Rules for the diagnosis of visceral situs, truncoconal morphologies, and ventricular inversions

A series of rules for the diagnosis of visceral situs, truncoconal morphologies, spatial position of the ventricles, and atrioventricular relations are presented. These rules are based on anatomoembryologic concepts and therefore they are applicable to the radiologic and angiocardiographic study of congenital cardiopathies. 1. 1. A situs solitus is characterized because of the presence of an anatomically right atrium placed on the right, which is identified radiologically by the right-sided position of the suprahepatic portion of the inferior vena cava. Situs inversus is characterized by an anatomically right atrium placed on the left, which is identified radiologically by the left position of the suprahepatic portion of the inferior vena cava. 2. 2. In order to diagnose truncoconal morphologies, it is necessary to specify first the presence of one or two arteries arising from the heart. If a single artery arises from the heart, it is a common trunk. When two arteries arise from the heart there are two main truncoconal morphologies: (a) the arteries cross each other in space—the pulmonary artery crosses obliquely in front of the aorta, and (b) transposition of the great arteries—the aorta is then anterior and parallel to the pulmonary artery. 3. 3. By means of the truncoconal morphologies, the spatial position of the ventricles is identified. When the arteries cross each other (without transposition) the right-to-left direction of the pulmonary artery indicates that the anatomically right ventricle is placed on the right side and vice versa. When the great arteries are transposed, the right-sided position of the aorta with respect to the pulmonary artery indicates that the anatomically right ventricle is on the right side and vice versa. The direction of the common trunk from right to left indicates the right-sided position of the anatomically right ventricle and vice versa. This rule is also valid for lateral positions of the great arteries (dextro- and levopositions). 4. 4. Once the visceral situs is diagnosed by means of the position of the suprahepatic segment of the inferior vena cava and the spatial position of the ventricles is ascertained by means of the truncoconal morphologies, one proceeds to establish the atrioventricular relations which number two for each situs—normal atrioventricular relation (atrioventricular concordance) or ventricular inversion (atrioventricular discordance).