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1 The cardiovascular effects of the beta-adrenoceptor blocking drugs, propranolol and acebutolol, on regional coronary blood flow and left ventricular function have been investigated in the conscious dog with developing myocardial infarction. 2 Propranolol (1 to 1.5 mg/kg) or acebutolol (4 to 5 mg/kg) were administered intravenously 2 to 3 h after occlusion of the left anterior descending coronary artery. 3 Propranolol or acebutolol administration resulted in a relative increase in flow to the ischaemic area of the myocardium, particularly to the subendocardium. 4 Propranolol produced a greater reduction in heart rate and myocardial contractility than acebutolol. 5 These results demonstrate that beta-adrenoceptor blocking drugs reduce myocardial oxygen consumption and increase coronary flow to the ischaemic area of the myocardium after coronary artery occlusion in the conscious dog.

1 The effects of tolamolol on haemodynamics and myocardial contractility were investigated in two groups of six patients undergoing diagnostic cardiac catheterization.2 The intravenous administration of tolamolol (0.15 mg/kg) produced a significant fall in heart rate from a control value (87 +/- 7 to 62 +/- 3 beats/min) 5 min after administration and a concomitant fall in cardiac output from 4.7 +/- 0.9 to 3.5 +/- 0.8 litres/minute. There was no significant change in systemic blood pressure, pulmonary artery blood pressure or stroke volume.3 There was no change in left ventricular end diastolic pressure after tolamolol. There was a fall in the maximum rate of rise of the left ventricular pressure (LV dp/dt(max)) and the derived index of the left ventricular contractile state (V(max)).4 These results suggest that tolamolol has a predominantly negative chronotropic but also a lesser negative inotropic action on the heart.