Aims
Oxygen-pulse morphology and gas exchange analysis measured during cardiopulmonary exercise testing (CPET) has been associated with myocardial ischaemia. We examine the relationship between CPET parameters, myocardial ischaemia and anginal symptoms in patients with chronic coronary syndrome. We also determine the ability of these parameters to predict the placebo-controlled response to percutaneous coronary intervention (PCI).
Methods and results
Patients with severe single vessel coronary artery disease were randomised 1:1 to PCI or placebo in the ORBITA trial. Subjects underwent pre-randomisation treadmill CPET, dobutamine stress-echocardiography (DSE) and symptom assessment. These assessments were repeated at the end of a 6-week blinded follow-up period.

195 patients with CPET data were randomised (102 PCI, 93 placebo). Patients in whom an oxygen-pulse plateau was observed during CPET had higher (more ischaemic) DSE score (+0.82 segments; 95%CI, 0.40 to 1.25, P=0.0068) and lower FFR (-0.07; -0.12 to -0.02, P=0.011) compared to those without. At lower (more abnormal) oxygen-pulse slopes, there was a larger improvement of the placebo-controlled effect of PCI on DSE score (oxygen-pulse plateau presence [Pinteraction=0.026] and oxygen-pulse gradient [Pinteraction=0.023]) and Seattle angina physical-limitation score (oxygen-pulse plateau presence [Pinteraction=0.037]). Impaired peak VO2, VE/VCO2 slope, peak oxygen-pulse and oxygen-uptake efficacy slope was significantly associated with higher symptom burden but did not relate to severity of ischaemia or predict response to PCI.

Conclusion
Although selected CPET parameters relate to severity of angina symptoms and quality of life, only an oxygen-pulse plateau detects the severity of myocardial ischaemia and predicts the placebo-controlled efficacy of PCI in patients with single-vessel coronary artery disease.