Hemodynamics and arteriovenous malformations in cavopulmonary anastomosis: The case for residual antegrade pulsatile flow

Abstract

Continuous flow in Fontan circulation results in impairment of pulmonary artery endothelial function, increased pulmonary vascular resistance, and, potentially, late failure of Fontan circulation. Bidirectional cavopulmonary shunt is the interim procedure in palliation of patients with single-ventricle physiology, but pulmonary arteriovenous malformations occur in many patients. In a porcine chronic model of cavopulmonary shunt, we studied pulmonary hemodynamics, pulmonary arteriovenous malformation occurrence, and gas exchange capabilities. We hypothesized that residual antegrade pulsatile pulmonary flow may attenuate the deleterious effects of nonpulsatile Fontan-type circulation. Thirty pigs underwent a sham procedure (n=10, group I), a cavopulmonary shunt with right pulmonary artery ligation (n=10, group II, nonpulsatile), or a cavopulmonary shunt with proximal right pulmonary artery partial ligation (n=10, group III, micropulsatile). Three months later, invivo hemodynamics, blood gas exchange, pulmonary arteriovenous malformation occurrence, and lung histology were assessed. At 3 months, group II right lungs demonstrated significantly increased pulmonary artery pressure, pulmonary vascular resistance, and evidence of pulmonary arteriovenous malformations compared with groups I and III (all P<.001). Group III lungs also showed increased pulmonary artery pressure and pulmonary vascular resistance compared with the sham group, but significantly less than group II. Group III right lungs had the best gas exchange performance, with less histologic changes compared with group II. We developed a viable chronic large animal model of bidirectional cavopulmonary anastomosis. Residual antegrade pulsatile flow in the setting of a cavopulmonary shunt prevents pulmonary arteriovenous malformation formation and attenuates, but does not suppress, the development of pulmonary hypertension. From a clinical standpoint, these data would support keeping a small amount of antegrade pulsatile flow during creation of a cavopulmonary shunt.