Criss cross heart: an outflow tract defect?

Criss-cross heart (CCH) is a rare congenital malformation in which the atrioventricular inflow vectors are approximately perpendicular. CCH is associated with other defects including malposition of the great arteries, supero-inferior ventricles, and ventricular septal defects (VSD). A recent study in a mouse model demonstrates that CCH and associated malformations can be the result of a growth arrest of the outflow tract. In order to confront this hypothesis, we studied 16 cases of criss-cross heart with detailed anatomical description and clinical outcomes. All patients with criss-cross heart diagnosed in Necker –Enfants Malades Hospital from 1999 to 2022 were included in a retrospective study. Echocardiography, CT scans and anatomical MRIs were reviewed. Segmental analysis according to Van Praagh was SDL in 11 patients, SDD in 4 and SDA in 1. The ventricles were supero-inferior in 12 patients (75%). Ventriculo-arterial connections were always abnormal: double outlet right ventricle in 15/16 with a bilateral conus in 11 and a subaortic conus in 4, transposition of the great arteries in 1. The pulmonary valve was stenotic or atretic in 12 patients (75%). All patients had a VSD opening in the inlet of the right ventricle: inlet only in 8 patients, confluent inlet/outlet in 6, inlet with muscular extension in 2. Fifteen (94%) patients underwent surgery, univentricular repair in 13/16 (81%), biventricular in two. Criss-cross heart is always associated with a malposition of the great vessels and a VSD, always of the inlet type. Anatomical characteristics are similar to the ones observed in the mouse model for CCH, suggesting similar developmental mechanisms. The malposition of the great vessels might be due to a defective growth of the outflow tract. The constant finding of a VSD of the inlet type is consistent with an abnormal rotation of the atrioventricular canal.