Hypoplastic Left Heart Syndrome (HLHS)

---

Hypoplastic left heart syndrome is characterized by many different combinations of heart defects that have in common a very small left ventricle which is not sufficient to pump blood under high pressure to the body.  The aortic valve is usually narrowed (aortic stenosis) or totally blocked (aortic atresia).  The ascending aorta is typically quite small.  In hypoplastic left heart syndrome, the right ventricle or pumping chamber must take over and do the pumping to the body; the aorta is also quite small and blood flow to the pulmonary arteries is typically increased at birth.  The infant is maintained on a medication, prostaglandin (PGE1), intravenously from birth to maintain blood flow to the body and lungs through the patent ductus arteriosus or PDA (the blood vessel between the aorta and pulmonary artery) until an operation (Norwood procedure) can be done.

The treatment of these infants requires a three-stage approach, with the first operation (Norwood) in the first week or so of life, the second (bidirectional Glenn procedure or bidirectional cavopulmonary shunt, surgical palliation is done at around 3 to 6 months of age and the final procedure (Fontan Procedure) is performed at about 2 to 3 years of age:

Surgical correction:  The first operation is the most risky, but about 85-90% of infants survive this operation.   The Norwood procedure consists of reconstruction of the tiny ascending aorta and aortic arch using a piece of pulmonary artery from a donor (allograft or homograft), excision of the septum or partition between the two upper chambers of the heart (atrial septectomy) and construction of a conduit or tube of synthetic material (usually Goretex) between the right ventricle and pulmonary arteries (Sano procedure) or between the artery to the right arm and artery to the right lung (modified Blalock-Taussig Shunt or BT shunt).  This operation creates a favorable circulation that allows later stages and procedures to be successful with ultimate separation of the circulation with blood flowing to the body by using the single right ventricle as the main pumping chamber and blood flowing to the lungs without a pump.