**3. Indications for Fontan operation**

The indications for opting for a Fontan operation are patients who have one functioning ventricle. At first, patients with tricuspid atresia were selected for this procedure [1, 2]. Shortly thereafter, patients with double-inlet left (single) ventricle were added to the indications for Fontan [36]. Following description of surgical palliation of hypoplastic left heart syndrome (HLHS) by Norwood et al. [37, 38] in the early 1980s, HLHS became the major lesion requiring Fontan operation. Subsequently, mitral atresia (with normal aortic root), unbalanced atrioventricular septal defects (AVSDs), pulmonary atresia with intact ventricular septum with markedly hypoplastic right ventricle, and other complex heart defects with one functioning ventricle were selected for Fontan surgery.

Attempts to insert prosthetic ventricular septum for single ventricle patients met with problems, leading to abandoning such procedures. Thereafter, Fontan became a preferred treatment method. With reasonably good results of Fontan, the pendulum swung so that any patient who could not undergo complete repair became a candidate for Fontan.

A middle of the road method, the so-called one-and-one-half ventricle repair was developed for patients with pulmonary atresia with intact ventricular septum with modest-sized right ventricle. In this procedure, a bidirectional Glenn procedure to divert the SVC flow into the PA is performed and allows the small right ventricle to pump the IVC blood into the pulmonary circuit, and the patent foramen ovale is closed. It is generally considered to be a better option than Fontan, although, to my knowledge, there are no comparative studies to assess this issue.

Because of relatively high mortality rates (17.0–31.7%) [39, 40] and low actuarial survival rates (66.5% at 5 years and 64.4% at 15 years) [41] for unbalanced AVSD patients following Fontan, a number of institutions attempted single stage or staged biventricular repair or conversion from single ventricle (Fontan) to biventricular repair [39, 42–47]. Detailed analysis by Nathan et al. [39] suggested that the biventricular repair and conversion from single ventricle (Fontan) to biventricular repair groups had reasonably similar mortality rates and a similar need for cardiac transplantation, but these parameters were lower than those seen in the Fontan palliation cohort.

Cardiac transplantation is a surgical alternative in the management of HLHS [48] and other single ventricle lesions. While heart transplantation was used at several institutions initially for HLHS, because of non-availability of

donor hearts, most institutions have reverted to the Norwood/Fontan route. In addition, following successful cardiac transplantation, multiple medications for the prevention of graft rejection, frequent outpatient visits and periodic endomyocardial biopsy, to recognize rejection very early, are necessary in the management of these children. At the present time, cardiac transplantation is used for patients failing Fontan operation at a limited number of institutions.
