Maximal aerobic capacity (VO₂ max) has already been reported in patients with congenital heart disease (CHD). We postulate CPET parameters does not reflect cardiac performance in these patients. We compared VO₂ max and maximal systemic stroke volume (SV max) in a population of children with repaired CHD. Impedance cardiography is considered accurate for stroke volume (SV) measurement during exercise testing.

VO₂ max and SV max (using impedance cardiography analysis device, Physioflox^®) were measured during an upright ramp incremental cycle exercise in children with repaired congenital heart disease. Three groups were studied: G1 no residual disease n=23, G2 with residual left heart obstruction n=15, G3 with residual right heart obstruction and/or regurgitation n=40. The results were also compared with comparable healthy control population (G0 n=25).

No significant correlation between SV (mL/m²) and VO₂ max and maximal oxygen pulse (% Th) was found in all the groups. Compared to controls (G0), stroke work was lower in patients with residual lesions (P<0.01) but was similar in patients with no lesions and controls. Peak SV was decreased significantly in G2 (49mL/m²) and G3 (46.95mL/m²) G0 with residual left or right lesions compared to G0 (G0 54.22mL/m²) P<0.001 while SV max in G1 was not impaired (57.8mL/m²).

As expected, SV max was impaired in children residual lesion after CHD repair. VO₂ max and maximal oxygen pulse does not seem to reflect cardiac performance. Concomitant noninvasive SV max measurement during CPET appears to be useful to evaluate these patients during their follow-up.