Milrinone Improves Pulmonary Hemodynamics and Right Ventricular Function in Chronic Pulmonary Hypertension

Background. Right ventricular failure after cardiac transplantation is commonly related to preexisting recipient pulmonary hypertension. This study was designed to investigate the effects of intravenous milrinone on pulmonary hemodynamic indices and right ventricular function in a canine model of monocrotaline pyrrole–induced chronic pulmonary hypertension. Methods. Eight mongrel dogs underwent pulmonary artery catheterization to measure right-sided hemodynamic indices before and 6 weeks after a right atrial injection of monocrotaline pyrrole. Six weeks after injection, all hearts were instrumented with a pulmonary artery flow probe, ultrasonic dimension transducers, and micromanometers. Data were collected at baseline and after milrinone infusion. Results. Six weeks after monocrotaline pyrrole injection, significant increases in the pulmonary artery pressure and pulmonary vascular resistance were observed. Milrinone led to significant increases in right ventricular function as well as significant improvements in pulmonary vascular resistance, pulmonary blood flow, and left ventricular filling. Conclusions. This investigation demonstrates the well-known hemodynamic and inotropic effects of milrinone which, in the setting of monocrotaline pyrrole–induced pulmonary hypertension, were also associated with significant increases in pulmonary blood flow and left ventricular filling.