Proximal shunt origin Advantages Disadvantages Systemic artery Better pulmonary artery growth Decreased coronary perfusion pressure Right ventricle Increased coronary perfusion pressure Potential decreased right ventricular function Potential increased ventricular arrhythmias Decreased pulmonary art

Ming-Sing Si, Gail D Pearson and Richard G Ohye* Department of Cardiac Surgery, Michigan Congenital Heart Center, C.S. Mott Children’s Hospital, Room 11-735, 1540 E. Hospital Drive/SPC 4204, Ann Arbor, MI 48109-4204, USA National Heart, Lung, and Blood Institute/NIH, 6701 Rockledge Drive, Room 8132, Bethesda, MD 20892, USA C.S. Mott Children’s Hospital, Room 11-742, 1540 E. Hospital Drive/SPC 4204, Ann Arbor, MI 48109-4204, USA *Author for correspondence: Tel.: +1 734 936 4978 Fax: +1 734 232 8595 ohye@umich.edu Hypoplastic left heart syndrome, the most common complex congenital heart malformation, is characterized by underdeveloped left-sided heart structures. The Norwood procedure followed by two-staged operations has permitted the extended survival of many of these patients. Survival, however, remains suboptimal with most of the morbidity and mortality occurring during the Norwood procedure hospitalization. The modified Blalock–Taussig shunt has been implicated in contributing to the mortality risk due to decreased systemic diastolic blood pressure and coronary perfusion. Therefore, the right ventricle-to-pulmonary artery shunt was recently reevaluated as a lower-risk source of pulmonary blood flow in the Norwood procedure. The Pediatric Heart Network Single Ventricle Reconstruction trial, sponsored by the NIH National Heart, Lung and Blood Institute, evaluated the two types of shunts during the Norwood procedure. This randomized clinical trial has yielded important insight into the effects of shunt selection on morbidity, mortality, hemodynamics and overall current outcomes for hypoplastic left heart syndrome.