Acute effects of a single low oral dose of pimobendan on left ventricular systolic and diastolic function in patients with congestive heart failure

A recent long-term multicenter trial has shown that pimobendan is more effe ctive when administered in low doses. However, no data are available concer ning the effect of a low dose of pimobendan on the systolic and diastolic p ressure-volume relations in patients with heart failure. Therefore we exami ned the effects of a single low dose of oral pimobendan, a calcium sensitiz er, on systolic and diastolic hemodynamics in patients with cardiomyopathy and congestive heart failure. We measured the left ventricular (LV) pressur e-volume relations using a conductance catheter with a micromanometer tip i n 10 patients with chronic congestive heart failure resulting from idiopath ic cardiomyopathy before and 45 and 90 min after administration of a single oral dose of 2.5 mg of pimobendan. End-systolic elastance was used as an i ndex of LV contractility and was measured during transient occlusion of the inferior vena cava. End-systolic elastance increased significantly by 25% at 45 min (p < 0.05) and by 55% at 90 min (p < 0.01) without an increase in myocardial oxygen consumption. The inotropic effect was accompanied by imp roved ventriculoarterial coupling. This effect was attenuated in patients w ith severely impaired myocardial contractility. LV relaxation, assessed by the time constant of isovolumic pressure decay (T-1/2), was significantly s hortened at 90 min (from 47.7 +/- 1.9 to 41.2 +/- 1.7 ms; p < 0.01), althou gh it remained unchanged at 45 min. The diastolic pressure-volume relation showed a leftward and downward shift in all patients. These results indicat e that low-dose oral pimobendan had favorable short-term inotropic and lusi tropic effects in patients with congestive heart failure caused by idiopath ic dilated cardiomyopathy, and may thus be a useful alternative to traditio nal agents. Further study in a large-scale trial is merited.