Pulmonary Vascular Disease in Patients with Fontan-Type Circulation

Abstract

Functionally univentricular hearts represent 3–5% of all congenital heart diseases, including patient post-surgical palliation with a Fontan-type circulation. In this situation, the only functional ventricle is used to sustain systemic output. Consequently, there is no sub-pulmonary ventricle, and pulmonary blood flow is mainly passive and dependent of elevated systemic venous pressure and negative intrathoracic pressure during inspiration as the driving forces. A low pulmonary vascular resistance is crucial for the optimal functioning of the Fontan circulation. However, pulmonary vascular resistance may be elevated due to neonatal cyanosis as well as pulmonary hyper- or hypo-perfusion. Furthermore, non-pulsatile pulmonary blood flow among other factors in the Fontan-type circulation may cause an increase in pulmonary vascular resistance over time. Modulation of pulmonary blood flow is challenging. Conventional heart failure therapy fails to improve cardiac output in most Fontan patients, whereas direct modulation of pulmonary vascular resistance by the three different pathways of prostacyclin, nitric oxide and endothelin pathway may improve haemodynamics to some extent.