACC Clin EP archives, vol 7 no. 2 135-137. 

  

Wednesday, April 07, 2021

Implantation of both His Lead and LBBA lead in atrial fibrillation patients

 In the early days of His bundle pacing (HBP) there was a issue of whether or not a backup lead should also be implanted.This controversy has apparently not been completely resolved and may have regained some steam as reports have appeared indicating  that some not insignificant number of His  leads develop high thresholds over time  even though the initial threshold was appropriate.

Yand Ye et al (1) describe an interesting variation of using a backup in conjunction with a His Lead.They studied 16  AF patients who were pacemaker dependent in whom they attempted to place both a His lead and a left bundle branch area lead.(LBBA).The His lead was the primary pacing lead and the LBBA lead was considered the backup lead. Thirteen of the sixteen were successfully implanted. Although the results section of the paper is somewhat unclear apparently at least one patient had a increase in the capture threshold leading to switching to the LBBA lead. During the six month follow-up there were no lead dislodgments or ventricular perforations.There have been a few reports of late perforations of the  LBBA pacing lead.

The authors conclude that the technique is doable and safe and may offer an approach at least for PM dependent patients with AF.In this group of patients the rivalry between HBP and LBBA pacing could be avoided.Maybe not a either or but a both.


1) Yand Ye, Feasibility and safety of both His Bundle Pacing and left bundle branch area pacing in atrial fibrillation patients: intermediate term follow-up.Journal of interventional cardiac electrophysiology. 2021 March 15 33723691






Tuesday, April 06, 2021

Does location of His lead (above or below the tricuspid valve) matter?

 A study of fifty patients by Y. Hu et al (1)  indicates that it does matter. Two problems with His pacing are higher capture threshold voltage are needed and lower R waves . Hu's data indicate that in the 25 patients who were implanted below the TV there were lower ventricular capture thresholds and higher R waves.Echo studies showed no tricuspid regurgitation.

 Somewhat different results were reported by Tang et al (2) in that they found capture voltage to be no different in the atrial leads  compared to the ventricular lead placement in a study of 13 atrial placed His leads and 16 ventricular placed leads. However, they also found that the R wave sensing values were higher in the ventricular lead group with values at implant being 1.87 V for the atrial lead and 4.53 V for the ventricular group. 


Also it is generally thought  in cases of AV block that a sub valvular implantation may be preferred  and that non-selective His pacing may to preferable to selective because it can be its own back up. 


 1)Hu,Y Electrical characteristics of pacing different portion of the His bundle in bradycardia patients 

Europace,2020 December 26, supplement ii 27

2)Tang, C Effect of implantation site of the His bundle pacing leads on pacing parameters a single center experience BMC Cardiovascular disorders. 2021 Feb 24 2021 (1) 112, 

His Bundle pacing can normalize ventricular activation but can it also actually reconstitute native intrinsic conduction ?

His Bundle pacing  (HBP) has been known for years to be capable of normalizing bundle branch blocks. By normalizing I mean that the QRS while the patient is being paced becomes normal with Selective HBP and nearly so with non selective HBP. By reconstitution I mean that the QRS remains normal after HBP is turned off.  Reconstitution  is what authors of 2 case reports document in a article in Heart Rhythm Case Reports.

Dr FM Ezzeddine at al  (1) report two case in which patients with long standing conduction defects were implanted with His leads and after several months of treatment with His bundle CRT  were noted on routine testing  to have resolution of their conduction defects.One patient who had an av block and LBBB had resolution of the AV block while the LBBB continued and the second patient had restoration of normal ventricular conduction no longer having an LBBB pattern. Both patients experienced a significant resolution of their heart failure symptoms when His bundle paced CRT was begun.

Quoting the authors with my underlining.

"His Bundle pacing can restore native intrinsic conduction in some cases after years of chronic conduction block". ..    this demonstrates new theoretical benefits of HBP , the ability to promote conduction down the native pathways that were previously non-conducting." 

 What I  believe  the authors are proposing is that  His bundle pacing had somehow brought about  electrical remodeling  leading to a condition in which pacing was no longer needed to bypass or override whatever specific type of conduction defect the patient had experienced. They consider mechanisms such as Wedensky facilitation which refers to an impulse arriving at a blocked zone and increasing the excitability of tissue beyond the block. Other electrophysiologic speculations are offered.

There have reports of exercise induced LBBB and intermittent rate related LBBB but the authors believe these are the first reports of long standing conduction defects that recovered native conduction following continuous His bundle pacing.

On page 412 of Serge Barold's illustrated guide to pacemakers and resynchronizatio (2)n  the authors suggest there is value to periodically "expose " the underlying spontaneous EKG. This was said in the context of followup on bi-ventricular pacing but perhaps Ezzeddine's paper offers a reason to do that for patients with LBBB who are being His bundle paced.   


 

1) Ezzeddine, FM et al Reconstitution of native intrinsic conduction in patients with chronic conduction block with His bundle pacing. Heart Rhythm Case Reports.2021 1-5,  https;//doi/org/10.1016/j.hrcr,2021.03.006

note: The same cases were presented as a poster, at the JACC meting march 20,2018 by Dr. Ezzeddine

2) Cardiac Pacemakers and Resynchronization , step by step  An Illustrated guide. Second Edition,

Bakrold,SS, Stroobandt, RX adn Sinnaeve, AF 

Sunday, March 28, 2021

Some Pacemaker program features do not work well with His Bundle Pacing

 Some pacemaker programming features do not work well with His Bundle pacing and may cause some  problems raising the question of why have pacemaker manufacturers  not developed programs and algorithms specific to His Pacing . 

In particular the automatic  capture threshold determination(ACM for automatic capture management) program may give falsely high thresholds leading to  setting the capture voltage safety factor too high leading to premature battery depletion as illustrated in a case report referenced later in this article.

If the His lead is placed in the ventricular port (pulse generators used with CRT have three ports) the ACM  which is based on the evoked potential will indicate the RV capture threshold , i.e. not the His threshold. If the RV threshold is higher than the His threshold then the ACM determination will be falsely high. If ,by chance the right ventricular evoked potential is approximately the same as the His potential then ACM works just fine , except you don't know if it working right or not. 

If the His lead is in the LV port, since it is based on the LVP-RVS conduction times the threshold will be that with lowest value either RV myocardial or His. 

The ventricular capture program is activated nightly at 1:am and if unsuccessful another attempt is made every half hour.

Articles by Vijayaraman and Burri has explicated the problems with automatic capture algorithms and HBP and the basic recommendation is that those features be turned off or at most turned to monitor. 

Quoting Vijayaraman, 2018 JACC ;" Utility of automatic threshold testing feature is limited in HBP. In patients with selective HBP  due to lack of evoked potential,this feature may fail to detect the true  His capture threshold. On the contrary in patients with nonselective HBP this feature will detect myocardial capture threshold rather than His bundle capture. " 

Quoting Starr and Burri (Heart Rhythm 2019)

"The RV capture management algorithm of Medtronic devices considers an RVS event that occurs in the 110 ms window following pacing to be V capture ( i.e. it does not specifically detect the evoked  potential)." The authors  then explain that in cases of RBBB selective His Pacing  may have the erroneous diagnosis of non capture  could if the pace capture interval falls outside of the 110 ms window.

Quoting Burri,(2019) ;

"RV capture management algorithms are based on detection of the evoked potential which is absent in case of selective his bundle capture.Even in the case of non-selective capture, the algorithm seldom yields accurate results and the feature should either be inactivated to switched to  "monitor"


The following case report illustrates one undesirable clinical outcome when the ACM is set to "program" but fortunately the problem was quickly corrected.

Wu et al ( 1) report a case in Clinical Case reports in 2020 in which the Medtronic capture management algorithm caused a large and inappropriate increase in the voltage setting.The patient was a 72 year old man with a second degree heart block who was implanted with a His Lead resulting in selective His pacing with an initial Voltage of < 1.5 volts at 0.4 ms.However the next day the EKG now showed nonselective His pacing pattern and the Voltage was set at 5.00V at 1 ms.

 The authors believe that the automatic capture management system which was set on  the factory default setting of adaptive repeatedly noted "pacing capture loss" and reputedly increased the RV voltage. The treating physicians recognized the problem and changed the ACM setting to monitor before significant battery depletion had occurred.

It is not possible from the case report to know  when this event occurred .There were two articles published in 2019 that called attention to problems with the adaptive setting for automatic capture management systems such that the adaptive setting should not be considered the default position. 

As of this writing there seems to be no IPG (PM) specifically designed for His pacing nor is there an automatic capture threshold program designed for HBP. I wonder how often various pacing settings are just left to the factory settings when a PM is implanted with His pacing  even though there is information available in the literature indicating  that  a device features that worked well for right apical ventricular pacing  will not work in His-bundle pacing. 


1) Wu, Jung-Pin et al Automatic capture management may cause   unnecessary battery depletion in selective His Bundle Pacing Clinical Case Reports 2020. DOI 10.1002/ccr3.3168

Thursday, March 25, 2021

Take home messages for "lone " Left bundle branch block


Introductory and personal note

Five  plus years ago I experienced a sudden decrease in my exercise ability.As a long time marathon runner I was well aware of running times and perceived exertional sensation for various speeds. My running times decreased by about 15% (comparing times for a one mile run at a comfortable pace).

My EKG at my  internist's office show an LBBB pattern. Neither he nor I were aware of the significant exercise impairment that can be caused by LBBB. A number of web sites even now offer misinformation about LBBB.  Over the past five years there has been much learned about LBBB,His Bundle Pacing,and the potentially harmful effects of pacing the heart from the right apex, and the entity of LBBB induced cardiomyopathy. 

 I also had developed an exercise induced high grade second degree heart block for which I received a pacemaker ( PM) importantly with a Bundle of His lead  (HB)  After recovery from the implantation  procedure I was able to return to running with an apparent recovery to my pre LBBB level. A number of blog readers have contacted me about exercise problems similar to mine and their frustration with the medical advice from their cardiologists. I was evaluated for coronary artery disease and none was found.(see endnote 1)

The following is a recap of what I have learned about LBBB and related  matters which may be of interest at least to folks with that condition. It is not offered as specific medical advice and is just my take on a subject of obvious great personal  importance from a non-cardiologist who over the last five years has enjoyed a non-sanctioned,personal,perhaps quiky ,self directed mini fellowship in electrophysiology. 
____
All LBBBs are not created equal. Even the subset of lone LBBB is not homogenous.

About half of patients whose EKGs meet standard  criteria for LBBB are shown to have a particular pattern on echocardiography.This seems to be the case whether the standard criteria are used or the more stringent Strauss criteria.(see end note 2)

This echo  pattern describes an abnormal,out- of -sync contraction pattern of the left ventricule (LV)
It begins with a electrical activation of the interventricular septum from right to left  (opposite to the normal direction of septal activation) and then a swift leftward movement of the septum and a bulging out of the left lateral ventricular wall,followed by a delayed LV wall contraction and rightward bulging of the septum.The septal movement occurs before the aortic valve opens (in the isovolemic contraction phase when mitral and aortic valves are closed as pressure builds up to snap open the aortic valve).Some ,but not all, patients with an EKG pattern of LBBB demonstrate this pattern on echocardiography or Cardiac MRI studies

This same pattern has been observed in  at least some cases of RV apical pacing.


Cramer and De Boeck (1)et al describe this mechanism by which abnormal electrical activation leads to abnormal contraction-a dyscoordination of contraction in at least many cases of LBBB.

 " This discoordination encompasses regional differences in timing,duration and amplitudes of contraction.When the differences are large enough,part of the contractile energy of the early contracting segments will be dissipated into abnormal stretching of remote areas during early systole and vice versa at end systole...The decreased global pump function will activate neurohormonal response mechanisms in an attempt to maintain normal cardiac output,favouring ventricular dilatation and remodeling. "




In some patients, LBBB is not associated with this pattern and in these it may be that electrical signals are merely delayed but occur in the normal left to right pattern .Several patterns of septal motion have been described.

The resting echo typically demonstrates no problem other than an ejection fraction (EF) that might be at the lower limits of normal and in the absence of a earlier higher value carries little diagnostic value.However some work indicates that the ejection fraction is not  accurately measured in LBBB using the Simpson method and that the "true" EF is lower than measured.

It should be noted that it may be possible to recognize the early left ward motion of the septal on echo and has been named "septal flash".Patients with this septal flash pattern generally respond well and sometimes exceptionally well with CRT-either with traditional bi-ventricular CRT or with His Bundle pacing.

With exercise, stroke volume fails to increase ,diastolic pressures rise and the patient may become short of breath. Human and animal work have demonstrated that   increased afterload (as with increased blood pressure) and increased heart rate cardiac function decreases significantly including decrease in EF.

A patient presenting to a cardiology clinic with LBBB,no symptoms and a negative evaluation for coronary artery disease would likely be reassured and followed.

A symptomatic patient poses a more difficult problem.If he had a normal echo some docs  would just follow the patient , a management plan not likely to be well received by an endurance athlete.If the patient had reached  a phase of cardiomyopathy with evidence of heart failure, the usual medications would likely be prescribed .However reports indicate that the usual goal directed therapy GRT) is not effective in LBBB induced cardiomyopathy.Some authors have suggested that earlier  (that is less than the standard three month  trial of GDT) pacemaker therapy should be used.

Five years ago His Bundle pacing was not a routine  procedure for PM implantation- now it has become the default procedure in a number of centers for AV block and for sinus node disease and for pacing after A-V node ablation and in some centers the preferred approach for CRT instead of Left ventricular pacing through a lead in the coronary sinus.

Although by 2000 there was great interest and enthusiasm for HBP  and had become a II A AHA/ACC/HRS guideline recommendation, more recent analysis of data from HBP follow up has revealed perhaps as many as a quarter of  successful His bundle  implantation with adequately capture voltages  over time increase voltage requirements to levels which likely will lead to premature battery replacements.This in part has lead to increasing acceptance of another,newer form of conduction system pacing namely pacing the left bundle  directly by advancing a lead further into the RV apex and screwing in a lead deep into the septum. As of this writing bundle branch area pacing has become popular in China, it s country of origin, and also apparently used a a primary means of pacing  in place of HBP at Virginia Commonwealth Medical School according to a recent article by Padala and Ellenbogen (2). As best I can tell as an outsider, some form of conduction system pacing has largely replaced the traditional pacing from the right ventricular apex. 



1 Cramer,MMJ and De Boeck, BW Three dimensional echocardiography and left bundle branch block:Prime time in cardiology. Neth Heart J 2007 Mar 15(3) 87

2) Padala, S and Ellenbogen KA  Left bundle branch pacing is the best approach to physiological pacing. Heart rhythm ,2020 


end note 1

As was the party line recommendation at the time,coronary disease was evaluated by a stress echo in a patient with LBBB.Abnormal movement of the interventricular septum,decreased septal blood flow not caused by obstructive disease and abnormal changes on the ekg generally make various testing methods less than optimally reliable, eg.regular treadmill exercise  and some isotope tests. The SPECT myocardial perfusion imaging is a problem because of septal perfusion defects occurring in patients who do not have obstructive lesions in the Left anterior descending artery. The stress echo test is popular in some centers but a recent review from the Cleveland Clinic discredits the stress echo considering it unreliable and favors CT angiography if patients  less than 65 and the pharmacologic nuclear imaging or dobutamine stress echocardiography if over 65 years of age.Older patients are more likely to have coronary calcification making the CT  angio less useful. (.https://consultqd.clevelandclinic.org/in-patients-with-left-bundle-branch-block-whats-the-best-test-for-cad/)


end note 2

Strauss criteria for EKG diagnosis of LBBB- QRS greater than 140 msec in males,and greater than 130 msec in women and mid QRS notching in 2 contiguous leads.(Strauss,D Defining Left bundle branch block in the era of Cardiac Resynchronization Therapy. Am J Cardiology 107 (6)2011