truncus arteriosus
Summary
Truncus arteriosus is a rare congenital heart defect where a single large vessel arises from the heart and gives rise to the systemic, coronary, and pulmonary circulations. It represents failure of the truncus arteriosus to separate into distinct aorta and pulmonary artery during embryonic development, always associated with a ventricular septal defect.
Detail
Truncus arteriosus occurs due to failure of the conotruncal ridges to spiral and divide the embryonic truncus arteriosus into separate aortic and pulmonary outflow tracts during weeks 5-8 of gestation. The single large vessel overrides both ventricles through an obligatory large ventricular septal defect. Blood from both ventricles mixes in the common trunk, leading to volume overload of both ventricles and pulmonary overcirculation. Patients present with early cyanosis, congestive heart failure, and failure to thrive in infancy. Without surgical intervention, most patients develop irreversible pulmonary vascular disease (Eisenmenger syndrome) by age 2. The defect is classified into Types I-IV based on the origin of pulmonary arteries from the common trunk. Associated anomalies include interrupted aortic arch (10-15%), right aortic arch (30%), and DiGeorge syndrome (22q11.2 deletion). Diagnosis is confirmed by echocardiography showing the single vessel arising from the heart. Treatment requires early complete surgical repair (Rastelli operation) typically performed within the first year of life to prevent irreversible pulmonary hypertension.
Sources
- Lilly's Pathophysiology of Heart Disease
- Moss and Adams' Heart Disease in Infants, Children, and Adolescents
- First Aid for the USMLE Step 1
- American Heart Association Scientific Statements on Congenital Heart Disease
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