The syndrome of left isomerism: sonographic findings and outcome in prenatally diagnosed cases.

Objective: The purpose of this study was to evaluate the accuracy of the prenatal diagnosis of left isomerism and to assess possible diagnostic and prognostic markers.

Methods: We conducted a retrospective review of all previously unpublished cases of left isomerism diagnosed in the prenatal and postnatal periods in 2 tertiary referral centers in Germany over 15 years.

Results: Among 34 fetuses, 31 had a correct prenatal diagnosis of left isomerism; 31 had an interruption of the inferior vena cava with azygos continuation; 22 had different types of viscerocardiac heterotaxy; 13 had heart block; and 28 had cardiac defects, with a high prevalence of atrioventricular septal defects (n = 24), right outflow tract obstruction (n = 11), double-outlet right ventricles (n = 6), and anomalous pulmonary venous return (n = 6). Among the 34 cases, 9 underwent termination of pregnancy; 2 fetuses died in utero; 5 children died in the neonatal period; and 4 children died in infancy. Only the presence of heart block and hydrops was significantly correlated with nonsurvival (P < .05). Fourteen children survived, with a mean follow-up +/- SD of 2.9 +/- 2.6 years. Three survivors underwent single-ventricle palliation, and 1 had successful biventricular repair. Three children were awaiting cardiac repair. The remaining 7 children had minor or no associated cardiac defects and were doing well.

Conclusions: Prenatal diagnosis of left isomerism is feasible, with high accuracy. Important diagnostic pointers are viscerocardiac heterotaxy, complex cardiac malformations, heart block, and interruption of the inferior vena cava. The mortality in fetuses and neonates is high in the presence of heart block and hydrops, whereas the cardiac defects influence the long-term outcome.