The Arterial Switch Operation in Transposition of the Great Arteries: Anatomic Indications and Contraindications

Abstract

1. The arterial switch procedure is now the operation of choice for typical D-transposition of the great arteries at The Children's Hospital, Boston, USA, the operative mortality rate since 1985 being 3%. 2. There are many anatomic considerations suggesting the morphologically left ventricle (LV) may well be a better systemic pump than the morphologically right ventricle (RV) which, if true, would favor the arterial switch procedure as opposed to an atrial switch operation: (1) The LV consists almost entirely of the sinus or pumping portion, and has only a minimal distal infundibular (conal) component. The RV, by contrast, has a relatively much larger infundibular component, the primary function of which is to prevent regurgitation rather than to pump. (2) Phylogenetically, the LV is the ancient "professional" pump. By contrast, the RV is a comparatively recent modification of the bulbus cordis. (3) The LV is a two-coronary ventricle, whereas the RV is a one-coronary ventricle. (4) The LV has relatively much more compact myocardium (stratum compactum) than does the RV. (5) The mitral valve leaflets are better designed to occlude a circular systemic atrioventricular orifice than are the tricuspid valve leaflets. (6) The papillary muscles of the LV are large, paired, well balanced, and both arise from the same ventricular wall--the LV free wall. By contrast, the papillary muscles of the RV are comparatively small, numerous, unbalanced, and arise from both ventricular septal and free walls. Hence, dilatation of the LV does not pull the LV papillary muscles apart, whereas dilatation of the RV does pull the RV muscles apart, favoring the development or exacerbation of tricuspid regurgitation. (7) The LV has two conduction system radiations, whereas the RV has only one. 3. The current anatomic contraindications to the arterial switch operation in typical D-TGA include the following: (1) an unprepared LV; (2) an aortic intramural left coronary artery arising from the right coronary sinus of Valsalva; (3) pulmonary outflow tract stenosis (with small annulus and subvalvar obstruction) or atresia; (4) aortic outflow tract stenosis (with small annulus and subvalvar obstruction) with tubular hypoplasia of the aortic arch and preductal coarctation; (5) tricuspid or mitral atresia; (6) marked underdevelopment or absence of either the RV sinus or the LV sinus; and; (7) 2 major anomaly of the systemic and/or pulmonary veins, as in the heterotaxy syndrome with asplenia.(ABSTRACT TRUNCATED AT 400 WORDS)