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 ...

Thursday, December 30, 2021

Status report Covid 19 in Texas at end of 2021

 From my vantage point in Houston everything I see here validates my decision to urge a relative not to travel here  from Paris for Christmas. 

Cases soar and  emergency rooms are packed,Drug stores have sold out of the home antigen tests and the state is out of (or almost out of ) the only antibody treatment that is effective for Omicron (sotrovimab). Houston's county health agency urges people to not go to the ERs to get a covid tests and to use masks in congregate settings.

The Texas Medical Center reported for the week of December 20th a positivity rate of 15.4 % versus  6.2% for the previous week and  201 Covid admission versus 101 the previous week. 

The two prescription medications approved by the FDA for out patient treatment of Covid 19 are yet to arrive in the state . A number of eateries have closed due to the lack of staff and New Year's Eve is approaching and from what I see mask wearing is not prevalent, The Christmas church services  whose live streams I sampled did not seem to require masking in spite of the recommendation of the CDC and county health authorities. By contrast the Pope's Christmas mass had everyone wearing a mask. 

On a positive note, a number of centers have been designated to administer Evusheld, This is an antibody cocktail to be given IM every six months to prevent infection in immunocompromised patients which received an EUA in early December.

President Biden has just said there is not a "federal solution" to the developing crisis and defers to the state Governors. Residents of Texas may find little comfort in that as Govenor Abbott has by executive action and legislation taken steps to minimize masks use by schools and vaccine mandates by state schools and by businesses. I hope  I am wrong but Texans are not likely to see Covid mitigation actions coming from Austin. By contrast the govenor of Connecticut  has ordered the national guard to  distribute N 95 masks and antigen test kits.

Apparently both the Delta strain and the Omicron variant are circulating, one being much more contagious and the other more virulent  and physicians have no quick way of distinguishing between the two. 

All we can do is pull up the draw bridge and hope to not have a medical emergency and not deplete too much psychic energy lamenting and asking the question how  could the richest country in the world end up where we are now. 

Addendum 12/31/21.As of 12/31/21 Walmart and Sam's Club Pharmacies in Texas have both Paxlovid and Molnupiravir available with prescription from physician. 

Thursday, November 18, 2021

Without durable individual immunity you cannot even talk about herd immunity

 In the early days of the covid 19 pandemic there was much speculation about what percent of the population would have to be vaccinated in order to achieve herd immunity )(HI). It seemed to be a matter of not if but when HI would be accomplished.

Writers made analogies to  measles and smallpox for which vaccination programs achieved herd immunity and in the case of smallpox, eradication. If HI could be achieved  for a  very infectious disease such as measles spread by aerosols, why not covid 19?

Theoretical considerations regarding HI center on the basic reproduction number (R naught or Ro which is the average number of people that one infected person will infect.  The number of people needed to be immunized in order to reach HI is 1-1/Ro.For example-if the Ro is 2 then 50% would have to become immune (either through vaccination or infection) for a Ro 0f 3 we see 1-1/3 equals 2 thirds or 67% 

Several simplifying assumptions underlie the formula for HI including that all individuals have an equal opportunity to become infected. Epidemiologists disagree as to what exactly HI is and as to what the necessary assumptions are in estimating a HI vaccination level.

However the key-typically implicit- assumption is that being vaccinated ( or recovering from an infection) results in long lasting immunity.(1)

We now know that this major assumption does  not conform with reality. We now know that fully immunized individuals can become infected and can transmit the disease and also  that recovery from covid 19 infection does not preclude becoming infected again. 

The idea underlying HI is that as individuals become vaccinated ( or recover from infection) they are removed from the susceptible pool. With covid vaccination or infection  both groups seem to be removed from that pool only for a time , perhaps as short a time as 6-8 months. While infection blocking immunity (nasal mucosal immunity) wanes quickly the disease reducing immunity seems to be more durable.

When cases of abreakthrough infection became recognized as a real thing,some in the public health sector  said  " well, the vaccine was only intended to prevent serious disease and death".But if that were the case why was there so much  talk about achieving herd immunity a concept that IMO only makes sense if the vaccine prevents spread.

Dr Jennie S Levine has been quoted that she and her colleagues talk about transient herd immunity.

My thought on that is perhaps we are seeing a transient HI for example now In Louisiana and Texas .Both states had a major Delta surge with a surge of cases and hospitalization and death and now the surge seems to have abated.Possibly as more and more people were vaccinated and more infection plus mandatory NPIs (in Louisiana ) the number of susceptible individual decreases to reach some level of transient herd immunity like condition. However, as immunity wanes again in states with a large number of unvaccinated individuals serving as a covid reservoir some level of spread could occur again  for another round of surges . Are we likely to continue to see regional whack a mole events .

A much more optimistic scenario is that the booster shots will bring about a sufficiently long period of immunity so that more than a transient herd immunity could be achieved. In other words- the covid 19 mRNA vaccine should have been a three shot vaccination  program all along.  

1)Core Concept: Herd immunity is an important—and often misunderstood—public health phenomenon | PNAS

Thursday, November 11, 2021

How big will the US covid winter surge be?

The epidemiology  predictors at IMHE made their prediction for the 2021 winter on a tweet published November 5.

Based on three factors they predicted there will be a winter surge but, of course its magnitude is unknown.
The factors are : 1) seasonality 2) waning vaccination immunity 3)less caution by the public,We think we know the direction of these vectors but what about their magnitudes?

As time goes on not only vaccine immunity will fade but so will the immunity of previous covid 19 infection  both of which seem to fade in about six months.   Countering that direction is the number of people receiving the booster shots.Countering that is the relentless barage from right wing media claiming that the vaccines are either dangerous or worthless.

Meanwhile in France and Germany a new surge seems underway and travel restrictions to to the US have been lifted. What could possibly go wrong?

Dr. Michael Osterholm is quoted: "Any effort to predict future course beyond 30 days relies on pixie dust for its basis" and we all remember what Yogi said about predictions particularly for the future.

Monday, November 08, 2021

Cardiac fibrosis in endurance athletes

 There have been a number of reports of cardiac fibrosis in endurance athletes. It turns out that these reports pertain to areas of late gadolinium enhancement in right ventricular insertion points.Some explanation is required . To begin with-all forms of fibrosis are not the same.

Gadolinium is the contrast agent  used in MRIs.It accumulates in the extracellular space and lights up on a cardiac MR and is called Late Gadolinium Enhancement (LGE)

LGE is seen in myocardial infarctions in necrotic areas with scars consisting of replacement fibrosis.LGE has also been reported in hypertrophic cardiomyopathy (HCM) ,pulmonary hypertension and more recently in a number of long time highly trained endurance athletes.In these three conditions the underlying pathology is not replacement fibrosis  (as is seen in a myocardial infarction scar) but rather plexiform fibrosis and myocardial fiber disarray and is typically seen at the insertion points or hinge points where the right ventricular wall inserts on the interventricular septum. 

Sato et al (1) proposed  that paradoxical motion of the interventricular septum is a primary mechanism for late gadolinium enhancement (LGE) at the ventricular insertion or hinge points.

LGE at ventricular insertion points has been described in pulmonary hypertension and in a number of highly trained endurance athletes .It is unlikely that paradoxical septal movement explains the LGE at hinge points in these athletes although it may be  true in the cases described by Sato.

DeBosscher et al (2) found LGE at the hinge points in young and older highly trained endurance athletes but found no evidence that LGE was associated with any structural,functional or electrical problem with LGE at the insertion points which they found  28% of the 233 athletes studied.

LGE was first described in  older endurance athletes   but now this data demonstrates that younger runners may also have that finding and that it is not a uncommon findings in highly trained runners and its long term significance remains to be determined. I suppose the fact that the LGE does not represent replacement fibrosis  with its associated risk of reentrant ventricular tachycardia  is good news.However,data is lacking as to the long term consequences (if ANY) of LGE at the RV insertion points in long time endurance athletes regarding reentrant rhythms or other clinical problems. 

1) Sato,t et al Paradoxical motion of the interventricuar septum as a primary mechanism of ate gadolinium enhancement at ventricular insertion points. Int J Cariol 2012;158 (1) 156-7 

2)De Bosscher, R et al Hinge point fibrosis in athletes is not associated with structural, functional or electrical consequences;a comparison between young and middle aged elite endurance athletes. Euro Heart Journal, 41,supp 2, Nov 2020 

Friday, November 05, 2021

What is the threshold for exercise induced cardiac remodeling (EICR)

 It has been known for over 100 years that physical exercise  may cause heart enlargement.A study of Harvard rowing team members described cardiac enlargement in an 1899 issue of the Boston Medical Surgical Journal.  

There have been numerous cross sectional and longitudinal study documenting the structural changes in the heart associated with high levels of aerobic exercise.These  are enlargement of all four chambers and mild to moderate increase in the left ventricular wall thickness and an increase in left ventricular mass index- a condition referred to as eccentric hypertrophy to be distinguished from the concentric hypertrophy characteristic of strength building exercise. 

How much exercise is required to bring about that remodeling? Is  eccentric remodeling observed in runners whose activity  level is far less that that required  to be competitive in a full triathlon ?

Dawes and associates  (1) have provided some answers.They performed cardiac mri s on 1096 volunteers and linked  the mr results with their self reported exercise habits over the previous 12 months. They divided the exercise histories into four categories with category 1 being essentially no regular aerobic exercise and category 11 defined as less than or equal to 3 hours per week. They found that there was no statistical difference between category I and category 11 in regard to cardiac MR findings/

So one 'take- home" from their study might be  that exercise less than 3 hours per week is not likely to be associated with any exercise related structural cardiac changes. 

Moreover they found that increasing activity levels were significantly associated with increased ventricular end-diastolic volumes and left ventricular mass index

However, minutes exercised is not the only variable related to EICR which is likely related to some summation or interaction between intensity, frequency and duration. One could speculate that someone doing 3 hours of high intensity interval training per week  might well induce a bit of EICR and that someone doing 8 hours of slow walking in the park per week may probably would not

1) Dawes TJW Moderate physical activity in healthy adults is associated with cardiac remodeling.Circ Cardiovascular imaging 2016  se004712  

Friday, October 01, 2021

Has the conservative- libertarian "fusion" been severed by Trumpian authoritarianism ?

 Aaron Ross Powell from Cato Institute writes about the  always fragile "fusion" of conservatives and libertarians becoming increasingly severed. He refers  back to Robert Nozik's observation that  " Liberty disrupts patterns" as at least a partial explanation. 

Conservative- preferred social patterns are disrupted by liberty  So to maintain those patterns conservatives turn to authoritarian means , if not they loose their conservative values. 

What are these conservative values? They generally include family values which mean a man-woman stable relationship,opposition to gay unions,opposition to abortion and a tending to endorse traditional female roles in society, allegedly based in and supported by biblical principles. Additionally conservatives  endorsed  a society that is  largely managed and controlled by white anglo saxon men with opposition to encroachment by black and brown immigrants, preferring things as they once were or  were thought to be at some vaguely defined prior time.

Progressive big government with its ever growing body of liberty limiting regulations is a common foe for conservative and libertarians with conservatives bristling  at bureaucratic rules antithetical  to conservative's preferred social norms and libertarian obviously promoting liberty.

Decisions once made by families and local governments have been shifted to state and then federal government as the locus of decision making, a development well described and critiqued by Thomas Sowell in his book "Knowledge and Decisions ". This central decision making  shift is another common foe for conservatives and libertarians.

Arnold Kling offered a framework for considering the differences between the languages used by progressives,conservatives and libertarians Progressives tend to frame things as there being a battle between the oppressed and the oppressors, while conservatives see things as between civilization and barbarism while libertarians view matters as between liberty and coercion.

In answer to the title question-No Trumpian authoritarianism   did not break the conservative-libertarian fusion as it was a fragile union to begin though arguably useful regarding  certain issues   but his rhetoric may have provided a effective rallying cry (MAGA) and gave the nativists' core of conservatism a person around whom  to rally.

I believe the key insight in Powell essay is that liberty disrupts patterns and conservatives hold certain societal patterns to be important which are put at risk by liberty so conservatives have to jettison liberty to protect their values. In the terminology of Kling the issue  framed for conservatives is barbarism versus civilization and sometimes liberty must be sacrificed to fight off barbarism.Quoting Powell " conservatives have to restrict liberty to retain their social and economic patterns.".

Tuesday, September 28, 2021

Korean study shows a positive and graded association between physical activity and coronary artery calcification

 A large prospective study (1) from Korea demonstrated a positive relationship between self-reported physical activity and coronary artery calcification (CAC) scores.

There is overwhelming epidemiological evidence that regular exercise is associated with decreased risk of cardiovascular and all-cause mortality.Data indidcate that small amount of exercise is beneficial in that regard and that more seems  better.A panel in 2018 recommended as a minimum 500 met hours per week which is equivalent to 2.5 hours of moderate exercise or 1.25 hrs of vigorous ( greater than 7 Mets) exercise.

Eijesvogel in his comprehensive analysis of the " extreme exercise hypothesis" noted  that the maximum reduction in CV morality was noted at 41 Met hrs per week which is five times the minimum recommended level.  So there is a well defined linear relationship between exercise volume and CV mortality and so far data have not indicated a J shaped curve in that regard.

Defina et al (2) demonstrated that high levels of physical activity ( 3,000Met min per week which is five times the minimum 2018 recommended level) was associated with  prevalent CAC but was not associated with increase in CV disease mortality..Other publicaions have  also demonstrated an increase in coronary calcification in long time endurance athletes .

Sung's article now provides a "positive , graded association between physical activity and progression of coronary calcification, regardless of CAC scores". 

Quoting Sung ;"The standard Agatson CAC scores are calculated as a combination of calcium density and the volume of plaque burden. Higher calcium density,which suggests a more stable calcified plaque, produces a higher CAC score, however it is associated with lower CAD risk."

Both long time endurance exercise and long term use of statins are associated with increased coronary artery calcification  but  lower CV morality.

1)Sung,K et al Physical activity and the progression of coronary artery calcification. Heart 2021;0:1-7,

2) Defina,LF at al Association of all-cause and cardiovascular mortality with high levels of physical activity  and concurrent coronary artery calcifications,JAMA Cardiology, 2019 42 (2) p 174