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 

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.
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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 it 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

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 

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. 

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.