Epidemiology
HLHS occurs in an estimated 1 out of 3,841 live births in the United States, or an estimated total of 1,025 live births per year in the US. Overall, it is estimated to make up 2-3% of all cases of congenital heart disease, and is the most common single-ventricle defect. It is thought to be more common in male infants, 1.5 times as common as in female infants. A recent systematic review found a slight decrease in prevalence of HLHS from 0.689/1000 in 1995 -1999, to 0.475/1000 in 2010 - 2017. This is thought to be due to improvements in prenatal detection and prenatal counseling and subsequent pregnancy. Signs and symptoms
Closing of the ductus arteriosus in a heart that is severely underdeveloped on the left results in cyanosis and respiratory distress which can progress to cardiogenic shock and death. Early symptoms might include poor feeding or cyanosis that does not respond to oxygen administration. Peripheral pulses may be weak and extremities cool to the touch.HLHS often co-occurs with low birth weight and premature birth.In neonates with a small atrial septal defect, termed "restrictive", there is inadequate mixing of oxygenated and deoxygenated blood. These neonates quickly decompensate and develop acidosis and cyanosis.On EKG, right axis deviation and right ventricular hypertrophy are common, but not indicative of HLHS. Chest x-ray may show a large heart (cardiomegaly) or increased pulmonary vasculature.
Hybrid procedure
The Hybrid procedure may be used in place of the Norwood. The Hybrid procedure does not necessitate the use of heart-lung bypass or performing a sternotomy. Instead of a six-hour surgery, the Hybrid typically takes one to two hours. In this procedure, a stent is placed in the ductus arteriosus to maintain its patency, and bands are placed over both the left and right pulmonary artery branches to limit pressure and over-circulation to the lungs. Outcomes with the Hybrid approach are comparable to those with the Norwood. Glenn procedure
The second stage—the bidirectional Glenn or Hemi-Fontan (see also Kawashima procedure)—relieves some of the problems introduced by Stage I palliation. In this operation, the superior vena cava is ligated from the heart and connected to the pulmonary circulation. At this time, the Blalock-Taussig or Sano shunt is taken down. The lungs are no longer exposed to systemic arterial pressures, but much lower venous pressures. Although venous blood from the upper half of the body is no longer mixing with oxygenated blood in the right ventricle, there is still venous mixing from the lower half of the body, leading to some degree of oxygen desaturation. Fontan procedure
The final procedure, the Fontan procedure, completes the repair of the hypoplastic left heart. Although there are several variations, the functional effect is to redirect venous blood from the lower body (through the inferior vena cava) away from the right atrium to the pulmonary artery. This should eliminate any mixing of oxygenated and deoxygenated blood in the right ventricle.