**3. Surgical palliation of HLHS**

The surgical palliation of HLHS consists of three, staged procedures: the Norwood, the Glenn, and the Fontan procedures.

The goal of the first two procedures is to prepare the heart for the final Fontan procedure. The ventricular function must be preserved by avoiding a pressure load (avoiding a pressure gradient in the aortic arch) or excessive load (correct-sized shunt), minimizing pulmonary vascular resistance (good-sized atrial communication), maintaining optimal pulmonary artery growth, and preserving the tricuspid valve function by avoiding ventricular dilatation associated with excessive volume work by the ventricle.

The first report of an attempted palliative operation for HLHS was in 1977 by Doty and Knott [14]. All the patients described died of poor right ventricular function or coronary ischemia. Norwood and associates reported the first successful palliative procedure that is still performed today [15].

The crucial components of this procedure can be divided into 3 steps:


The Norwood procedure is performed through median sternotomy; under moderate or deep hypothermia, using circulatory arrest or selective cerebral perfusion; the latter is currently the preferred option. Different materials are used for arch reconstruction; homograft is the most common material used, but there are other options including bovine pericardium, core-matrix, and femoral vein graft.

The systemic-to-pulmonary shunt can be performed by using the modified Blalock-Taussing-Thomas shunt (MBTT) (**Figure 1e**) or the right ventricle to pulmonary artery shunt (RVPA) which is named the Sano Shunt (**Figure 1f**).

MBTT shunt is made of polytetrafluoroethylene (PTFE, Gore-Tex): generally 3.5 mm for infants of 2.5–3.5 kg and 4 mm for larger infants.

The 5 mm RVPA shunt is used for neonates between approximately 2.3 and 3.5 kg. If PVR is high, a 6 mm RVPA shunt may be considered.

A randomized clinical trial comparing MBTT and RVPA at 15 North American Centers was performed which includes 275 patients with MBTT and 274 patients with RVPA shunt [16]. Compared with the MBTT group, the patients with RVPA shunt were associated with higher rates of transplantation-free survival at 12 months. By 14 months, the right ventricular end-diastolic volumes were similar in 2 groups [16], however, the RVPA shunt group had more unintended interventions and complications. Data collected over the follow-up period of 32 months showed a nonsignificant difference in transplantation-free survival between the two groups [16].

The second stage procedure is the bidirectional Glenn procedure that consists of a Cavo-pulmonary anastomosis which is usually is performed between 3 and 6 months of age. Viegas et al*.* reviewed 14 years of experience on 36 patients younger than

*Hypoplastic Left Heart Syndrome DOI: http://dx.doi.org/10.5772/intechopen.104723*

90-day-old and reported no mortality, but 90% of patients required Glenn patch augmentation. The indications to perform a Glenn procedure within the first 90 days of life are persistent hypoxemia, signs of ventricular dysfunction, and atrioventricular valve regurgitation [19].

Finally, the third stage procedure is total cavopulmonary connection or the modified Fontan procedure. There are two different surgical techniques for this procedure, namely, the lateral tunnel with intra-atrial PTFE graft and the extracardiac PTFE conduit; these procedures were popularized in an attempt to avoid late supraventricular arrhythmias [20]. The expandable Gore-Tex graft (Peca-labs) allows for dilatation of the Fontan conduit in the cardiac catheterization suite [21].

In 2002, Akintuerk et al. from Giessen, Germany were the first to describe the hybrid approach to HLHS, which is a combination of surgical intervention (application of bilateral branch pulmonary artery bands) and catheter intervention (placement of ductal stent) as primary palliation for neonates with HLHS [22]. In the United States, Galantowicz and Cheatham reported the results of this procedure in 2005 [23].

The results of the Norwood procedure have improved over the last few decades to where it is unethical not to offer this procedure to all newborns with HLHS; cardiac transplant is considered if there is any contraindication for the Norwood operation or Hybrid procedure.
