The diagnosis of origin of both great arteries from the morphologic right ventricle requires angiocardiographic demonstration that (1) the pulmonary artery and aorta arise from the same ventricle and the anatomic features of the ventricle are those of right ventricular myocardium, and (2) fibrous continuity between the morphologic mitral valve and either semilunar (aortic or pulmonic) valve is absent. The inter-relationship of the great arteries at the level of the semilunar valves varies. The basic anomaly may exist with a normally positioned heart, dextrocardia, ventricular inversion, or common (single) ventricle. Pulmonic stenosis is common and usually is present when isolated dextrocardia exists. Subaortic stenosis may be present. Other cardiovascular malformations also may occur, including abnormalities of the atrioventricular valves, patent ductus arteriosus, right aortic arch, isolation of the left subclavian artery, hypoplastic left ventricle, peripheral pulmonary artery stenosis, coarctation of t...