Does endurance exercise promote life-threatening changes in athletes' hearts?
Some high-level athletes who take part in endurance exercise sports can develop a rare but life-threatening condition called ventricular arrhythmia (VA) in which the heart beats at an abnormal rate and rhythm. Now, a new study has shown that most of the athletes with VA have dysfunctional right ventricles.
The finding adds weight to the hypothesis that endurance sports might contribute to changes in the heart that lead to dysfunction and heart rhythm disturbances, according to the authors of the report published in the European Heart Journal  today (Monday 22 January).
VA is a heart rhythm disturbance that occurs in the ventricles (lower chambers) of the heart. It can be the cause of sudden death in athletes. There are many underlying causes of VA and often it is due to inherited diseases. Previous studies have found that VA in endurance athletes, such as cyclists, runners and kayakers, often originates from the right ventricle (RV), even when there are no previous symptoms that would enable a diagnosis of a condition called arrhythmogenic right ventricular cardiomyopathy (ARVC) to be made, and no family history of ARVC. A family history is usually present in 30-50% of reported cases of ARVC.
Researchers at the University Hospital Gasthuisberg at the University of Leuven in Belgium, set out to study whether abnormalities in the functioning of the RV might be present in endurance athletes with VA.
They studied 22 endurance athletes  who had been referred to them with VA between July 1997 and April 2005. None had abnormal wall thickening of the left ventricle (hypertrophic cardiomyopathy) or coronary abnormalities. They compared them with 15 endurance athletes without VA and a control group of non-athletes without VA. The athletes were Belgian and Dutch men aged between 18 and 55.
Using four methods for quantitative angiography (X-ray of the heart chambers) to study the RV, they measured the volume of blood in the relaxed RV (end-diastolic volume, EDV), the volume of blood left in the RV after the heart had contracted (end-systolic volume, ESV) and the fraction of blood pumped out of the RV in each heart beat (ejection fraction, EF). In addition, they measured the change in the diameter of the part of the RV where the blood flows out to the arteries (RV outflow tract shortening fraction, SF), and the thickness of the ventricular walls.
Hein Heidbьchel, professor of cardiology/electrophysiology and director of the clinical EP laboratory who led the team, explained: "Although arrhythmogenic right ventricular cardiomyopathy is a known cause of arrhythmias in athletes, we found that we could diagnose it unequivocally in only six of the 22 athletes (27%). However, we could assign arrhythmias as definitely or probably originating from the right ventricle in 82% of the patients