Abstract
Background: The clinical care of adults with a systemic right ventricle with biventricular circulation (sRV-biV) is influenced by cardiorespiratory fitness (CRF) evaluation. However, prognostic markers for CRF are derived from analyses of adults with a systemic left ventricle (sLV). While some studies suggest that CRF is lower in adults with sRV-biV compared to those with a sLV, they have not controlled for key clinical characteristics and ventricular function of the systemic ventricle. Research Question: Is CRF lower in adults with a sRV-biV compared to adults with sLV matched for clinical characteristics and systemic ventricular function? Methods: A retrospective cross-sectional comparison of exercise stress test results was performed comparing 24 adults with sRV-biV to 24 adults with a sLV matched for sex (4 females), age (sRV-biV: 46 ± 9 years, sLV: 46 ± 11 years), body mass index (sRV-biV: 28 ± 4 kg/m 2 , sLV: 27 ± 4 kg/m 2 ), ejection fraction of the systemic ventricle (normal: 2, mild: 4, moderate: 11, severe: 7), NYHA class (I: 6, II: 17, III: 1), and doses of diuretics (spironolactone ≤ 25 mg: 24, furosemide ≤ 80 mg: 24 ). Peak VO 2 was compared between groups with Wilcoxon signed-rank tests. Effect sizes are reported as Cohen’s d . Results: Peak VO 2 did not differ significantly between groups (sRV-biV: 20.3 ± 4.2 vs. sLV: 20.9 ± 6.0 mL/kg/min, p=0.43, d =0.18). When patients were dichotomized according to the Weber criterion for optimal versus suboptimal CRF (sLV peak VO 2 > or ≤ 20 mL/kg/min), peak VO 2 was lower in sRV-biV in those with optimal CRF (sRV-biV: 21.0 ± 4.8 vs sLV: 26.6 ± 5.1 mL/kg/min, p=0.006, d =0.72). In contrast, peak VO 2 was greater in sRV-biV in those with suboptimal CRF (sRV-biV: 19.3 ± 3.5 vs. sLV: 16.9 ± 2.0 mL/kg/min, p=0.12, d =NA). Conclusion: Although peak VO 2 values are similar among patients with a sRV-biV and matched controls with a sLV, differences are observed when stratified according to the Weber criteria for optimal CRF. These results may reflect different pathophysiological adaptive mechanisms of a sRV vs sLV. Further studies are required to establish specific prognostic thresholds for patients with sRV-biV.
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