We sought to identify and characterize the abnormal vascular structures responsible for pulmonary arteriovenous shunting following the Glenn cavopulmonary shunt. Superior cavopulmonary shunt is commonly performed as part of the staged pathway to total cavopulmonary shunt to treat univentricular forms of congenital heart disease, however, clinically significant pulmonary arteriovenous malformations develop in some patients after the procedure. The causes of pulmonary arteriovenous malformations and other pulmonary vascular changes that occur after cavopulmonary shunt are not known. Using a juvenile lamb model of superior cavopulmonary anastomosis that reliably produces pulmonary arteriovenous malformations, we performed echocardiography and morphological analyses to determine the anatomic site of shunting and to identify the vascular structures involved. Pulmonary arteriovenous shunting was identified by contrast echocardiography in all surviving animals (n = 40) following superior cavopulmonary anastomosis. Pulmonary vascular corrosion casts revealed abnormal tortuous vessels joining pulmonary arteries and veins in cavopulmonary shunt animals but not control animals. In conclusion, unusual channels that bridged pulmonary arteries and veins were identified. These may represent the vascular structures responsible NIH Public Access
KeywordsHeart defects; Congenital pulmonary circulation; Arteriovenous malformationThe classic Glenn surgical superior cavopulmonary anastomosis (CPA) is commonly performed as part of the staged Fontan pathway to treat univentricular forms of congenital heart disease [6,7]. Up to 60% of these patients develop pulmonary arteriovenous shunting (PAVS), which may lead to progressive and clinically significant hypoxia [1][2][3]11]. Although PAVS is believed to occur via pulmonary arteriovenous malformations (PAVMs) that develop following creation of a Glenn shunt, the vascular structures responsible for PAVS have not been clearly characterized. It is commonly believed that PAVMs develop because of the absence of a putative hepatic venous 'factor' in the pulmonary circulation of these patients [9,15,17]. Identification and morphologic analysis of the structural components responsible for PAVMs may provide a better understanding of abnormal vascular developmental processes in these patients and facilitate isolation of putative circulating etiological substances. Using a juvenile lamb model that reliably produces pulmonary arteriovenous malformations, we performed echocardiographic, angiographic, and morphologic analyses to identify and characterize the vascular structures involved in PAVS following the Glenn shunt.
Materials and MethodsThese studies were performed in compliance with animal welfare regulations of the University of California-San Francisco and USDA guidelines. Furthermore, these studies conformed to the "Position of the American Heart Association on Research Animal Use," adopted by the American Heart Association on November 11, 1984, and were approved by the University o...