Effects of amrinone on the right side of the heart.

Unlike the left ventricle, the right ventricle is a thin-walled, low-pressure, volume-displacement pump that ensures adequacy of left ventricular filling and maintains a low pressure in the venous system. In healthy human subjects, there is no burden for right ventricular systolic emptying, because normal pulmonary vessels have a low impedance and show a passive recruitment when cardiac output increases. However, under a pathological condition like right-sided heart failure, the right ventricle may exert profound influences on the circulatory state. Right-sided heart failure most often results from primary or secondary pulmonary arterial hypertension. Pharmacologic vasodilation of the hypertensive pulmonary vascular bed is an ideal therapy for right-sided heart failure. The bipyridine derivative amrinone has positive inotropic and direct vasodilator properties, and therefore seems suitable for the therapy of right ventricular dysfunction accompanied by pulmonary arterial hypertension. In one study, 12 patients with right ventricular failure due to mitral valve stenosis were evaluated, and it was found that amrinone increased cardiac output by 25% and decreased pulmonary artery pressure by 30% to 50%. In a second study, the hemodynamic properties of amrinone versus sodium nitroprusside were compared in patients with aortic or mitral valve failure (n = 17), when both agents lowered systemic vascular resistance equally. Pulmonary vascular resistance decreased significantly (25%) only in the amrinone group.