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4h-1. Hypoplastic left heart syndrome. (Legend.)

A. There is marked cardiomegaly with passive venous congestion. The endotracheal tube, nasogastric tube and umbilical arterial line are in appropriate position.

4h-2. Hypoplastic left heart syndrome.

A. There is marked cardiomegaly with passive venous congestion in this newborn who presented with shock.

B. Frame from a cineangiogram demonstrates severe hypoplasia of the ascending aorta.

Hypoplastic left heart syndrome

Hypoplastic left heart syndrome describes a group of conditions characterized by malformations including mitral valve stenosis/hypoplasia/atresia, aortic valve stenosis/hypoplasia/atresia,

In combination with varying degrees of hypoplasia of the left ventricle and the aortic arch. Approximately 85% of patients have some combination of atresia or stenosis of the aortic and mitral valves. The other 15% have complete atrioventricular septal defect with malalignment of the common AV valve to the right, resulting in hypoplasia of the left ventricle.

HLHS occurs in approximately 1.4-3.8% of congenital heart disease although it is responsible for 23% of deaths in the newborn period.

There is a slight male preponderance.

Presentation: These children present early in the newborn period often with acute cardiovascular collapse, cyanosis, shock and acidosis. This occurs following ductal closure and may be prevented with the institution of prostaglandins.

Physical findings: Infants will have varying degrees of desaturation. The pulses will be weak according to the degree of ductal constriction. There is a prominent right ventricular heave with a diminished left ventricular impulse. On auscultation there is a normal first heart sound with a single prominent second heart sound. Approximately 1/3 patients have a gallop.

There may be an apical diastolic rumble. The liver is enlarged.

CXR: Typically there is cardiomegaly with increased pulmonary vascular markings.

ECG: Variable, typically there is a right axis deviation, with right ventricular hypertrophy and diminished left heart voltages. There may be a leftward superior axis in patients with a malaligned common AV septal defect.

Treatment: This represents one of the most difficult management decisions in pediatric cardiology with the longterm outcome a Fontan physiology supported by a systemic right ventricle. The Norwood procedure consists of initial placement of a systemic to pulmonary artery shunt with incorporation of the aorta and pulmonary arteries into a single outlet vessel. This is performed in the first weeks of life. The second procedure is a Glenn cavopulmonary anastomosis performed between six months to a year. The third procedure is a Fontan palliation, which is generally performed between 18 months to 36 months of age. In some patients an atriopulmonary communication with a fenestration will be performed to reduce atrial hypertension which can be closed either surgical as a fourth procedure or by transcatheter closure in the catheterization lab.