Measures of exercise capacity in adults with congenital heart disease

Background: Exercise capacity in grown-ups with congenital heart disease (GUCH) is mostly reported by peak oxygen consumption (peak VO(2)). Our aim was to evaluate the maximal character of exercise tests, and to investigate submaximal measures of exercise capacity.

Methods: Adults with Coarctation of the Aorta (COA, n=155), Tetralogy of Fallot (TOF, n=98), dextro-Transposition of the Great Arteries (dTGA, n=68) and Univentricular Heart (UVH, n=10), and 122 healthy adults performed cardiopulmonary exercise testing until exhaustion. Gas exchange was measured breath by breath. The maximal performance of the test was evaluated by respiratory exchange ratio (RER), ventilatory equivalent for oxygen and Borg scale. Oxygen uptake efficiency slope (OUES), VE/VCO(2) slope and VO(2)/WR slope were calculated and ventilatory anaerobic threshold (VAT) was defined. Correlations of these measures with peak VO(2) were calculated.

Results: GUCH showed significantly lower peak VO(2) than controls (p<0.001), declining from 80% in COA, 74% in TOF, 64% in dTGA, to 55% in UVH. Compared to suggested criteria, mean peak RER and median Borg scale indicated a maximal effort in GUCH, however these results were significantly lower than controls (p<0.05). OUES, VO(2)/WR slope and VAT were significantly lower in patients compared to controls. OUES (r=0.853) and VAT (r=0.840) correlated best with peak VO(2); VO(2)/WR slope (r=0.551) and VE/VCO(2) slope (r=-0.421) correlated to a lesser degree (p<0.001).

Conclusion: The investigated GUCH show reduced exercise tolerance compared to controls, related to the underlying heart defect. Different expressions of exercise tolerance clearly reveal the same differences in exercise capacity across groups of GUCH.