Introduction

Hypoplastic left heart syndrome (HLHS) is the term applied to a spectrum of lesions characterized by underdevelopment of the left ventricular outflow tract and aortic valve combined with additional hypoplasia of the left ventricle and mitral valve and as a consequence, the left heart is unable to support the systemic circulation.[1],[2],[3],[4],[5],[6],[7] As described in Chapter 2 of the Pediatric and Congenital Cardiac Section of this STS E-Book, both The International Paediatric and Congenital Cardiac Code (IPCCC) and the Eleventh Iteration of the International Classification of Diseases (ICD-11) state that “Hypoplastic left heart syndrome is defined as a spectrum of congenital cardiovascular malformations with normally aligned great arteries without a common atrioventricular junction, characterized by underdevelopment of the left heart with significant hypoplasia of the left ventricle including atresia, stenosis, or hypoplasia of the aortic or mitral valve, or both valves, and hypoplasia of the ascending aorta and aortic arch.” HLHS is a rare disease with an incidence of 0.016% to 0.036% of live births and constituting 1.4% to 3.8% of congenital heart disease (CHD) in autopsy series.[8] Among live born affected individuals, males are more frequently than females.[9],[10]

Long term survival is only possible with a series of cardiac operations or heart transplantation, and without surgical intervention, the mortality rate of HLHS exceeds 90% in the first year of life. With surgical intervention the one year survival rate is between 64 and 74%.[11] In the United States, non-operative, comfort care is selected by as many as 15%.[12]