Exercise Tolerance in Patients who Underwent Fontan Procedure

Abstract

1087 BACKGROUND: Fontan heart surgery should, by itself, enhance exercise capacity. Several studies demonstrated persistent reduced exercise capacity compared to healthy children, even after the intervention. Further, skeletal muscle function (SMF) was never evaluated in these patients. PURPOSE: To evaluate, despite the known limitations derived from the abnormal cardiopulmonary function, the role of SMF on exercise tolerance of these patients. METHODS: We evaluated functional capacity of seven patients who underwent Fontan procedure (FP) (118 ± 75 months post surgery; mean ± SD) (age = 16 ± 5 y) and seven healthy children (HS) (19 ± 7 y) paired for age, sex, height and weight. Evaluation included neuromuscular function assessment using the Piepoli's ergoreflex protocol. A ramp exercise protocol performed on bicycle ergometer with breath by breath gas exchange analysis was also performed. RESULTS: Lower maximal workload (103 ± 42 vs 176 ± 63 watts), lower maximal heart rate (156 ± 27 vs 184 ± 9 bpm) and maximal SaO2 (91 ± 4 vs 99 ± 2%) were observed for FP vs HS respectively (all p<0.05). Maximal ventilatory equivalents for oxygen (VE/VO2) and carbon dioxide (VE/VCO2) were higher for FP than HS (VE/VO2: 46.1 ± 8.3 vs 37.1 ± 6.6; VE/VCO2: 40.5 ± 7.5 vs 31.2 ± 6.4; all p<0.05). Time to fatigue of non-dominant forearm muscles was lower for FP vs HS (431 ± 290 vs 847 ± 347 s; p<0.05). The ergoreflex contribution to absolute diastolic blood pressure (DBP) was higher (12.5 ± 4.8 vs 5.6 ± 4.2 mmHg; p<0.05) for FP vs HS. Finally, muscle strength of quadriceps femoris and non-dominant forearm muscles correlated significantly to VO2 peak for FP (r = 0.838; p<0.05 and r = 0.895; p<0.01 respectively). CONCLUSION: These results are in agreement with existing data concerning the reduced exercise capacity of FP compared to HS. Of interest, skeletal muscle endurance and strength are reduced for FP and the ergoreflex contribution is larger on the response to exercise for DBP for FP vs HS. Thus, in addition to the cardiopulmonary function, skeletal muscle function might play also an important role in reduced exercise tolerance of these patients. Supported by the Quebec Heart Institute