**6. Discussion**

The evolution in the medium and long term outcome of patients operated with the original technique described by Fontan in the 70s demonstrated problems with the incorporation of all the systemic venous atrium in the circuit, characterized primarily by supraventricular arrhythmias and formation of thrombi (9,10,11). This is explained by atrial dilatation and inefficient circulation through this atrium which progressively becomes larger. But, changes in surgical techniques have been made to minimize these problems and improve long-term outcome (9).

At present there are different techniques for completion of the total cavopulmonary diversion: the intracardiac lateral tunnel (technique I) and extracardiac conduit (Technician II), which are the most widely used worldwide and are just two ways that we have employed. We have most often used the intracardiac lateral tunnel and extracardiac conduit including for those patients with abnormal systemic venous return and/or lung disease, which is usually seen in patients with heterotaxy syndrome. Regarding the use or non use of fenestration, this has also been the subject of much discussion, there are groups of surgeons that use the fenestration routinely and others who use it selectively (12,13). We are using this routinely in all our patients because pulmonary vascular resistance is a dynamic phenomenon and therefore it is not always easy to predict its behavior during the postoperative period. It seems safer for the patient having a fenestration that allows you to maintain adequate cardiac output during periods of high pulmonary vascular resistance, plus helps reduce the incidence of prolonged pleural effusions, resulting in decreased hospital length of stay (12,13)

With the passage of time have defined a number of criteria considered important for success in the performance of a Fontan-type surgery. These have included age, single ventricle morphology, anatomy of the pulmonary arteries, the atrioventricular valve function among others (14,15).

Kirklin and colleagues (15) reported 102 patients who had Fontan between 1975 and 1985. They found that age less than 4 years was a risk factor for mortality. Subsequently, the Children`s Hospital Boston reviewed 500 patients between 1973 and 1991 and found similar results in relation to age (16). As for the type of functional single ventricle, these techniques have been implemented for patients classically diagnosed with tricuspid atresia, but now with the increased survival of patients diagnosed with hypoplastic left heart syndrome, the question arises about the reduced ability of right ventricle to be able in time to support adequately the work of a single ventricle physiology to complete the process to the Fontan (3,17,18). This perception has not been recently supported (19.20). Mosca and colleagues show their results in 100 patients with Fontan performed between 1992 and 1998. They found no significant difference in the outcome compared to other types of single ventricle (21). Pizarro subsequently concluded that the Fontan can be performed safely in patients with SHIV making some modifications in surgical technique according to ventricular morphology, the mass ratio - volume and hemodynamic parameters, further suggests that Fontan surgery can be successful at earlier ages avoiding long exposure to hypoxia and risk of paradoxical embolism (1).

Our results regarding operative mortality and mid-term survival are comparable to those reported by other groups. In these studies, the mortality rate varied between 0 and 27% with an average of 10.5% and the 5-year survival varied between 81% and 93%, with an average of 87.5% (9,10,22, 23).

In relation to our surgical protocol in stages, 73.9% of patients had a bidirectional Glenn operation around 6 months of age, preparatory for the Fontan operation. The advantages of this strategy have been previously described (24,25,26).

Regarding the use of anticoagulation, we decided to keep our patients with oral anticoagulation for about 6 months with the objective of preventing thrombosis at the site of fenestration, after this period of time, we defined the need to close the fenestration.

This study determined that the average hospital stay was 13.9 days.
