Effects of pimobendan (UD-CG 115 BS) on left ventricular inotropic state in conscious dogs and in patients with heart failure.

The purpose of this study was to examine the time course of the changes in left ventricular inotropic state after intravenous pimobendan administration. In conscious dogs, cumulative doses of 1 and 2.5 mg of pimobendan significantly increased heart rate and the isovolumic indices of inotropic state and relaxation. The maximal effect, however, required 2 h to be present. The changes in cardiac index and capillary wedge pressure after the intravenous administration of 5 mg to patients with heart failure confirmed this slightly delayed action of pimobendan. Accordingly, the effects of pimobendan on left ventricular inotropic state in patients with moderate to severe heart failure were determined during cardiac catheterization 130-150 min after injection of 5 (n = 3) or 2.5 (n = 4) mg. After drug administration, heart rate increased slightly (+7 beats/min; NS) while left ventricular end-diastolic and systolic pressure both decreased significantly (from 22.7 to 9.2 mm Hg, p less than 0.007 and from 123 to 90 mm Hg, p less than 0.025, respectively). The isovolumic index of contractility (dP/dt)/DP40 increased by 19.6 +/- 14.7% (p less than 0.02) and the slope of the late systolic stress-volume relationship improved by 48% (p less than 0.05). It is concluded that pimobendan is a positive inotropic agent in the failing human heart as well as a powerful veno- and arteriodilator.