Patients with vascular anomalies who have coexisting heart disease and shunt connections in the systemic or pulmonary circulation are at high risk for cardiopulmonary complications or hemodynamic decompensation of their fast-flow vascular anomaly.
An example of a left-to-right shunt defect is the persistent ductus arteriosus, which can lead to pressure and volume stress on the heart. Cardiac disease with right-to-left shunt causes increased cyanosis in affected patients. An important cause of a right-to-left shunt is a patent foramen ovale. Pathophysiologically, there is a significant decrease in flow resistance in the pulmonary circulation, as found in arteriovenous fistulas between the pulmonary artery and pulmonary vein. Approximately 70% of all fistulas between the pulmonary artery and pulmonary vein are associated with hereditary hemorrhagic teleangiectasia (HHT) and may result in chronic cardiac insufficiency if left untreated.