Is endurance exercise bad for the right ventricle?

For someone who recently finished his 50 th marathon, (with a - modestly put- incredible comeback from a mysterious orthopedic disability) the last thing I wanted to hear about is this article presenting evidence that all that running may be setting me up for a problem with my heart, specifically my right ventricle.

As a non-cardiologist I struggled to try and make sense ( and to try and deny the implications of) the observations made. Here they are:

1.22 patients, endurance athletes, with rhythm problems were referred to Dr. Hein Heidbuchel, a cardiologist in Belgium.
2.In 6 the diagnostic criteria for arrhythmogenic right ventricular dysplasia (ARVD) were met.

(ARVD diagnostic criteria can be found here It is a rare cardiac condition,a cardiomyopathy with fatty degeneration and fibrous replacement of the right ventricular wall, tendency to ventricular tachycardia and often a positive family history.The EKG may show inverted t waves in right sided leads and the so-called epsilon waves.)While rare in the U.S., Apparently this entity is significantly more common in parts of Europe (according to the Wikipedia article on ARVD).

3.In 82% of the 22 the criteria for the diagnosis of ARVD were not met but there was some abnormality showing up on testing-i.e. either the ekg,echo or morphology.The summary did not detail exactly what the findings were.

4.In the 5 who had right ventricle biopsies, none had light microscopy evidence of ARVD.

The authors postulate that the volume overload put greater stresses on the thin-walled right ventricle and might be causing ARVD. On the other ( and more reasonable hand), it has been recognized that a cause of arrhythmia in athletes is ARVD.Since these were athletes referred for rhythm problem it is not surprising that some had findings suggestive of ARVD since that condition seems to be fairly well known as a cause of rhythm problems in athletes,at least in parts of Europe.

There is evidence that in the early hours after a marathon or following a full or half Ironman distance triathlon there may occur elevations of troponin in the range seen in myocardial infarctions and there have been reported echocardiographic changes that could be described as cardiac "fatigue". The changes were those of altered relaxation characteristics and a decreased contractility all of which, along with the elevated troponins returned to normal in 48 hours.I am hoping that all of this is just analogous to the sore leg muscles and raised total CK values that remit in a few days and is of as little consequence. On the other hand, here is a paper that uses rather weak and indirect evidence to argue that long term cycling may be harmful to the heart. Also a recent NYT article quotes another study showing increased troponin levels after a marathon and briefly discussed some other tepid voices of concern that have been raised.

In the late 1970s, a pathologist,Dr. Tom Bassler put forth the overblown thesis that running marathons provided virtual immunity to coronary artery disease. The saga of Jim Fixx and the published data of Dr. Tim Noakes proved that wrong. Maybe some of us keep on running distances that are probably too long to make much sense-and much more than makes sense from a protect-the-heart point of view- still carry some of that bogus notion with as we slog along.