Abstract
<h3>Objective</h3> Cardiopulmonary exercise testing (CPET) is non-invasive and safe, reliable and reproducible and has been robustly demonstrated to be linked to clinical end-points such as hospitalisation and death. CPET provides objective information on exercise capacity. However in practice, CPET data can be difficult to interpret. We examined the validity of standard CPET parameters in patients with atrial fibrillation (AF). <h3>Methods and results</h3> Standard CPETs were prospectively performed in 69 patients (mean age 64) with paroxysmal AF. The ratio of ventilation to carbon dioxide elimination (VE/VCO2) measured at the ventilatory threshold (VT) correlated with VE/VCO2 across the test (r = 0.84, p < 0.001) and at its nadir (rho = 0.92, p < 0.001). Peak end-tidal carbon dioxide (ETCO2) correlated well with ETCO2 at peak exertion (r = 0.88, p < 0.001) and at rest (r = 0.68, p < 0.001). However, absolute VE/VCO2 and ETCO2 values were significantly different with different measurement methods. Unadjusted peak oxygen uptake (VO2) correlated with VO2 at the VT (rho = 0.94, p < 0.001), and oxygen uptake efficiency slope (OUES; rho = 0.92, p < 0.001). However, once OUES and VO2peak were indexed against standard reference ranges, they had a lower level of agreement (rho = 0.78, p < 0.001). Alternative formulae for predicting VO2peak returned markedly different results. In 34 of 69 (49%) of patients, the% predicted VO2peak appeared above normal (>100% predicted) in one reference range, but abnormal (<84% predicted) in another. <h3>Conclusions</h3> In patients with paroxysmal AF, CPET data were sufficiently consistent that peak exercise capacity could be predicted from submaximal measures. However, in this population, reference ranges for VO2peak were markedly inconsistent. Adjusted values for VO2peak and OUES should be interpreted with caution in these patients.
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