Cardiorespiratory response to exercise after modified fontan operation: Determinants of performance

Objectives. This study sought to measure the cardiorespiratory responses to exercise and to identify the perioperative determinants of exercise performance in children, adolescents and young adults who underwent the modified Fontan operation. Background. Several studies of the cardiorespiratory responses to exercise after the Fontan operation have demonstrated subnormal maximal oxygen uptake and exercise heart rate, but the perioperative variables that ultimately affect exercise responses have not been assessed systematically, Methods. The study included 59 of the 548 patients who underwent a modified Fontan operation between January 1, 1984 and December 31, 1993 at the Mayo Clinic. Spirometry was performed at rest in all patients before exercise testing. The patients then exercised using a previously calibrated cycle ergometer and a 3-min incremental cycle exercise protocol. Multiple linear regression analysis was used to determine a subset of variables associated with oxygen uptake at peak exercise (over dotVO(2)max), blood oxygen saturation (O(2)sat) and heart rate at peak exercise (HRmax). Results. over dotVO(2)max ranged from 29% to 95% of normal value; O(2)sat at peak exercise ranged from 77% to 96%; and HRmax ranged from 39.7% to 97.4% of normal value. Multivariate analysis showed that log over dotVO(2)max/kg(2/3) was associated with age at exercise, male gender, body surface area, preoperative confluent pulmonary arteries and rest over dotVO(2)max/kg(2/3). Preoperative left pulmonary artery stenosis, the presence of a classic Glenn anastomosis at exercise and rest O(2)sat were associated with O(2)sat at peak exercise. Age, body surface area at exercise, heart rate at rest and diastolic blood pressure were associated with HRmax at exercise. Conclusions. Subnormal over dotVO(2)max and HRmax values were demonstrated at peak exercise. Several perioperative variables were associated with over dotVO(2)max and O(2)sat at peak exercise. The presence of a classic Glenn anastomosis,vas associated with decreased O(2)sat at peak exercise, suggesting intrapulmonary shunting with the classic Glenn anastomosis. (C) 1997 by the American College of Cardiology.