Exercise capacity of a contemporary cohort of children with hypoplastic left heart syndrome after staged palliation.

OBJECTIVE: Outcome of staged palliation for hypoplastic left heart syndrome has improved over the past decades. However, only little is known about the exercise capacity of children with palliated hypoplastic left heart syndrome where a systemic right ventricle supports the systemic circulation. The aim of the study was to assess exercise capacity in a contemporary cohort of children with hypoplastic left heart syndrome palliated in a single centre according to a uniform surgical strategy.
METHODS: Standardised cardiopulmonary exercise testing on a treadmill was performed in 46 consecutive hypoplastic left heart patients (median age: 6.0 (4.1-11.4) years). All but one patient reached the anaerobic threshold. Exercise data were compared to normal values obtained with a similar exercise protocol in a large cohort of paediatric volunteers.
RESULTS: Oxygen uptake at anaerobic threshold (26.9+/-6.0 ml kg(-1)min(-1); 74.5+/-18.2% of predicted) and maximal oxygen uptake (31.0+/-6.8 ml kg(-1)min(-1); 60.8+/-15.0% of predicted) were significantly reduced compared with controls (P<0.0001 for both). The limitation in exercise capacity was due to an impaired rise in heart rate (158+/-23 bpm; 79.7+/-11.5% of predicted; P<0.0001) and oxygen pulse (4.5+/-1.6 ml per beat; 85.5+/-22.0% of predicted; P<0.0001). Furthermore, respiration during exercise was inefficient with an elevated respiratory rate and reduced maximal tidal volume and minute ventilation at maximal exercise.
CONCLUSIONS: The exercise capacity of children with hypoplastic left heart syndrome is markedly reduced. Limitations in heart rate increase and stroke volume augmentation are the major contributors to this. An abnormal ventilatory response to exercise also adds to their limitation in exercise tolerance. However, the degree of physical disability does not justify discouraging these patients from school and leisure sports.