AORTIC ATRESIA

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Abstract
Eight cases of aortic atresia are reported and the embryology and haemodynamics of this congenital malformation are discussed. All were newborn infants who died during the 1st week of life. Clinically, they were characterized by dyspnoea, tachycardia, and progressive cyanosis. Anatomically, there was a dilated right atrium with dilatation and hypertrophy of the right ventricle. The pulmonary trunk had a fivefold increase in size, as compared with the ascending aorta. A paradoxically patent foramen ovale was generally noted. An open ductus arteriosus was the rule in all cases. The size of the left atrium was variable. The left ventricular wall was hypertrophied and the cavity was small and pyriform. The ascending aorta up to its ductal segment and the mitral valve were hypoplastic. In 62% of the cases there was gross evidence of venous pulmonary hypertension and pulmonary oedema. The normal embryological events that lead to the formation of the aortic valve are reviewed. The aortic atresia is explained by an excessive growth of the primitive semilunar cusps which adhere by their borders and extremities forming a true diaphragm. The main causative factors are discussed. The hypoplasia is explained as a functional consequence of the atresia. The blood apparently flows from the right heart to the lungs and across the ductus arteriosus to the aorta. The oxygenated blood returns to the left atrium and across a paradoxically patient foramen ovale to the right atrium. The heart practically functions like a cor biloculare with a single atrium filling a single ventricle.