Assessment of progressive changes in exercise performance in patients with a systemic right ventricle following the atrial switch repair

There is a high prevalence of right ventricular dysfunction and reduced exercise performance in survivors of atrial switch repair for transposition of the great arteries. However, it is not known whether the impairment in exercise performance is progressive. We performed paired comparison of exercise performance in 28 patients who underwent two serial incremental exercise tests at an interval of 5.0 +/- 1.4 years between the two tests (age 11.5 +/- 3.7 years at first test, 16.4 +/- 3.6 years at second test). There was no change in the chronotropic response between the two tests. However, there was a reduction in both the peak VO2 (32.5 +/- 8.3 vs 29.6 +/- 5.7 ml/kg/min, p = 0.05) and anerobic threshold (22.1 +/- 5.1 vs 18.3 +/- 4.2 ml/kg/min, p < 0.01) with time. Furthermore, there was a decline in the O2 pulse (oxygen uptake/beat) at anaerobic threshold (% predicted value 95 +/- 23% vs 82 +/- 23%, p =.02), O2 pulse at a heart rate of 140 (% predicted value 100 +/- 30% vs 85 +/- 19%, p = 0.02), and the maximum O2 pulse (z value -0.27 +/- 1.31 vs -1.27 +/- 1.16, p < 0.01) when compared to growth-related normal values. We conclude that there is a progressive reduction in aerobic response to exercise in patients with a systemic right ventricle. The maintenance of chronotropic response suggests that the stroke volume response of the systemic right ventricle during exercise does not increase commensurate with somatic growth.