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Conotruncal defects are a group of congenital heart malformations affecting the outflow tracts of the heart, including tetralogy of Fallot, transposition of great arteries, truncus arteriosus, and double outlet right ventricle. These defects result from abnormal development of the cardiac neural crest cells and conotruncal septation during embryogenesis. They represent approximately 20-30% of all congenital heart diseases and often require surgical intervention in infancy or childhood.
Conotruncal defects arise from disrupted migration and differentiation of cardiac neural crest cells between the 4th and 8th weeks of gestation, leading to abnormal septation of the truncus arteriosus and conus cordis. This results in malformation of the aortic and pulmonary outflow tracts, ventricular septal defects, and abnormal positioning of the great vessels. The underlying mechanisms involve complex genetic factors, including 22q11.2 deletions, and environmental influences that disrupt normal cardiac morphogenesis.
Clinical presentation varies depending on the specific defect but commonly includes cyanosis, exercise intolerance, failure to thrive, and clubbing in cases with right-to-left shunting. Diagnosis relies on echocardiography, cardiac catheterization, and advanced imaging to assess anatomy and hemodynamics. Management typically involves staged surgical repair, with timing and approach dependent on the severity of symptoms, degree of cyanosis, and risk of developing irreversible pulmonary vascular disease.