Recovery of respiratory gas exchange after exercise in adults with congenital heart disease.

Background: Delayed gas exchange kinetics in the early recovery period after exercise testing has been reported in children and adults with congenital heart disease (ACHD). Our objective was to compare early and late phase recovery kinetics in three groups of ACHD-patients.
Methods: Sixty-seven adults with complex ACHD (33 repaired tetralogy of Fallot, 19 Fontan operations, and 15 transposition complexes) and 10 healthy controls underwent symptom-limited cardiopulmonary exercise testing measuring gas-exchange kinetics over a 10 minute recovery period. Changes within the first minute of recovery and late changes, characterized as the time to reach 50% of peak values (T1/2), were compared between groups.
Results: Recovery of VO2 in early and late recoveries was significantly delayed in all ACHD-patients compared to controls without significant differences between patient groups. VO2-recovery at 1 min compared between patients and controls was -7.2 ± 4.0 versus -17.0 ± 4.5 ml · kg · min(-1) and T1/2 VO2 was 147 ± 62 versus 66 ± 23 s (p < 0.0001 for both comparisons). Similar changes were observed for VCO2-recovery. Peak VO2 (ml · kg · min(-1)) demonstrated strong correlation with VO2-recovery at 1 min (ml · kg · min(-1), r=0.90) and moderate correlation with T1/2 VO2 (r = -0.70).
Conclusion: Gas exchange recovery after exercise testing is prolonged in ACHD-patients, independent of the congenital heart lesion but related to peak aerobic capacity, particularly recovery kinetics within the first minute. Recovery kinetics at 1 min is a useful and easily obtained clinical measure that warrants further study as a prognostic measure.
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