We describe the pre- and postoperative determinants of cardiorespiratory function after the modified Fontan operation for 60 patients operated at Mayo Clinic between 1985 and 1993. The patients were 5 to 41 years of age(m=[horizontal bar over]14 yr.) at the time of exercise. Exercise was performed 0.8 to 15 years following operation (m=[horizontal bar over]6.4±2.9yr.). The dependent variables at peak exercise included: O2 consumption (˙VO2/kg2/3), systemic arterial O2 sat and HR. We analyzed 126 pre- and 61 postoperative independent variables. Multiple linear regression using a stepwise approach was used to identify predictive variables.

Results: At peak exercise ˙VO2/kg2/3 was 0.086±0.022(0.040 to 0.139) l/min/kg2/3, O2 sat was 89.5±4.1(77-96)% and HR was 147.8±24.4(79-188) bpm. At a p value< 0.05, there were no significant predictors for HRmax. The predictors for˙VO2/kg2/3 and O2 sat are shown in thetable:

Table 1
Full size table

Conclusion: Cardiopulmonary exercise physiology after the modified Fontan operation is complex and is affected by numerous pre-and postoperative variables. It is particularly interesting that the presence of a Glenn anastomosis affects the level of O2 sat at peak exercise. This suggests the presence of intrapulmonary shunting after the Glenn anastomosis.