On the cardiovascular and antiarrhythmic actions of the cardioselective beta‐adrenoceptor antagonist bevantolol in the pig

The cardioselective beta‐adrenoceptor antagonist bevantolol (1‐[(3,4‐dimethoxyphenethyl)amino]‐3‐(m‐tolyloxy)‐2‐propanol monohydrochloride) was studied for its effects on cardiac performance and on coronary artery occlusion‐induced ventricular fibrillation in anesthetized open‐chest pigs. In doses of 0.5‐‐3.0 mg·kg −1 the drug caused dose‐dependent decreases in cardiac output (10‐‐35%) that were primarily due to a negative chronotropic action, as heart rate decreased considerably more (10‐‐25%) than stroke volume (0‐‐15%). The decrease in stroke volume appeared to be due to a decrease in maxLVdP/dt (up to 40%) and a mild vasoconstriction (≥20%) of the systemic arterial vascular bed. Myocardial blood flow (25‐‐45%) and O 2 extraction both decreased, but cerebral blood flow was well preserved. Decreases in perfusion of some organs (kidneys, liver, and stomach) were similar to those in cardiac output, but that of the small intestine was not significantly affected. After ligation of the left anterior descending coronary artery at its midpoint, bevantolol prevented ventricular fibrillation during the earliest phase of ectopic activity, but was ineffective during the second phase of the early arrhythmias.