Impact of physical deconditioning on ventricular tachyarrhythmias in trained athletes.

Objectives: The purpose of this research was to evaluate the impact of athletic training and, in particular, physical deconditioning, on frequent and/or complex ventricular tachyarrhythmias assessed by 24-h ambulatory (Holter) electrocardiogram (ECG).
Background: Sudden deaths in athletes are usually mediated by ventricular tachyarrhythmias.
Methods: Twenty-four hour ambulatory ECGs were recorded at peak training and after a deconditioning period of 19 +/- 6 weeks (range, 12 to 24 weeks) in a population of 70 trained athletes selected on the basis of frequent and/or complex ventricular tachyarrhythmias (i.e., > or =2,000 premature ventricular depolarization [PVD] and/or > or =1 burst of non-sustained ventricular tachycardia [NSVT]/24 h).
Results: A significant decrease in the frequency and complexity of ventricular arrhythmias was evident after deconditioning: PVDs/24 h: 10,611 +/- 10,078 to 2,165 +/- 4,877 (80% reduction; p < 0.001) and NSVT/24 h: 6 +/- 22 to 0.5 +/- 2, (90% reduction; p = 0.04). In 50 of the 70 athletes (71%), ventricular arrhythmias decreased substantially after detraining (to <500 PVDs/24 h and no NSVT). Most of these athletes with reduced arrhythmias did not have structural cardiovascular abnormalities (37 of 50; 74%). Over the 8 +/- 4-year follow-up period, each of the 70 athletes survived without cardiac symptoms.
Conclusions: Frequent and/or complex ventricular tachyarrhythmias in trained athletes (with and without cardiovascular abnormalities) are sensitive to brief periods of deconditioning. In athletes with heart disease, the resolution of such arrhythmias with detraining may represent a mechanism by which risk for sudden death is reduced. Conversely, in athletes without cardiovascular abnormalities, reduction in frequency of ventricular tachyarrhythmias and the absence of cardiac events in the follow-up support the benign clinical nature of these rhythm disturbances as another expression of athlete's heart.