2-052 Coronary microvascular resistance as a predictor of the placebo-controlled response to percutaneous coronary intervention in stable single-vessel coronary artery diseaseMicrovascular-Stratified Analysis of ORBITA

Introduction No data describing the relationship between hyperaemic coronary microvascular resistance (hMVR) with the placebo-controlled effect of percutaneous coronary intervention (PCI) in stable coronary artery disease exist. Methods Patients with severe single-vessel coronary artery disease, optimally treated with anti-anginal medication, from the ORBITA trial (Objective Randomised Blinded Investigation With Optimal Medical Therapy of Angioplasty in Stable Angina) were included. Hyperaemic MVR was calculated computationally by blinded operators and compared against placebo-controlled changes in treadmill exercise time, patient-reported symptoms, physician-assessed symptoms and dobutamine stress echocardiography scores using Bayesian regression modelling. Results Hyperaemic MVR was computed for 131 patients (66 PCI and 65 placebo). Median hMVR was 1.38 [0.89 – 2.09] mmHg.min/mL. Baseline exercise time correlated with hMVR (ordinal correlation coefficient=0.20, 95% Credible Interval (CrI) 0.18 to 0.22). For patients with low (20th centile) hMVR, PCI increased exercise time by 48 seconds versus placebo (95% CrI 6 to 92 seconds, probability of significant difference (Pr)=98.5%). Exercise time did not improve for patients with high (80th centile) hMVR (16 seconds, 95% CrI -29 to 61, Pr=75.2%). Effect of this interaction was modest (Printeraction=83.1%). Low hMVR also predicted a placebo-controlled benefit of PCI for likelihood of complete freedom from angina (Pr=98.8%) and improvements in angina frequency (Pr=97.8%) and stress echocardiography scores (Pr=99.9%). Conclusions Low hMVR was associated with a placebo-controlled benefit of PCI for several patient-centred outcomes and stress echocardiography scores. For patients with severe single vessel disease, taking optimal medical therapy, coronary microvascular dysfunction may attenuate functional and symptomatic benefits of PCI.