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Introduction: Improvement in exercise capacity is a therapeutic goal of percutaneous coronary intervention (PCI) for stable coronary artery disease (CAD). Cardiopulmonary exercise testing (CPET) provides an accurate quantification of cardio-respiratory fitness through analysis of ventilatory gas exchange (VGE). The aim of this secondary analysis from the ORBITA trial is to determine the placebo-controlled effect of PCI on VGE parameters and determine if pre-randomisation exercise capacity predicts the placebo-controlled efficacy of PCI. Methods: Following a 6-week medication optimisation phase, patients with severe single vessel CAD underwent pre-randomisation treadmill CPET using the smoothed modified Bruce protocol. Patients were then randomly assigned to PCI or a placebo procedure. At the end of the 6-week follow up period, patients underwent repeat CPET before being unblinded to treatment allocation. Results: CPET data was available for 195 patients (mean age 66.1 ± 9.1, 73.3% male). At baseline, peak oxygen uptake (VO 2 ) was 21.5±6.7ml/kg/min in the PCI arm (n=102) and 20.6±6.6ml/kg/min in the placebo arm (n=93). At follow up, there was no significant benefit from PCI over a placebo procedure for any ventilatory gas exchange (peak VO 2 , p=0.826; O 2 -pulse plateau, p=0.638) or haemodynamic parameter (rate-pressure product, p=0.215). Although PCI resulted in significantly improved patient-reported freedom from angina (OR, 2.58 [95% CI, 1.35-14.92] p=0.004) and angina frequency score (OR, 1.73 [95% CI, 1.02 to 2.96], p=0.0432), there was no detectable interaction between peak VO 2 and these endpoints (P interaction(int) =0.715 and P int =0.588 respectively). Similarly, pre-randomisation peak VO 2 did not predict the placebo-controlled benefit of PCI on physical limitation (P int =0.293), quality of life (P int =0.380), EuroQOL 5 visual analogue score (P int =0.695), Canadian Cardiovascular Society angina class (P int =0.120) or exercise time (P int =0.897). Conclusions: When assessed against placebo, PCI does not improve VGE or exercise capacity, assessed by CPET. Furthermore, pre-randomisation exercise capacity does not predict the placebo-controlled effect of PCI on symptom relief, even in patients with lower functional capacity.

Introduction: Cardiopulmonary exercise testing (CPET) provides a non-invasive evaluation of exercise physiology via ventilatory gas exchange (VGE). We do not know how these assessments correlate with myocardial ischemia or angina symptoms in patients with stable single-vessel coronary artery disease (CAD). In this analysis, we use randomised, blinded data from the ORBITA trial to investigate the association between VGE, ischemia and symptoms in patients with severe single-vessel CAD. Methods: Patients underwent treadmill CPET using the smoothed-modified Bruce protocol, after a 6-week medical optimisation phase during which antianginals were uptitrated. Symptoms were assessed using the Seattle Angina Questionnaire (SAQ), EuroQOL 5 and Canadian Cardiovascular Society (CCS) angina class. Ischemia was quantified using fractional flow reserve (FFR), instantaneous wave-free ratio (iFR) and dobutamine stress echocardiography (DSE). Results: We assessed 195 patients [mean age 66.1±9.1, 143 (73.3%) male]. We found a significant association between peak oxygen uptake (VO 2 ) and minute ventilation to carbon dioxide (VE/VCO 2 ) slope, and physician assessed CCS class [P correlation(cor) cor cor cor cor cor =0.0001) and EuroQOL 5 visual analogue score (P cor = 0.0011, P cor =0.0019). There was no detectable relationship between peak VO 2 or VE/VCO 2 slope, and FFR, iFR or DSE (p>0.05, for all). Patients with an oxygen pulse plateau however, had higher dobutamine stress echo score compared to those without (+0.71; 95%CI 0.22-1.21, p=0.0049). Conclusions: The association between VGE and angina symptoms is stronger than its ability to detect severity of myocardial ischemia. This analysis highlights the complexity of the relationship between symptoms, functional capacity and myocardial ischemia.