Pulmonary atresia with intact ventricular septum (PA-IVS) in monozygotic twins.

Pulmonary atresia with intact ventricular septum (PA-IVS) is a rare congenital heart defect (CHD) of unknown etiology, characterized by an atretic pulmonary valve with the right ventricle varying in size and morphology among different affected individuals. We report on monozygotic (monochorionic diamnionic) twin sisters with PA-IVS who died soon after birth. The patients were prematurely born at 27 weeks by caesarean to a 24-year-old gravida 1, para 0 Hispanic mother. The pregnancy course was previously uneventful, and the mother denied any exposures during pregnancy. Both parents were healthy, nonconsanguineous, with no known family history of CHD in a three-generation pedigree. The Apgar scores were 5 and 7 (Twin A), and 4 and 6 (Twin B), at 1 and 5 min, respectively. Birth weight was 1,050 g (60th centile, Twin A) and 910 grams (40th centile, Twin B), crown-heel length was 35 cm for both twins, and occipital-frontal circumferences were 24.8 cm (Twin A) and 25 cm (Twin B). Soon after birth, Twin A developed increasing respiratory rate requiring mechanical ventilation, and a systolic ejection murmur at the left upper sternal border was noted accompanied by poor oxygen saturations. Chest X-ray revealed hazy, granular lung fields consistent with hyaline membrane disease as well as a cardiac silhouette occupying nearly 70% of the thoracic diameter. An echocardiogram revealed an annular-type pulmonary valve atresia, and aortic stenosis with a bicuspid aortic valve. The left ventricle appeared normal in size and function. In spite of therapy, the patient developed respiratory failure and died at the age of 3 days. TwinB had a similar clinical course and the echocardiogram also showed pulmonary valve atresia (without aortic atresia), suprasystemic right ventricular systolic pressures and moderate tricuspid regurgitation. On day 3 of life, the echocardiogram showed poor cardiac function with left ventricular ejection fraction of 45%. Grade IV germinal matrix hemorrhage was detected by ultrasound. Comfort care was provided, and she died on day 7 of life. Unrestricted postmortem examinations, following perinatal autopsy protocols were performed in both patients. The cardiac findings present in both twins were virtually identical, consistent with the diagnosis of PA-IVS, and characterized by cardiomegaly Twin A: 16.5 g; Twin B: 15.2 g), marked right atrial dilatation, marked right ventricular myocardial hypertrophy (8–10 mm in thickness) and a small right ventricular chamber measuring approximately 9 mm from the atrioventricular annulus to the apical aspect of the chamber. In both cases, the tricuspid valves were dysplastic with two identifiable thick leaflets, attached to the right ventricular endocardium through markedly short and thickened chorda tendineae and papillary muscles. The pulmonary valvewas completely atretic in bothpatients, with three fused valves leaving no identifiable lumen. In addition, in twin A the aortic valve was bicuspid with thick, dysplastic leaflets. All other cardiac structures appeared within normal limits in both twins, and no other dysmorphic features besides the congenital heart defects were present in either twin. In particular, no short sternum, abnormal palmar creases or camptodactyly were noted.