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Hypoplastic left heart syndrome

David R Fulton, MD
Section Editor
John K Triedman, MD
Deputy Editor
Carrie Armsby, MD, MPH


Hypoplastic left heart syndrome (HLHS) is characterized by a diminutive left ventricle incapable of supporting the systemic circulation. Surgical and medical interventions have improved outcomes of this condition, which untreated is fatal. However, mortality remains high, with a five-year survival rate of about 65 percent even after surgical repair.

The etiology, diagnosis, clinical features, and management of hypoplastic left heart syndrome will be reviewed here. Management of patients following the Fontan procedure is discussed in further detail separately. (See "Management of patients post-Fontan procedure".)


HLHS accounts for 2 to 3 percent of all congenital heart disease, with a prevalence rate of two to three cases per 10,000 live births in the United States [1,2]. HLHS is the most common form of functional single ventricle heart disease [3]. An analysis of the National Inpatient Sample database reported an estimate of 16,781 cases of HLHS among neonates born between 1988 and 2005 in the United States [4]. A male predominance (male to female ratio approximately 1.5:1) is observed in most population-based and clinical studies [4,5]. The reported overall incidence is likely underestimated because of the indeterminate rate of spontaneous abortions and elective termination of pregnancy of affected fetuses.

Despite its low incidence relative to other congenital cardiac disorders, HLHS, if left untreated, is responsible for 25 to 40 percent of all neonatal cardiac deaths.


The Society of Thoracic Surgeons Congenital Heart Surgery Nomenclature and Database Project anatomically defines HLHS as "a spectrum of cardiac malformations with normally related great arteries…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 arch" [6]. In clinical settings, the anatomic variants of the disease are often distinguished by the status of the left heart valves (eg, mitral stenosis with aortic atresia) (figure 1). At one extreme of this anatomic spectrum, atresia of both the mitral and aortic valves is associated with either an absent or a slit-like left ventricular (LV) cavity and diminutive ascending aorta. With no possibility of LV output, this anatomic subtype is unequivocally identified as HLHS. At the opposite end of the spectrum is the "borderline left heart" in which left heart valves are patent and near-normal in size, but LV hypoplasia and serial left heart obstructions result in the dependence on a postnatal patent ductus arteriosus to maintain adequate systemic circulation. At this end of the spectrum, the need for a Norwood stage I type intervention becomes the defining feature of a diagnosis of HLHS.

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Literature review current through: Oct 2017. | This topic last updated: Oct 26, 2017.
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