Myocardial flow reserve measurement in cardiac SPECT: A strong predictor of lesions at invasive coronary angiography

Abstract

Myocardial flow reserve (MFR) measurement is predictive of major adverse cardiovascular (CV) events (MACE) and has been shown to improve diagnostic performances of coronary artery disease (CAD) in cardiac positron emission tomography. MFR can now be assessed during dynamic myocardial perfusion imaging (MPI) in SPECT, but its correlation with the patient's risk of coronary artery disease (CAD) remains to be investigated. We evaluated the results of SPECT MFR measurement in patients referred for CAD screening. In total, 137 patients (61 male, 76 female) referred for CAD screening MPI between November 2018 and March 2020 were included in a prospective trial (CFR-OR). 10 years risk of cardiovascular death according to the European Society of Cardiology (SCORE) was calculated. SPECT data were acquired on a CZT-cardiac camera using a stress/rest one-day Tc-99m-tetrofosmin protocol. Low dose thoracic CT was used for coronary calcium score (CCS) evaluation. Invasive Coronary Angiography (ICA) was performed upon decision of the referring cardiologist. Mean SCORE was 4 ± 3.1%. Mean global MFR was 2.50 ± 0.74. There was a significant inverse correlation between MFR and SCORE ( P = 0.006), gender ( P = 0.019), and the number of cardiovascular risk factors ( P = 0.01). MFR was significantly reduced in patients with CCS above 1 ( P = 0.01). Twenty-three patients underwent ICA. Eighteen showed coronary plaques qualifying for high-risk patients; among them, 16 patients had impaired MFR (the 2 other patients had moderate stenosis, < 50%, with negative FFR), whereas only 4 had abnormal visual MPI. Based on global MFR, and with a threshold of 2, sensitivity and specificity were respectively 83.3% and 100%, and Area Under Curve (AUC) was 0.94. Global MFR measured during MPI SPECT for CAD screening may contribute to high-risk patient identification. It significantly enhances SPECT diagnostic performances and could help physician decision to perform ICA.