DEFINITION OF INSEPARABLY FUSED VENTRICULAR MYOCARDIUM IN THORACOPAGUS - FETAL ECHOCARDIOGRAPHIC UTILITY AND PATHOLOGICAL REFINEMENT

Correlative echocardiographic and pathological findings in a thoracopa gus with conjoined hearts are reported. One twin had tricuspid atresia with discordant atrioventricular connections and concordant ventricul oarterial connections. The morphologic right ventricle was hypoplastic and there was a large muscular ventricular septal defect. The other t win had hypoplasia of the mitral valve anulus and left ventricle with double-outlet right ventricle and pulmonary valve atresia. The tricusp id valve was severely insufficient in part because of a large orifice and redundant, elongated leaflets with abnormal chordal attachments. T he left ventricles of these two twins shared a perforated common ''fre e wall'' with at least two large defects allowing mixing of the circul ations at that level. Not all anatomic details were established conclu sively by fetal echocardiography; however, sufficient diagnostic infor mation was obtained to support a decision not to aggressively resuscit ate these twins after elective cesarean delivery at 31 weeks' gestatio n.