Abstract 13116: Ventilatory Gas Exchange in Stable Coronary Artery Disease

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.