Prenatal Diagnosis of Congenital Absence of Aortic Valve: A Report of Two Cases with Different Outcomes and a Literature Review.

Congenital absence of aortic valve (AAV) is a rare cardiac anomaly associated with high mortality. We present 2 prenatally diagnosed cases of AAV. In both cases, fetal echocardiography showed no aortic valve tissue and free aortic regurgitation. At 24 weeks' gestation, case 1 showed a hypoplastic hypocontractile left ventricle and mitral atresia, but did not develop hydrops and was born at term. Bilateral pulmonary arterial banding was performed with continuous infusion of prostaglandin E1 at 5 days of age followed by Norwood and bidirectional Glenn procedures at 3 months of age. The hypoplastic non-compliant left ventricle and mitral atresia might have limited aortic regurgitation. Case 2 showed hydrops at 23 weeks' gestation. An enlarged hypocontractile left ventricle and massive mitral insufficiency were noted. The regurgitant flow was directed to the right atrium through a foramen ovale. This peculiar hemodynamic established a malignant circuit which was arbitrarily called 'inverse circulatory shunt'. Intrauterine death occurred at 28 weeks' gestation. An autopsy showed absent aortic valve leaflets but three tiny membranous remnants. Hemodynamic evaluation by fetal echocardiography should include the documentation of the presence of and assessment of the grade of aortic regurgitation, mitral regurgitation and blood flow through a foramen ovale as well as left ventricular function.