Exercise-induced ventricular arrhythmias in patients with healed myocardial infarction

Controversy exists about the clinical and prognostic significance of exercise-induced ventricular arrhythmias late after myocardial infarction. The aim of the study was to identify the main clinical and prognostic features of exercise-induced ventricular arrhythmias in out-patients with healed Q-wave myocardial infarction.

The study population was 777 consecutive patients who underwent a symptom-limited (Bruce protocol) treadmill test from May 1988 to January 1991 after myocardial infarction (at least 1 year). Clinical and exercise data were prospectively entered in a computerized database and retrospectively two different groups were selected: (1) 228 patients with exercise-induced ventricular arrhythmias; (2) 549 patients without. Incidence and morphology of exercise-induced ventricular arrhythmias, various exercise parameters and a follow-up were evaluated.

Patients with exercise-induced ventricular arrhythmias were older (P < 0.001), had higher blood pressure (P < 0.03) and peak exercise rate pressure product (P < 0.00) than the others. No difference was found in the incidence of exercise-ischaemia: either symptomatic or not. When simple (< or = 2 Lown) versus complex (> or = 3 Lown) exercise-induced ventricular arrhythmias were considered, the latter were more frequent in patients with anterior myocardial infarction, shorter exercise duration (P < 0.001) and lower exercise rate pressure product, lower ejection fraction and lower incidence of exercise-induced ischaemia. In the follow-up (mean 24 +/- 13 month) there were 24 deaths: five (2.2%) in patients with exercise-induced ventricular arrhythmias and 19 (3.4%) in patients without. Cardiac event rate was similar in both groups.

We conclude that in out-patients with healed myocardial infarction exercise-induced ventricular arrhythmias are quite frequent, but they are not associated with exercise-induced ischaemia, either symptomatic or not. Exercise-induced ventricular arrhythmias seem to be related to age or peak workload. Moreover patients with these arrhythmias have no adjunctive negative risk on prognosis.