Abnormalities seen in the four-chamber view

In HLHS there is a combination of severe obstructive lesions, including atresia or severe stenosis of the mitral and aortic valves, associated with hypoplasia of the left ventricle. In the four-chamber view, the atrioventricular valve does not open on the left side and there is no demonstrable flow from the left atrium to the left ventricle on pulsed-wave or colour Doppler. The left ventricle appears small, echogenic or slit-like with poor contractility. The left atrium is also small and at the foramen ovale there is a reversed flow from left to right. Occasionally the foramen ovale is restrictive and therefore the left atrium appears enlarged.

A further element of the HLHS is hypoplasia of the ascending aorta and aortic arch. The aorta is receiving less blood flow than normal and it consequently appears small by comparison with a large pulmonary artery. There is reverse flow on pulsed-wave or colour Doppler in the aortic arch, as the head and neck vessels and the coronary arteries are fed in retrograde fashion from the arterial duct.

Prevalence

This defect is found in about 1 in 10,000 livebirths.

Other abnormalities

This defect is associated with chromosomal anomalies, mainly monosomy X and trisomy 18.

Prognosis

Postnatally, only palliative treatment is possible. This involves staged surgeries leading to a one ventricle circulation (Fontan type). The quality of life is impaired and life expectancy curtailed with a cumulative mortality of 40% by five years of age.