Truncus arteriosus is a rare congenital heart defect in which a single large arterial trunk (vessel) arises from the heart instead of the two separate vessels (aorta and pulmonary artery) that are normally present. Blood from both the right and left ventricles, which communicate through a large ventricular septal defect (VSD), flows into this common trunk. The single vessel then gives rise to both the systemic and pulmonary circulations.
Because oxygenated and deoxygenated blood mix, and because pulmonary blood flow is largely unregulated, truncus arteriosus leads to cyanosis (low oxygen in the blood) and, if left untreated, early development of pulmonary hypertension due to excessive pulmonary blood flow. It is a critical congenital heart defect requiring surgical repair in the neonatal period.
Surgical correction involves separating the pulmonary arteries from the common trunk, closing the VSD, and creating a connection between the right ventricle and the pulmonary arteries (using a conduit or homograft). Because the conduit cannot grow with the child, re-operations are expected as the patient grows. Long-term follow-up in Adult Congenital Heart Disease (ACHD) services is required, with monitoring for arrhythmia, conduit failure, and ventricular dysfunction, all of which can increase the risk of adverse events including sudden cardiac arrest.
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