Effects of pimobendan on hemodynamics and myocardial energetics in patients with idiopathic dilated cardiomyopathy: comparison with nitroprusside.

The influence of pimobendan and nitroprusside on hemodynamics was investigated in nine patients with idiopathic dilated cardiomyopathy (NYHA class II-III). Pimobendan and nitroprusside resulted in a comparable decrease of left ventricular end-diastolic wall stress (preload) by 46% (p less than 0.01) and 52% (p less than 0.01), respectively, and of end-systolic wall stress (afterload) by 36% (p less than 0.01) and 34% (p less than 0.01), respectively. Cardiac index increased from 3.2 +/- 0.4 to 4.2 +/- 0.8 L/min/m2 with pimobendan (p less than 0.01) and did not significantly change with nitroprusside (3.0 +/- 0.6 L/min/m2). Compared to nitroprusside, pimobendan resulted in a significant increase in stroke volume index by 37% (p less than 0.01) and maximum rate of left ventricular pressure rise by 23% (p less than 0.05). Heart rate did not significantly change with either drug. Following the application of pimobendan, there was a decrease in myocardial oxygen consumption from 14.3 +/- 5.1 to 10.6 +/- 3.8 ml/min/100 g (p less than 0.05). The ratio of myocardial oxygen consumption and systolic stress-time integral did not significantly change. Thus, in comparison with nitroprusside, pimobendan exhibits significant inotropic and vasodilating properties. The hemodynamic actions of pimobendan are associated with favorable effects on myocardial energetics.