A Comparison of the Effects of β-Blockers With and Without Intrinsic Sympathomimetic Activity on Hemodynamics and Left Ventricular Function at Rest and During Exercise in Patients with Coronary Artery Disease

Abstract

The effects on hemodynamics and left ventricular function of propranolol and pindolol, .beta.-blockers without and with intrinsic sympathomimetic activity (ISA), respectively, were compared in six men with stable exertional angina at rest and during symptom-limited bicycle exercise. The study was controlled and double blinded, and the order of drug administration was randomized. The dosage of each drug (propranolol 0.15 mg/kg i.v., pindolol 0.02 mg/kg i.v.) was chosen to reduce exercise tachycardia by approximately 18%. Exercise capacity and duration were similar after each drug, and both drugs similarly reduced ST depression during exercise. At rest, propranolol significantly reduced heart rate, systolic arterial pressure, rate-pressure product, stroke volume index, cardiac index, and left ventricular ejection fraction, and increased systemic vascular resistance. In contrast, pindolol significantly reduced only the rate pressure product and cardiac index, and to a lesser extent than propranolol. During exercise on the other hand, both drugs reduced the heart rate, arterial pressure, rate-pressure product, and cardiac index to a similar degree. Neither drug altered pulmonary artery wedge pressure, systemic vascular resistance, stroke volume index, left ventricular ejection fraction, or left ventricular end-diastolic and end-systolic volume indices. At equipotent .beta.-blocking dosages, ISA in pindolol reduced the effects of .beta.-blockade on resting hemodynamics and left ventricular function compared to propranolol, but during exercise the influence of ISA was reduced; and both pindolol and propranolol exert similar effects on hemodynamics and left ventricular function.