Ectopia cordis and cleft sternum: evidence for mechanical teratogenesis following rupture of the chorion or yolk sac.

We present case material and a literature survey to document the association between ectopia cordis and band disruption anomalies. The occurrence of thoracic ectopia cordis with a cephalic-pointing cardiac apex suggests an arrest of cardiac descent at 3 weeks of development, consistent with our finding of ectopia cordis in a 28-day human embryo. Mechanical compression secondary to rupture of the chorion and/or yolk sac at 3 weeks of gestation would interfere with normal cardiac descent and compress the chest, yielding thoracic and pulmonary hypoplasia. Congenital heart defects associated with ectopia cordis may represent deformations secondary to mechanical distortion of the developing heart following early rupture of the chorion and/or yolk sac. As is illustrated by our clinical specimens, tethering of the heart to periumbilical structures by bands could yield thoracoabdominal ectopia cordis. The milder anomaly of cleft sternum, which is also associated with band disruptions, may occur later in development following rupture of the chorion, yolk sac, or amnion.