CARDIORESPIRATORY RESPONSE TO EXERCISE AFTER MODIFIED FONTAN OPERATION - DETERMINANTS OF PERFORMANCE

Objectives. This study sought to measure the cardiorespiratory respons es to exercise and to identify the perioperative determinants of exerc ise performance in children, adolescents and young adults who underwen t the modified Fontan operation. Background. Several studies of the ca rdiorespiratory 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 respon ses have not been assessed systematically, Methods. The study included 59 of the 548 patients who underwent a modified Fontan operation betw een January 1, 1984 and December 31, 1993 at the Mayo Clinic. Spiromet ry 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 regre ssion analysis was used to determine a subset of variables associated with oxygen uptake at peak exercise (over dotVO(2)max), blood oxygen s aturation (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 pe ak 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 su rface area, preoperative confluent pulmonary arteries and rest over do tVO(2)max/kg(2/3). Preoperative left pulmonary artery stenosis, the pr esence of a classic Glenn anastomosis at exercise and rest O(2)sat wer e associated with O(2)sat at peak exercise. Age, body surface area at exercise, heart rate at rest and diastolic blood pressure were associa ted with HRmax at exercise. Conclusions. Subnormal over dotVO(2)max an d HRmax values were demonstrated at peak exercise. Several perioperati ve 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 shu nting with the classic Glenn anastomosis. (C) 1997 by the American Col lege of Cardiology.