Beta-blockade in ischaemic heart disease--influence of concomitant ISA or alpha-blockade on haemodynamic profile.Postgrad Med J. 1983; 59 Suppl 3:45-52.PM
To test the hypothesis that the depression of cardiac performance induced by competitive blockade of sympathetic stimulation at beta-adrenoceptors could be attenuated by the addition of a high level of intrinsic sympathomimetic activity (ISA) or concomitant alpha- and beta-blockade, the haemodynamic dose-response effects of propranolol (non-cardioselective, no ISA), pindolol (non-cardioselective, high ISA) and labetalol (non-cardioselective, alpha-blocker) were compared in a randomized study of 30 patients with stable coronary artery disease. Following 4 intravenous (i.v.) doses of each drug given according to a logarithmic cumulative dosage schedule, changes in circulatory variables were measured 2-4 min following each i.v. bolus and during bicycle exercise following the maximum dose of each drug. At rest propranolol induced dose-related reductions in heart rate, cardiac output and increases in pulmonary artery occluded pressure and systemic vascular resistance. The only change in resting haemodynamic variables following pindolol was a small dose-related increase in pulmonary artery occluded pressure. Labetalol induced dose-related falls in systemic blood pressure and vascular resistance with linear increase in cardiac output and pulmonary artery occluded pressure. During exercise the depression of cardiac output and increase in pulmonary artery occluded pressure which occurred in patients randomized to propranolol was effectively attenuated in the pindolol and labetalol groups. These observations on cardiac performance following beta-blockade in ischaemic heart disease suggest a rational basis for the use of compounds with added vasodilator or intrinsic sympathomimetic properties.