MORBID ANATOMY IN NEONATES WITH EBSTEINS-ANOMALY OF THE TRICUSPID-VALVE - PATHOPHYSIOLOGIC AND CLINICAL IMPLICATIONS

The hearts of six neonates with Ebstein's anomaly of the tricuspid val ve who died in the 1st month of life were compared with hearts of six age- and size-matched control neonates. All six hearts had morphologic ally severe disease with gross right atrial dilation and marked apical displacement of the tricuspid valve. All had a secundum atrial septal defect and four had additional cardiac lesions (pulmonary atresia in two, ventricular septal defect in two). There was significant thinning of the right ventricular free wall distal to the tricuspid valve (3 /- 0.2 mm vs. control 4.2 +/- 0.2, p < 0.01) and right ventricular fib er diameter was reduced (7.2 +/- 0.3-mu-m vs. control 11.4 +/- 0.6, p < 0.001). The fibrous tissue content of both right and left ventricula r free walls was increased (right, 29.3 +/- 2.6% vs. control 8.7 +/- 1 .1, p < 0.001; left, 23.2 +/- 1.5% vs. control 8.5 +/- 0.7%, p < 0.001 ). Although the right ventricular abnormalities might be explained by hemodynamic stress in utero, abnormalities of the left ventricular fre e wall suggest that either genetic or nonhemodynamic environmental fac tors are involved in the morphogenesis of this condition. Increased ri ght and left ventricular fibrosis may contribute to the poor early out come in this group and may predispose to late complications, such as s ubnormal exercise performance, hemodynamic deterioration or late sudde n death that may occur in patients with Ebstein's anomaly who survive the neonatal period.