The issue of the effect(s) of endurance exercise on the right ventricle bothers me from time to time and I have blogged about it before.(see here)
A number of studies have shown that endurance exercise, marathons,triathlons, etc, may result in transient changes in right ventricular function (increased volume , decreased ejection fraction), while such changes in the left ventricle are typically not the case although some transient changes have been documented..But an important question is- do repeated episodes of prolonged exercise lead to some deleterious changes in the right ventricle which could include a predisposition to ventricular tachycardia or worse.Is there an exercise induced clinical picture of ARVD in someone who does not have the recognized genetic profile for ARVD?(see below).After thinking about it again and reading more about it,I think maybe but it does not seem to happen very often.
J. Ector and co workers studied right ventricular (RV) function in a group of 22 endurance athletes who had experienced episodes of ventricular arrhythmias and concluded "Endurance athletes with arrhythmias have a high prevalence of right ventricular structural and/or arrhythmic involvement." ,the implication being the repeated endurance events predisposed to the rhythm problems (Eur Heart J. 2007, Feb 28 (3),345-53)
LaGerche studied 39 endurance athletes, see here, immediately after an endurance event,and one week later with echocardiography and Magnetic resonance Imaging. with gadolinium. Transient RV function changes noted immediately after the event resolved by one week but 5/39 demonstrated late deposition of gadolinium (delayed gadolenium enhancement or DGE) in the interventricular septum.The authors seemed to assume that the MR findings were fibrotic lesions and were causally related to multiple bouts of endurance exercise but the actual cause of the late deposition of gadolinium has not been determined but it is true that in some contexts ( maybe most) the histologic basis of the delayed gadolenium uptake is fibrosis.
Arrhymogenic right ventricular dysplasia (ARVD)-also called Arrhymogenic right ventricular cardiomyopathy) is an inherited condition primarily involving the right ventricle with replacement of cardiac muscle with fibrous tissue and fat, leading to decreased right ventricular function and predisposition to arrhythmias including ventricular tachycardia and ventricular fibrillation.. Typically it is inherited as an autosomal dominant and involves several mutations in the genes that code for the desomsomal adhesive proteins which function to help bind muscle cells together.
ARVC is much more common in Italy and naturally there is more awareness in Italy and more more published research. The most common cause of sudden cardiac death in the young in Italy is ARVC accounting for 22% of deaths versus 7 % from hypertrophic cardiomyopathy (HCM) in contrast to HCM being the most common congenital problem found in sudden deaths in young athletes in the United states.See here for details of the long standing cardiac screening program in Italy.
While it seem reasonable to conjecture that a person with one of the ARVD gene patterns might hasten the clinical manifestations of ARVD by endurance exercise , is it possible/likely that a person could bring about an ARVD-like clinical picture by repeated endurance training and endurance events in the absence of the Italian or other recognized genetic patterns ?
Earlier work in 2009 by Breuckmann et al ( see here ) also demonstrated some marathoners with delayed gadolenium enhancement (DGE) but in a different distribution that seen in LaGerche's subjects. Of 102 marathon runners age 50-72 who had run at least five marathons in the preceding 3 years,12 showed a DGE .Of those, 5 had a "coronary artery disease" pattern along the distribution of the left anterior descending coronary artery while 7 showed a "predominantly midmyocardial patchy pattern".Could these midmyocardial patches of presumed fibrosis be the earliest lesions of a endurance athlete's cardiomyopathy, which to my knowledge, except for arguably ARVC , has not been reported. Have autopsies been done on Tarahumara runners?