Signal averaged electrocardiogram after exercise in patients with mitral valve prolapse

While late potentials are correlated with an increased incidence of ventricular tachycardia, they are not necessarily a good predictor of ventricular electrical instability in patients with mitral valve prolapse (MVP). Our objective was to determine whether the signal averaged electrocardiogram (SAECG) after exercise can discriminate groups with a higher frequency of ventricular arrhythmia from those without. The SAECG was recorded before and after treadmill exercise in 20 normal subjects (N group), 20 patients with MVP (MVP group) and 10 patients with old myocardial infarction (MI group). Five patients (25%) in the MVP group and two patients (33%) in the MI group had late potentials before exercise. Late potentials in the MI group did not disappear with exercise, whereas they disappeared with exercise in two patients in the MVP group. The results suggest that the late potentials observed in patients with MVP differ in nature from those with old myocardial infarction and are not always related to lethal arrhythmia.