Increased dispersion of ventricular repolarization during recovery from exercise

In a recent study, frequent ectopy during recovery from exercise was reported to bear an increased risk for death, whereas frequent ectopy during exercise did not. We compared exercise- and recovery ECGs to corroborate the hypothesis that dispersion of ventricular repolarization is augmented during recovery. In healthy male subjects spanning a large range of fitness, we analyzed all 10-s ECGs recorded during maximal oxygen consumption tests. We selected for every recovery ECG the best heart rate-matched exercise ECG in the same subject, and compared several ECG parameters between the matched ECGs. The observed recovery-exercise differences in these parameters indicate that dispersion of ventricular repolarization increases early during recovery, particularly due to increased action potential duration heterogeneity. Increased vagal tone during recovery may be the cause of this potential threat, apparently most outspoken in highly fit subjects