Horizontal ventricular septum with dextroversion: hearts with and without aortic atresia.

Two hearts with horizontal ventricular septum, dextroversion (situs solitus), ventricular septal defects, and malaligned great vessels are reported. One of the hearts had aortic atresia and the infant died; the other patient had a Fontan-type physiologic correction. Reviewing the literature, the following conclusions are drawn: (a) Hearts with horizontal ventricular septum and those with criss-cross atrioventricular connections may be the result of different degrees of rotation of the ventricular muscle mass. This rotation is not likely to be postseptational but preseptational. (b) Only those hearts with a complete 180 degrees rotation should be called criss-cross hearts. (c) Partial rotation results in a horizontal septum such that the right ventricle is invariably superior, regardless of atrioventricular concordance or discordance, situs solitus or inversus, or dextroversion. (d) Physiologic surgical correction is often possible but has to be tailored to the details of each heart.