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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 ...

Friday, April 14, 2017

If peak load is the determing parameter runners should have more osteoarthritis

Perhaps it seems counter intuitive that runners do not have a higher incidence of knee osteoarthritis or so the preponderance of epidemiologic data contents.After all the peak load of the articular cartilages in running is much higher than in walking or so the kinesiologists tell us and would not the cumulative higher peak load after many miles of running wear out and maybe chew up the articular cartilages.

Or maybe the explanation does not lie in the peak load.

 Ross H Miller from the Department of Kinesiology at the University of Maryland offers an alternative view (1) and an alternative analysis of the relevant forces conspiring to "wear out" the knees.

He suggested that peak load is not the relevant variable but rather it is the "average load per distance traveled"  which is said to be surprisingly low and purportedly similar to walking.

Ross also discussed the notion of cartilage conditioning .Knee cartilage glycosaminoglycan content( which affects lubrication and shock absorption ) has shown in one study to be greater in recreational runners and even greater in high volume runners.

"... a man hears what he wants to hear and disregards the rest" Paul Simon.The Boxer

1) Miller, RH "Joint loading in runners does not initiate knee osteoarthritis" Exerc Sports Sci  Rev 45(2), 87-95,4 2017

Thursday, March 23, 2017

CRT-non-responders, responders and the rare super responder

About one third of patients with heart failure (HF) do not benefit appreciably or respond to cardiac resynchronization treatment (CRT). Some other have a clinical benefit with physiological confirmation in the form of echocardiographic demonstration of reduction in heart size and increase in the ejection fraction. A relatively small subset show a marked improvement both symptomatically and in terms of impressive  improvement in terms of ejection fraction and reduction in left ventricular size.

Neither EKG nor echocardiographic  patterns accurately predict who will respond and to what degree. However, patients with a LBBB EKG pattern -particularly using the new criteria suggested by Strauss (1 )- are much more likely to have a favorable response.  In fact CRT basically "treats" the electric and associated mechanical dyssynchrony imposed by the left bundle branch block.Some of the variables influencing response include how much myocardial damage may have already occurred in the patient  ( e.g. heart attacks) and the location of the left ventricular lead in relationship to left ventricular scar(s).

The most dramatic example of super responders was reported  by Vaillent et al in 2013. (2). They described 6 patients with a diagnosis of LBBB without evidence of coronary or other heart disease and an EJ of greater than 50% at the time of diagnosis. Over a period of five to 21 years all developed  heart failure severe enough to warrant referral for CRT. Following CRT, ejection fraction improved greatly , five of the six within 3 months .Mean EJ increased from 31 to 56.In one patient , from 26 to 60.Other cardiac functional indices improved as well

The authors suggest that these cases "strongly support the concept of LBBB-induced cardiomyopathy".This idea was apparently suggested earlier by Blanc et al in 2005 (4)

LBBB induced heart failure represents a vary small percentage of patient who are treated with CRT. Ghani et al (3) report on the predictors of long term outcome of "super-responders to CRT which they define as Left ventricular EF (LVEF) greater than 50% ( mean of 54.9%, +/-6) on follow-up echocardiogram.The group whose EF was between 30 and 50% were labelled as "responders"

They describe 56 patients from a group of 347 patients with primary CRT D indication. The predictors were female sex,nonischemic  etiology,higher EF at baseline and wider QRS duration.

Vaillant's patients , when compared to Ghani's patient, perhaps could be considered "super super" responders.

1. Strauss DG et al, Defining Left Bundle Branch block in the Era of Cardiac Resynchronization Therapy. American J Cardiology 2011,Vol 107 pg 927-934

2. Vaillant C et al. Resolution of left bundle branch block induced cardiomyopathy by cardiac resynchronization therapy. J. Amer College of Cardiology 2013,vol 61, p 1089

3. Ghani, S  et al  Predictors and long term outcome of super-responders to cardiac resynchronization therapy. Clin Cardiology 2017

4.Blanc J et al. Evaluation of left bundle branch lock 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

Sunday, March 19, 2017

Do low levels of cardiovascular fitness predispose to cardiac hypertrophy?

 There is evidence  that suggests low levels of cardiac fitness predispose to maladaptive cardiac remodeling  typically manifest as concentric remodeling and concentric hypertrophy and increased ventricular stiffness and diastolic dysfunction.

Lovic and Kokkinos and co workers correctly point out that the cardiac hypertrophy consequent to  high blood ppressure differs from the typical physiological cardiac hypertrophy of the endurance athlete realizing that  extreme examples of the latter can be difficult to distinguish from the former.

Lovic et al  makes the following  argument in a 2016 issue of the Journal of Hypertension.

Low fitness level individuals will reach a systolic blood  pressure of 150 at low levels of exercise, e.g. 4-5 METS , which are  levels commonly encountered in some activities  of everyday living.
150 systolic  blood pressure is necessary to trigger cardaic remodeling. Individuals,who are more fit, are able to do that level of work without that degree of BP rise. So individuals with low fitness may spend considerable  time each day with a BP of sufficient magnitude to trigger hypertrophic changes in  the left ventricle.

Their data (1) found an inverse relationship between exercise capacity, blood pressure response to exercise and  left ventricular mass.Futher they have published data that showed 16 weeks of aerobic training resulted in subjects having  a signficiantly lower blood pressure  level when they  exercised at the every day activity level of 3-5 METS. A reduction in previously elevated left ventricular mass was also shown.

Other data consistent  with this notion comes from a study by Brinker et al ( 2) from Southwestern Medical School in Dallas. They studied subjects aged 42 -67 years of age with stress testing and echocardiography. Those indivduasl in the lowest fitness category ( they divided the group into 3 fitness levels ) had 40 % concentric hypertrohy as well as a 9% prevelance of diatolic dysfunction ( as defined  by the e/a ratio on mitral valve echo flow studies)

Data from the Dallas group and others have outlined the concept of there being two distinct cardiac phenotypes related to the development of both heart failure with reduced ejection fraction (HFrEF) and heart failure with preserved ejection fraction (HFpEF).They are:

1)Subclinical systolic dysfunction (EF may be normal but abnormalities detectable by measurement of global strain with speckle echocardiography)),with eccentric cardiac hypertrophy with increased LV diameter)-the proposed precursor to HFrEF

2)Subclinical diastolic dysfunction with concentric LV hypertrophy; with increased relative wall thickness (RWT) -the proposed precursor to diastolic heart failure (HFpEF)

Increasing data strongly suggest that low fitness levels predispose to the precursors of HFpEF.
Lovic's work suggesting that exercise induced elevated blood pressure in the unfit may be one possible mechanism involved.

1)Lovic, D et al Left ventricular hypertrophy in athletes and hypertensive patients.J Clin Hypertension 2017,

2) Brinker SK et al. An association of Cardiorespiratory Fitness with left ventricular remodeling and diastolic dysfunction. JACC Heart Failure., VOl 2, no 3, 2014, p 238

Wednesday, February 22, 2017

Cardiac remodeling -some old and new theory and some data

Following the 1975 echocardiographic study by Morganroth (1) of endurance athletes and resistance exercise athletes and several cross sectional studies that seemed to validate his work the  "Morganroth's  Hypothesis became  the standard exercise physiology party line.

The story goes like this:

Endurance exercise brings about a volume overload or a preload stimulus to the ventricle that lead to eccentric hypertrophy which is an increase in ventricular cavity size and only slight increase in wall thickness. Resistance exercise brings about a pressure overload or an afterload stimulus which leads to concentric hypertrophy in which there is little change in cavity size but thickening of the ventricular wall.,The 2 types can be defined  by the relative wall thickness (RWT) which is 2 x the posterior wall thickness dived by left ventricular diastolic diameter with  a value greater than 0.42 indicating  concentric hypertrophy.

Skeptics have argued that echo studies have inherent  methodological error  ranges too great   to separate groups whose absolute values are not that far apart and MR is a much more precise method and that cross-sectional studies have limited ability  to sort out group difference that  are due to training  from other causes of individual differences.So what did a longitudinal study with MR imaging show.

A 2011 MRI longitudinal study, Spence et al (2) provided interesting data from which one might conclude that endurance exercise does bring about eccentric hypertrophy but resistance exercise does not increase wall thickness.At least not in the small group of resistance exercisers who worked out three times a week for six months.

It is certainly possible that the six months training program in Spence's study was i not enough to bring about concentric hypertrophy. A more recent  meta analysis supplies data and analysis that indicate that there is a typical pattern for endurance exercisers and a pattern for resistance exercise more or less consistent with Morganroth's hypothesis  and a in- between pattern for those who engage in activity in which there is both significant amount of volume and pressure overload such as rowing and cycling.

 Plium et al (3)analyzed echocardiographic data  on 1451 athletes gathered up from some 59 studies.All subjects were  under the age of forty, older athletes excluded so as to not muddy up the data with the effects of aging on heart function and structure.

 Basically the data conformed with Morganroth's hypothesis. Quoting the author's conclusions;

"Divergent cardiac adaptations do occur in the athletes performing dynamic and static sports..However,the classification as an endurance trained heart or a strength-trained heart is not an absolute and dichotomous concept but rather a relative concept."

So a stereotypical runner will have a different  pattern from a wrestler or body builder  but ventricular volume changes and wall thickening occur in both  to varying degrees with the runner tending to a eccentric hypertrophy-remodeling pattern and the wrestler to a concentric pattern while athletes such as cyclist and rowers demonstrate the most marked changes in ventricular volume and wall thickness. 

More surprisingly and maybe more importantly  is the observation that a sedentary life style may evoke a remodeling pattern  characterized  by concentric changes,no increase in ventricular volumes and a tendency to develop diastolic dysfunction.

This is what was reported by Brinker et al (4) from Southwestern Medical School in Dallas in their study of  cardiac function and structure in 2900 subjects from the Cooper Center Longitudinal Study.The subjects age ranged from 42 to 67 years of age and all were either self referred or physician referred to the clinic  and had a normal stress test.Based on the exercise levels achieved on the stress test four fitness levels were designated.  They found that the lowest fit subjects ( presumably  those with a sedentary lifestyle) had a higher prevalence of concentric remodeling as well as diastolic dysfunction than the fitter subjects. There was a 40% prevalence of concentric hypertrophy and 9 % prevalence of diastolic dysfunction ( defined as an E/A ratio greater than 1) in the lowest fit group versus less than 20 % concentric change and 2% diastolic dysfunction in the most fit group. So it is not an all on none thing and fitness does not seem to immunize against concentric  hypertrophy and diastolic dysfunction but made both less likely.

 Both resistance and endurance training cause cardiac remodeling but there may also   be a "inactivity remodeling", as might occur in a sedentary lifestyle The ventricles remodel  whether  you exercise or have a sedentary lifestyle and Brinker's group suggest that the inactivity remodeling may be a precursor to diastolic heart failure (aka HFpEF) and further suggest that long term exercise might be preventive.

That is a thesis I would like to believe. I would be more convinced if it were not for the fact that while  66% of the low fit group were hypertensive so were  only 38% of the fittest group were hypertensive. You wonder if that might not play a role in the concentric hypertrophy. I discussed other work by the Dallas group (see here) which,IMO, provides better evidence for the idea that long term aerobic exercise can reduce the risk of diastolic heart failure.

1. Morganroth, J et  al. Comparative left ventricular dimensions in trained athletes.Anl Int Med. 1975,82(4), 521-524

2. Spence,A et al .A prospective randomized longitudinal MRI study of left ventricular adaptation to endurance and resistance exercise J of Physioloy 14 nov 2011

3.Pluim,B The Athlete's Heart. A Meta-analysis of cardiac structure and function. Circulation 1999:100: 336

4.Brinker, SK et al. Association of Cardiorespiratory Fitness with Left Ventricular Remodeling and diastolic dysfunction. JACC Heart Failure.Vol 2, no.3, 2014, p238

"Humans are pattern-seeking, story-telling animals and we are quite adept at telling stories about patterns,whether they exist or not" Michael Shermer.

Wednesday, February 01, 2017

Parameters on Utopias-something politicians don't want

Peter Boetke in his new book, "Living Economics" throws out the following:

"Economics put parameters on Utopias".

The more famous quote of Friederich Hayek strikes a related chord:

"The curious task of economics is to demonstrate to men how little they really know about what
they imagine they can design."

So politicians need to be careful to have supportive economists on board for their various utopian plans. They will need some that will be very parsimonious with the parameter placements.Fortunately for the politicians they can  always find a least one PhD economist to argue for  whatever position.

Some parameters might have disabused apologists of belief in  the promised utopia of ACA (aka Obamacare) .The hucksters promoting the plan prior to its passage spoke of saving the country from bankruptcy and increasing access to care and improving quality. So how has that worked out for you?

Professor Gruber has been late in providing some parameters .

Monday, January 30, 2017

The major barrier to third party payers control of medical costs is being dismantled

A major barrier ( I argue the major barrier) to control health care costs by the third party payers has been and still is to a lesser degree medical ethics ; more specifically, the duty of the physician to act as a fiduciary for the patient. At one time not long ago when the physician and patient believed or had determined that test x or treatment y was in the best interests of the patient the physician would be the  advocate for the patient  not an agent or employee of the insurance company whose interest was to deny the tests or treatment.He was not tasked with working in some type of mythical society-physician alliance to conserve collective medical resources acting as the steward of those resources.

Not infrequently the physician's desire to be the advocate of the patient and the insurance company desire to limit costs were in opposition.The patient versus the company with the physician on the side of the patient was the common narrative.

What if the medical ethics were different? What if the physician felt an ethical obligation to conserve the " resources of the collective"? What if the impetus for that ethical transformer seemed to take place from within the medical profession?

Whereas once if the physician did not advocate for his patient he might be ashamed but now according to the new ethic a physician might feel guilty by failing to act  as would "stewards of finite resources".  Victor Fuchs in a commentary in the NEJM carried this  insult to logic to its limit in the following way.

In his closing paragraph, Fuchs tells us that when a physician works in a health care collective in which there is a fixed annual budget the physician resolves the dilemma ( between favoring the individual and the collective) by favoring the cost effective option. This according to Fuchs become "appropriate". So,the cost effective choice is the appropriate choice and also the ethical one. It is ethical in the moral calculus of Kant he claims "because if all physicians act the same way,all patients benefit" .It is hard to find statements any sillier in a major medical journal.

 A  major  barrier demolition  occurred in 2002 with the publication of "The Charter" ( Medical Professional in the New Millennium- A Physician Charter) authored by the ABIM  Foundation , the ACP foundation and a European Foundation of Internists.

A number of forays against the barrier had been made earlier including a multi part series in JAMA in which the author proposed a way to increase quality of care while decreasing cost by a egalitarian-utilitarian, cost effectiveness calculus in which the group benefited while a given individual patient might not.  Notable also was the publication  of "New Rules" by Troyen Brennan and Don Berwick in which they advocated elimination of the traditional doctor patient relationship and moving away from "decentralized individualized decision making".  

In The Charter, three major ethical principles were put forth; patient welfare,patient autonomy and social justice. Previously medical ethics was concerned with the relationship of the physician and the patient.Now the authors of the Charter presumed to define the relationship of the physician and society. Further, the relationship they claimed was that the physician was the steward of society's resources. This colossal, gratuitous assertion represented a sea change the implications of which might not have been immediately apparent. To many it was not apparent that implementation of the third principle was in conflict with the first while a number raised objections  the majority took little notice.The dogs barks and the caravan moves on.

 But all of the above really just relates to the intellectual smokescreen. The real elements that have fee for serve on life support and thereby strike a major victory for third party's payers cost saving and profit  enhancing initiatives are ACA,HITECH and now MACRA.

Tuesday, January 24, 2017

Is the athlete's slow heart rate really due to increased vagal tone as conventional wisdom suggests

An article from three British researchers makes a good case that vagal tone is not the reason for the athlete's bradycardia. in a 2015 commentary in the Journal of Physiology.see footnotes

Traditionally, the slow heart rate of endurance athletes is attributed to increased vagal tone but the authors argue that this increased tone has never been demonstrated at least in part because it is not clear how that could even be measured as the vagus carries both afferent and efferent fibbers. Further experimental blockage of the autonomic nervous system has not lead to mitigation of the bradycardia.

They suggests that the slow heart rate is also not due to SA node fibrosis ( apparently a common explanation for SA node disease) as that also has never been demonstrated. They present evidence that the culprit is remodeling of the ion channels and related molecules in the sinus node-more specifically downregulation of the HCN4 channel  (also  strangely known as the "funny channel") . They reference a number of articles claiming there is remolding of  ion channels in aging and familial bradycardia and pulmonary hypertension.

Endurance exercise is known to cause heart remodeling leading to the features of the so called athletes heart ( so called eccentric hypertrophy). It is also know that cessation of exercise will lead to some degree of "re-remodeling" returning the athletes heart  to some degree of that of the sedentary person. Will a similar reversal happen in he electrical system in endurance athletes who quite exercise? or is this remodeling permanent? Baldesberger  et al published a long term followup  in retired professional cyclists who had stopped training for over thirty years and did report an unimpressive lower heart rate on Holter monitoring in 62 cyclists versus 62 golfers ( 66 +- 9 versus 70 +- 8 but 20% did have a HR less than 40 during the day. versus 6 % in the controls.So is the sinus nodes remodeling to some degree not reversible-these cyclists had not trained for 30 years. (There is more interesting data from this study which is a topic for another blog commentary,here the interest was in the bradycardia not other possible cardiac complications . and it did appear the cyclists had a bit more bradycardia.) 


1) D'Souza, A et al . Cross talk opposing view:Bradycardia in the trained athlete is attributable to a downregulation of a pacemaker channel in the sinus node. Journal of Physiology 593 no. 8 1749-1751,April 2015

2) Francesco, D. The Role of the Funny Current in Pacemaker Activity. Circ. Research 2010;106, 434-446

3) Baldesberger, S et al Sinus Node  disease and arrhythmias in the long term follow-up of former professional cyclists. Eur hear journal 2008 29, 71-78

Saturday, January 14, 2017

The minimum exercise levels of the 2008 guidelines won't prevent heart failure.

The 2008 U.S. exercise guidelines recommend a minimum of 2.5 hours of moderate intensity exercise per week or 1.25 hours of vigorous exercise per  week. This can be expressed as 500 METS Min per week or 8.3 MET hours per week. This minimum value is widely quoted but the panel also said that further gains could be made by increasing those exercise levels to twice that value, i.e 5 hours of moderate or 2.5 hours of vigorous exercise. Moderate intensity was defined as between 3 and 5.9 METS and vigorous as over 6 METS.For example running at a 15 min per mile pace is about 7 METS which would be the lower end of what the panel meant by vigorous.This does not address the problem of relating exercise levels to a person's exercise capacity. For example, to  a person with a 02 max of 60 a fifteen minute mile is very mild exercise while the same pace for someone with a 02 max of  25 the term vigorous is  appropriate.

Cardiovascular disease (CVD) risk reduction has been shown in a number of epidemiological studies for people exercising at those  minimum levels and arguably at even lower levelz. Lee et al (1) showed that running at little as 5 to 10 minutes per day would significantly  reduce CVD mortality.This would make a little running seem very effective  while others (Pandy et al see below) did not show that degree of risk reduction with that low a  level of exercise but the minimal recommended  level will likely reduce CVD risk according to several epidemiologic studies.

Eijsvogels (2) reported that the maximal risk reduction was found at a volume of 41 MET-hrs/week, which is 3-4 times the minimal recommended level.However, only 3.5% of the subjects exercised at that level or above and therefor the confidence interval for  hazard ratio (HR) estimation was wide and not statistically significant. The authors emphasized that they found no evidence of harm or adverse cardiovascular outcomes at this level.

While rather low levels of exercise seem to decease CVD risk, heart failure  risk may require higher levels of exercise. Pandy et al (3) and coworkers from Southwestern Medical School reported that heart failure (HF) risk reduction occurred only at levels higher than the minimum guideline recommended values. "We observed a linear dose response for HF risk with a marked reduction in risk at very high doses of PA (physical activity  ) ( 35% risk reduction in HF risk at 2000 MET-min per week)".. This would be 4 times the minimal recommended value or 10 hours of moderate or 5 hours of vigorous exercise per week.

Schnohr et al (4) reported that their analysis of a data set from the Copenhagen City Heart Study demonstrated a U shaped association between all cause mortality and dose of jogging. A number of other articles cited by Schnohr actually report a inverse relationship  showing no U or J shape. Accepting the thesis of  the existence of a U shape curve, he goes to comment on results from several large studies and speculates where the curve might ascend.The studies found that running  about 35 miles per week was the upper limit of incremental health benefits and "these studies found that a weekly cumulative dose of approximately 30 miles of running per week or 46 miles of walking is approximately the "safe" ( my quotes) upper limit for optimizing long term CV health and life expectancy", So if the curve curves up it does not seem to do so at running volumes in the 30 miles per week range. This volume of running would satisfy the running volume "requirement" sufficient to decrease HF risk. suggested by the work of Pandy.

So the epidemiological data would tend to confirm that the 2008 minimum guidelines would decrease CVD and all cause mortality but not the risk of heart failure which requires at least twice that level of exercise.

Several publications from a group in Dallas (5) provide useful insights regarding the mechanism by which a higher level of exercise would lessen heart failure risk, that is diastolic heart failure. Dr Paul Bhella and group  did extensive physiological studies on four groups of healthy volunteers over the age of 64. Four groups were designated   on the basis of their exercise history for the preceding 25 years. (not a typo) 1) sedentary-no more than one exercise session per week  2) casual exerciser-2-3 session per week 3) "committed" exercisers-4-5 session per week and 4)competitive master level athletes -6-7 session per week and competed regularly.  All had normal systolic function ( as defined by a normal resting ejection fraction) but groups one and two has decreased left ventricular compliance while the committed and competitive groups had left ventricular pressure volume curves and left ventricular masses similar to young healthy controls. ( see here for my  further comments and a few caveats regarding this paper including reference to Tanaka's work that challenges the notion that long term endurance exercise can preserve  ventricular compliance)

Quoting Bhella ". . at least 30 minutes of dynamic exercise per session for 4-5 days per week over a lifetime can  sufficiently prevent most of the decreases in LV compliance and distensibility observed with sedentary aging" So the idea is that sedentary aging leads to stiff left ventricle and life long running may mitigate that process.

 In other words 2.5 hours per week which was the higher level of exercise ( i.e. twice the minimum  recommenced by the 2008 panel) might beneficially reduce the age related increase in ventricular stiffness. It does not take that much exercise per week but you have to put in a lot of weeks remember  Bhella's groups activity levels were for the 25 years before the testing. The authors speak of Lifelong exercise. 

 This exercise level is far below the typical exercise histories that one typically  finds in the cases of athletes with atrial fibrillation or the athletes in whom an abnormal gadolinium uptake was reported and whose cases are  sometimes emphasized in various writers warning the public about the dangers of excessive exercise. 2 to 3 times the  2008 Panel'sminimal recommendation should not be considered excessive.

1)Lee, D  Leisure-time Running Reduces All-cause and cardiovascular mortality risk. JACC 64. 472-481.2014

2) Eijsvogels, T, Exercise at the extremes-The amount of exercise to reduce cardiovascular event
JACC, 67, 316-329, 2016

3)Pandey,A Dose-Response Relationship between PHysical Activit and Risk of Heart Failure.A meta-Analysis, Circulation 2015, 132 1786-1794

 4) Schnohr,P Dose of Jogging and Long term Mortality. JACC, 65, 311-410,2015

 5)Bhella, P Impact of Lifelong Exercise "dose" on left ventricular compliance and Distensibility.
JACC 64, 1257-1267 2014

John VonNeumann " There's no sense in being precise when you don"t even know what your're talking about"


Saturday, January 07, 2017

High school and college football deaths average about 3 per year

A recent report by KL Kucera et al give details on high school and college fatalities related to head and/or spinal injuries .

From 2004 through 2015 there were 28 deaths reported related to head or spinal injuries,24 in high school players and 4 in college. 1.1 million play high school football while there are 75,000 collegiate football players.

Four of the 22 high school players had suffered a concussion in the four weeks  preceding the fatal injury and in three cases the second impact syndrome was implicated .Running backs and linebackers were the two most common positions.The head down-head first position was frequently implicated.

 I wonder what  parents and grand parents of high school footballers think about the ambulances frequently parked off to the side of the playing field.

Friday, January 06, 2017

two studies reassuring endurance athletes re long term heart damage

Two, articles, one from Germany and one from Italy might provide some reassurance to long time endurance athletes worried about too much of a good thing damaging the heart.

Bohn et al from Germany reported  a group  of long term endurance athletes with many years of endurance exercise history whose extensive cardiac evaluation showed nothing to suggest that ARVC is a problem.

Pelliccia and co workers studied 1777 active competitive athletes and described echo findings and concluded their tendency to have somewhat larger left atria represented physiological adaptation which is largely without adverse clinical consequences and found a fib to be uncommon, less than 1% and similar   to that of the general  population. He also concluded that left and right ventricular exercise induced remodeling were basically balanced.This conflicts with some of the work of La Gerche  and Heidbuchel who postulate that the right ventricle is less well designed that is the left ventricle  for endurance exercise and and predisposes it to arrhythmias arising right ventricular  remodeling . But finding a bunch of white swans does not preclude the existence of black ones.

The case control studies  reporting hazard ratios of 4 and five in regard to atrial fibrillation in long time endurance athletes ( and the meta analysis that summed them up with some statistical trappings) just might be vulnerable to selection  bias while these two studies just might be vulnerable to survivor bias.

Can "too much" exercise increase risk of atrial fibrillation in men but not women?

Can "excessive " exercise increase the risk of atrial fibrillation in men but somehow spare women hyper-endurance exercisers from that risk? That seems to be what the data show in a 2016 Meta analysis by Mohanty et al published in the June issue of the Journal of Cardiovascular Electrophysiology . See here.

The really fun thing about meta analyses is the frequency with which one can cite conflicting results from various studies. In  another meta analysis Kwok et al found no association with increasing exercise and risk of AF in either sex.  In spite of these conflicting data sets a quasi consensus seems to be that at some level "too much"  exercise predisposes to atrial fibrillation.- determining the level of too much is another matter.  As in  many biological and medical issues it is easier to get a pretty good idea of the direction of the vector than is  ascertaining the magnitude but  sometimes the direction is in dispute as well.