Effect of quinapril or metoprolol on heart rate variability in post-myocardial infarction patients

The effect of quinapril or metoprolol on heart rate variability (HRV) indexes was studied in patients who had recovered from acute myocardial infarction. Patients with stable coronary artery disease and normal volunteers were used as controls. Sixty patients with uncomplicated myocardial infarction (aged 32 to 74 years [mean 56.7]) were randomized to quinapril (n = 25), metoprolol (n = 25), and placebo (n = 10). HRV was assessed 5 days (baseline) and 35 days after the onset of acute myocardial infarction. After the baseline studies, the post-myocardial infarction patients were treated with metoprolol (50 to 100 mg/day), quinapril (5 to 10 mg/day), or placebo. Twenty patients with stable coronary artery disease and 20 healthy volunteers, age- and sex-matched to myocardial infarction patients, were used as controls. Compared with placebo, quinapril and metoprolol increased HRV indexes significantly 35 days after the onset of myocardial infarction. HRV indexes were not statistically different between the 2 treatment groups. At baseline and after therapy, HRV was similar in patients with anterior or inferior wall myocardial infarction. HRV 35 days after the onset of myocardial infarction was not different from HRV in patients with stable coronary artery disease, but was decreased when compared with that in normal volunteers. Data suggest that quinapril has the same beneficial effect on HRV indexes as metoprolol in patients who have recovered from uncomplicated acute myocardial infarction.