A study was undertaken to determine the early and long-term outcomes dictated by the Fontan state per se (a state in which the force driving pulmonary blood flow is solely or largely a residue, in the systemic venous pressure, of the main ventricular chamber's contractile force) and the transition (by surgery) to it from the state of congenital heart disease under optimal conditions (after a "perfect" Fontan operation). The primary study design used a solution of a multivariate risk factor equation for death, by which survival rate under optimal conditions was predicted to be 92%, 89%, 88%, 86%, 81%, and 73% at 1 month, 6 months, and 1, 5, 10, and 15 years, respectively, after the Fontan operation. The hazard function (instantaneous risk of death at each moment in time after the operation) had an early rapidly declining phase of hazard that at about 6 months began to give way to a late hazard phase, which was rising by about 6 years after surgery. A secondary study design, using the theory of competing risks, yielded survival and hazard function information very similar to that of the primary study design. The Therefore, a study was undertaken with the objective of determining the long-term outcome dictated by this unusual state, and by the operation required to create it, performed under optimal circumstances. Succinctly, outcome after a "perfect" Fontan operation was sought.
Methods
Study DesignTime-related survival and functional status were the outcome events selected for the study. Patients with hemodynamic and objective exercise data were too few to be studied or to be considered representative of the group as a whole. The objective of the study could not be met simply by describing the time-related survival rate and functional status of a large group of patients who had undergone the Fontan operation because both are adversely affected by circumstances not necessarily present in either the Fontan state per se or in the transition to it by surgery under optimal circumstances. Therefore, a design was adopted that sought to eliminate the effect of such circumstances, leaving only the effects of the Fontan state itself and the transition to it (by surgery) under optimal circumstances. A secondary and somewhat different design for the study of survival was also adopted to determine if the Values are for patients exclusive of those who underwent takedown of Fontan operation (n=7) or cardiac transplantation (n=4). Note: Time-related instantaneous risk of death in four modes is shown in Figure 4 (see text).answer to the question posed would be the same using a different design theory.
Pnimary DesignThe survival and hazard functions for the total group of 334 patients were determined, retaining all patients up to the time of the last follow-up. A
