BACKGROUND: Electrocardiographic abnormalities and premature ventricular 
contractions are common in athletes and are generally benign. However, the 
specific outcome of high-level endurance athletes with frequent and complex 
ventricular arrhythmias is unclear. Also, information on the predictive accuracy 
of different investigations in this subgroup is unknown.
RESULTS: We report on 46 high-level endurance athletes with ventricular 
arrhythmias (45 male; median age 31 years) followed-up for a median of 4.7 
years. Eighty percent were cyclists. Hypertrophic cardiomyopathy or coronary 
abnormalities were present in < or =5%. Eighty percent of the arrhythmias had a 
left bundle branch morphology. Right ventricular (RV) arrhythmogenic involvement 
(based on a combination of multiple criteria) was manifest in 59% of the 
athletes, and suggestive in another 30%. Eighteen athletes developed a major 
arrhythmic event (sudden death in nine, all cyclists). They were significantly 
younger than those without event (median 23 years vs 38 years; P=0.01). Outcome 
could not be predicted by presenting symptoms, non-invasive arrhythmia 
evaluation or morphological findings at baseline. Only the induction of 
sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) during 
invasive electrophysiological testing was significantly related to outcome (RR 
3.4; P=0.02). Focal arrhythmias were associated with a better prognosis than 
those due to reentry (P=0.02) but the mechanism could be determined in only 22 
(48%).
CONCLUSIONS: Complex ventricular arrhythmias do not necessarily represent a 
benign finding in endurance athletes. An electrophysiological study is indicated 
for risk evaluation, both by defining inducibility and identifying the 
arrhythmogenic mechanism. Endurance athletes with arrhythmias have a high 
prevalence of right ventricular structural and/or arrhythmic involvement. 
Endurance sports seems to be related to the development and/or progression of 
the underlying arrhythmogenic substrate.