Surgery for Aortic Atresia, Hypoplastic Left Heart Syndrome, and Hypoplastic Left Heart Complex

Abstract

Aortic atresia is defined as complete occlusion of the aortic valve. Its isolated form is combined with a nonrestrictive ventricular septal defect (VSD) and usually a normal mitral valve. Hypoplastic left heart syndrome describes a spectrum of malformations in which the left ventricle is unable to support the systemic circulation due to its small size. Its adjacent structures are also severely hypoplastic.

The diagnosis is made by echocardiography. Cardiac catheterization or magnetic resonance imaging (MRI) is necessary only in rare cases.

The systemic circulation and hence survival is depending on a patent ductus arteriosus. Decreasing pulmonary vascular resistance soon leads to increased diastolic runoff and pulmonary congestion. Therefore, preoperative management is based on maintaining an open ductus and on systemic afterload reduction.

The two principal therapeutic options are multistage reconstruction or primary transplantation.

The multistage reconstruction pathway consists of three stages: Norwood procedure, bidirectional Glenn operation, and Fontan completion.

• Stage 1 – The Norwood procedure is based on three principles: unrestricted blood flow from the right ventricle to the systemic circulation, restricted pulmonary blood flow, and unrestricted pulmonary venous return. These goals are achieved by an anastomosis between the main pulmonary artery and the aorta usually using an enlarging patch, an RV-PA conduit, or a modified Blalock-Taussig shunt as the source of pulmonary blood flow and the excision of the interatrial septum. This operation is timed around day 5.

• Stage 2 – A bidirectional cavopulmonary anastomosis replaces the primary source of pulmonary blood flow thus unloading the ventricle. The interval between stage I and stage II varies from center to center. We prefer an interval of 3–4 months and perform a simple bidirectional Glenn anastomosis (see Chap. xy, functional univentricular heart and Fontan operation).

• Stage 3 – The Fontan operation leads to complete separation of the systemic and pulmonary circulation. The total cavopulmonary anastomosis can be achieved by an extracardiac method using PTFE prosthesis or by an intracardiac technique. As aortic cross clamping can be avoided and postoperative arrhythmias might be minimized, we prefer the extracardiac type of the Fontan operation (operative technique see Chap. xy). We usually perform this operation at about 3 years of age, when the patient has a weight of at least 12 kg.

Results of the multistage reconstruction: Total mortality comprises the mortality of each procedure plus the interstage mortality. Survival rates of the Norwood procedure increased from 50 to 70 % in the early days up to more than 90 % nowadays. Our own early survival over the last 10 years in 206 cases was 87.4 %. Interstage mortality rates between stage I and stage II vary between 10 and 16 % and are influenced by the shunt type. Mortality rates between 0 and 2 % are reported for the bidirectional Glenn shunt as well as for the Fontan completion.

The so-called Hybrid procedure postpones the Norwood procedure by initially performing a ductal stent and bilateral pulmonary artery banding. The Norwood operation is done later together with the bidirectional Glenn operation.

Alternatives to the multistage reconstruction are primary heart transplantation or fetal aortic valve intervention if critical aortic stenosis is the primary lesion. The latter method is still in discussion.