Variability of positive inotropic response to acute amrinone administration in chronic cardiac failure

To determine the factors conditioning the variability of positive inotropic response after intravenous acute amrinone administration, 14 patients with chronic cardiac failure were studied by quantitative M-mode and cross-sectional echocardiography. Six patients had idiopathic dilated cardiomyopathy and 8 patients had severe chronic aortic insufficiency. Myocardial contractility (evaluated as peak arterial systolic pressure/end-systolic volume ratio: PAP/ESV) did not change in patients with idiopathic cardiomyopathy, a significant increase of myocardial contractility occurred in patients with aortic regurgitation only if the control value of PAP/ESV was greater than 1. Mean systolic wall stress decreased significantly in all patients, independent of aetiology of cardiac failure and was the factor determining the improvement of left ventricular performance (evaluated as fractional shortening) in patients without changes in myocardial contractility. Maximum improvement in left ventricular performance occurred 10 minutes after amrinone administration. It is concluded that the possibility of detecting the positive inotropic properties of amrinone in man depends on the aetiology of the cardiac failure and on the basal level of myocardial contractility.