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Hypoplastic left heart syndrome describes a range of congenital cardiac lesions, which have in common a small left ventricle which is unable to support the systemic circulation. Typically the volume of the small left ventricle is <20 ml/m2 body surface area (BSA).
A number of fetal cardiac anomalies have been shown to cause this problem—namely, aortic or mitral atresia, with or without mitral or aortic valve stenosis, or an unbalanced atrioventricular septal defect.1 Despite the heart being basically fully developed at some 8 weeks of gestation, the growth of cardiac structures is entirely dependent on a normal fetal circulation. Thus, it comes as no surprise that pronounced aortic stenosis, detected in a fetus at some 18–20 weeks gestation, may progress to present at birth as classical hypoplastic left heart syndrome (HLHS).2
The common presentation of newborns with hypoplastic left heart syndrome at birth is cardiovascular collapse and shock. The peripheral pulses are weak, without major difference between the brachial and femoral pulses. There is usually a mild to moderate degree of cyanosis, but no differential cyanosis. Chest x-ray normally shows cardiomegaly and plethoric lung fields. The ECG documents right ventricular hypertrophy and reduced left ventricular forces. If the diagnosis is suspected, the administration of a prostaglandin infusion at the rate of 5–20 ng/kg/min normally maintains patency of the ductus arteriosus, and will prevent further cardiovascular compromise, progressive acidosis and death. Assessment by cardiac ultrasound will make the definitive diagnosis, allow for optimisation of initial treatment and detailed discussion of the treatment options and outcomes with the parents.
The initial description of a surgical procedure to palliate hypoplastic left heart syndrome in neonates was provided by William Norwood in 1982.3 This allowed neonates to survive into infancy when more palliative surgery was required. The evolution of these techniques has progressed …
Additional references are published online only at http://heart.bmj.com/content/vol96/issue3
Competing interests In compliance with EBAC/EACCME guidelines, all authors participating in Education in Heart have disclosed potential conflicts of interest that might cause a bias in the article. The author has no competing interests.
Provenance and peer review Commissioned; not externally peer reviewed.
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