HLHS includes a wide spectrum of diseases characterized by a varying degree of underdevelopment of the left-sided heart structures, including the LV, mitral valve, aortic valve, and aorta.  The RV thus supports both the pulmonary and systemic circulations.  Due to the hypoplastic nature of the aorta, the systemic circulation is dependent upon patency of the PDA (via medical therapy with PGE-1).

Pulmonary venous return mixes in the right atrium via an ASD or anomalous venous connection.  Associated non cardiac abnormalities are common (25%), and 5% will have a trisomy syndrome.

Neonates may appear normal at birth, but become tachypneic and pale within hours to days, and may progress rapidly to acidosis, cyanosis, and hemodynamic collapse.

Symptoms are dependent upon the size of the inter-atrial communication as this is the only mechanism of getting blood into the systemic circulation (along with a PDA).  Patients with severe restriction at the atrial septum will present with respiratory distress, cyanosis, and acidosis immediately after birth (functionally equivalent to obstructed TAPVR) and require immediate balloon atrial septostomy in the cardiac catheterization lab.

CXR shows mild cardiomegaly and increased pulmonary vasculature.  Echocardiography is the diagnostic study of choice and provides anatomic details about the aortic valve, aorta, coronary anatomy, atrial septum, and other valvular function.  Cardiac catheterization is not routinely performed unless an atrial septostomy is required.

Patients should be treated with PGE1 to maintain ductal patency and supplemental oxygen should be avoided since it causes pulmonary vasodilation and decreases systemic perfusion in the single ventricle child.  Surgical treatment is either by staged palliation ending with the Fontan procedure or by transplantation (see above, Tricuspid Atresia and

the “Single Ventricle Pathway”).  The first stage in palliation is the Norwood procedure.

The procedure may take place under deep hypothermic arrest. The main PA is transected and the diminutive aorta is incisedlongitudinally.  The proximal aorta is anastomosed to the proximal main PA and the aortic arch is augmented with a homograft patch.

PA blood flow is supplied by either a right modified BT shunt (innominate artery to right PA) or a Sano shunt (RV to main PA- see above).  Second and third stage palliation with bidirectional Glenn  and completion Fontan are completed as described for tricuspid atresia above.