Effect of intravenous and oral pindolol on exercise tolerance and electrocardiographic changes in angina pectoris

The effects of intravenous (0.4 mg) and oral pindolol (5 mg, t.i.d.) on exercise tolerance and electrocardiographic ST-segment changes were investigated in 20 patients with documented coronary artery disease (16 males and 4 females; mean age, 56.7 years). A randomized double-blind crossover design was used, and graded submaximal exercise was performed on a bicycle ergometer. Pindolol significantly decreased heart rate at rest, and during and after exercise. The time intervals before the appearance of ST depression, before anginal pain, and before the cessation of work were significantly increased after beta-adrenergic blockade, and work tolerance was enhanced, both indicating that pindolol is an effective antianginal agent. Angina appeared at a lower heart rate after pindolol. Anginal pain and cessation of work were associated with significantly less ST-segment depression after pindolol, suggesting that the relation between ST depression and myocardial ischemia is altered by beta-adrenergic blockade. The appearance and disappearance of ST-segment changes correlated closely with heart rate during placebo and pindolol treatment. Heart rate thus seems to be a major determinant of ST-segment depression during and after exercise in coronary artery disease.