Association between fractional flow reserve and CMR-derived exercise capacity

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NMRC Open-Fund Young Individual Research Grant, Singapore. NMRC Open-Fund Individual Research Grant, Singapore. Background In-scanner exercise stress cardiac magnetic resonance (ExCMR) imaging using supine cycling ergometer offers assessment of perfusion defects, inducible regional wall motion abnormalities, viability and exercise capacity in a single examination (EMPIRE Trial). Aim We aim to investigate the role of CMR-derived exercise capacity to assess the physiological stenosis severity, measured by invasive fractional flow reserve (FFR). Methods 107 patients (60±8 years, 80 males) with suspected coronary artery disease (CAD) underwent ExCMR (Siemens 1.5T) and invasive coronary angiogram with FFR measurement (PressureWireTMX Guidewire – Abbott Laboratories) followed previously published trial protocol [1]. Exercise capacity was derived as age- and sex-specific percentile of peak cardiac index, according to the reference range previously established [2]. Results Exercise capacity remains the only predictor of FFR values (beta 0.005, P<0.001) with backward multivariate regression of clinical variables (age, sex, BMI, presence of hyperlipidema, blood pressure, presence of diabetes mellitus) and quantitative CMR parameters (LV mass, extracellular volume, LV stroke volume at rest and exercise capacity). Patients with haemodynamically significant CAD (FFR<0.8) had significantly lower exercise capacity (median 14 [IQR 4–20] vs 5 [IQR 1–10] age- and sex-specific percentile of peak cardiac index, P<0.001) Conclusion In addition to perfusion defects, regional wall motion abnormalities and viability assessment to detect coronary artery disease, exercise capacity predicts the physiological stenosis severity.