Reversal of depressant effects of propranolol on the left ventricular pump function by nifedipine in dogs with chronic ischaemia.

Abstract

The aim of this study was to clarify the combined effects of propranolol and nifedipine on the regional wall motion and haemodynamic variables of the heart in dogs with chronic ischaemia. After an injection of propranolol the heart rate and stroke volume significantly decreased (from 128(18) beats X min-1 to 113(12) beats X min-1 and from 15.1(3.1) ml to 12.2(2.6) ml respectively) and the left ventricular end diastolic pressure and systemic vascular resistance in systole increased significantly (from 7.3(1.5) mmHg to 10.0(1.8) mmHg and from 8.61(1.42) kPa X litre-1 X min-1 to 11.80(1.59) kPa X litre-1 X min-1 respectively). In the regional myocardium the end diastolic length increased significantly in both border and normal zones (7(3)% and 4(2)% respectively) and the percentage systolic shortening in the normal zone decreased significantly from 18.0(3.1)% to 15.1(2.9)%. In the border and infarcted zones the percentage systolic shortening or systolic lengthening did not change. The administration of nifedipine resulted in significant decreases in left ventricular systolic pressure and in systemic vascular resistance (from 122(17) mmHg to 105(14) mmHg and from 11.80(1.59) kPa X litre-1 X min-1 to 6.63(1.24) kPa X litre-1 X min-1 respectively) and stroke volume increased to 18.2(4.4) ml. The percentage systolic shortening in the border and normal zones improved significantly to 9.8(3.2)% and 19.2(3.7)% respectively without any change in end diastolic length and left ventricular end diastolic pressure. In the infarcted zone no significant change in systolic lengthening or end diastolic length was seen. Thus impaired left ventricular pump function induced by propranolol was reversed by nifedipine.