Antianginal and haemodynamic effects of alpha 1-adrenoceptor blockade.

We studied the effects of alpha 1-adrenoceptor blockade with indoramin on exercise tolerance in 15 patients with chronic stable angina using a double-blind crossover protocol. Thirteen patients had been receiving beta-adrenoceptor blocking drugs and nitrates. The therapy of these patients was continued unchanged throughout the study. Indoramin, in a dose of 25 mg three times daily, prolonged exercise duration by 17% (p less than 0.01) and increased oxygen consumption during exercise by 21% (p less than 0.01), while the maximal double product was unchanged. This increase in exercise capacity was associated with significant attenuation in ST segment depression during exercise. To investigate the mechanism of this antianginal effect, we studied the effects of indoramin (0.2 mg/kg i.v.) on coronary and systemic haemodynamics in a further 11 male patients with chronic stable angina who were receiving beta-adrenoceptor blocking drugs. Measurements were obtained during sinus rhythm and during atrial pacing from 100 beats/min, incremented by 20 beats/min at intervals of 3 min until the onset of angina. Indoramin had no effect on resting heart rate (64 +/- 2 vs. 67 +/- 2 beats/min), but did prolong pacing time to angina (7.4 +/- 0.7 vs. 5.4 +/- 0.5 min; p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)