Nitric oxide improves pulmonary vascular impedance, transpulmonary efficiency, and left ventricular filling in chronic pulmonary hypertension

Abstract

Objective: Chronic pulmonary hypertension is difficult to treat and despite the introduction of several therapeutic options, no single therapy is universally recommended. Nitric oxide has had some role clinically in improving pulmonary hemodynamics in this setting; however, basic investigation has not been performed in an appropriate large animal model of stable pulmonary hypertension. This study was designed to examine the effects of inhaled nitric oxide on pulmonary hemodynamics in the setting of a canine model of monocrotaline pyrrole–induced chronic pulmonary hypertension and used Fourier analysis for assessment of pulmonary vascular impedance. Methods: Sixteen mongrel dogs (22 to 25 kg) were used. Animals underwent percutaneous pulmonary artery catheterization to measure right-sided hemodynamics before and 6 weeks after a right atrial injection of either monocrotaline pyrrole ( n = 8) or placebo ( n = 8). Six weeks after the injection all hearts were instrumented with an ultrasonic flow probe, sonomicrometric dimension transducers, and micromanometers. Data were collected at baseline and after nitric oxide administration. Harmonic derivation of functional data was achieved with Fourier analysis. Results: Six weeks after the injection, significant increases in pulmonary artery pressure and pulmonary vascular resistance were observed in the monocrotaline pyrrole group. Nitric oxide led to significant decreases in pulmonary vascular impedance. Significant improvements in pulmonary blood flow, transpulmonary efficiency, and left ventricular filling were also observed. Conclusions: This investigation demonstrates the well-known clinical effects of nitric oxide in improving pulmonary hypertension, which were also associated with an increase in pulmonary blood flow, transpulmonary efficiency, and left ventricular filling in the setting of monocrotaline pyrrole–induced pulmonary hypertension. (J Thorac Cardiovasc Surg 1997;113:849-57)