177 High resolution free-breathing automated quantitative myocardial perfusion by cardiovascular magnetic resonance can detect functionally significant coronary artery disease

Background Assessment of myocardial ischaemia from stress perfusion cardiovascular magnetic resonance (SP-CMR) is largely dependent on visual interpretation, with high level operator experience necessary for accurate assessment. Automated SP-CMR perfusion mapping techniques can provide estimation of myocardial blood flow (MBF). This study investigated the use of novel high spatial-resolution free-breathing SP-CMR with automated quantitative mapping in the diagnosis of coronary artery disease (CAD). Diagnostic performance was evaluated against invasive coronary angiography (ICA) with fractional flow reserve (FFR) measurement. Methods Seven-hundred and three patients were recruited for SP-CMR using the research sequence at 3 Tesla. Of those receiving ICA within 6 months, 60 patients had FFR measurement. Those with FFR value ≤ 0.80 were classified as having functionally significant CAD. All patients were imaged during vasodilatory hyperaemia in 3 ventricular slices (basal, mid, apical) with dual-sequence acquisition to calculate the arterial input function. Myocardial blood flow (MBF) maps were automatically generated in-line on the scanner following image acquisition at hyperaemic stress and rest, allowing myocardial perfusion reserve (MPR) calculation. MBF maps were analysed using 600 data points per slice, allowing analysis of the endocardial (inner 50%) and epicardial (outer 50%) myocardial layers. Non-parametric statistical analysis was performed using Mann-Whitney U testing and ROC analysis. Results Seventy-five coronary vessels assessed by FFR were evaluated at both segmental and coronary territory level. The baseline demographics are shown in table 1. Coronary territory stress MBF and MPR were reduced in FFR-positive (≤ 0.80) regions (median stress MBF: 1.74 [0.90–2.17] ml/min/g; MPR: 1.67 [1.10–1.89]) compared with FFR-negative (> 0.80) regions (stress MBF: 2.50 [2.15–2.95] ml/min/g; MPR 2.35 [2.06–2.54] p < 0.001 for both) [figure 1]. When only analysing the lowest 2 segments of each coronary territory, perfusion values were lower in FFR-positive territories (FFR ≤ 0.80: stress MBF 1.53 [0.79–1.90] ml/min/g, MPR 1.42 [0.99–1.78]; FFR > 0.80: stress MBF 2.08 [1.87–2.52] ml/min/g, MPR 2.11 [1.86–2.45], p < 0.001 for both). A similar pattern is seen when assessing the endocardial layers of each coronary territory (FFR ≤ 0.80: stress MBF 1.63 [0.86–2.03] ml/min/g, MPR 1.63 [1.08–1.87]; FFR > 0.80: stress MBF 2.32 [2.00–2.92] ml/min/g, MPR 2.14 [1.92–2.49], p < 0.001 for both). Considering whole territory analysis, stress MBF ≤ 1.94 ml/min/g and MPR ≤ 1.97 accurately detected FFR-positive CAD on a per-vessel basis (area under the curve: 0.85 and 0.96 respectively; p < 0.001 for both). For whole territory analysis: stress MBF sensitivity 70.0%, specificity 90.8%; MPR sensitivity 90.0%, specificity 84.9%. Similar diagnostic performance is seen for both 'lowest 2 segments' and 'endocardial' assessment methods, with higher sensitivity and lower specificity seen for both alternative analyses [figure 2]. Conclusion Scanner-integrated high-resolution free-breathing SP-CMR with automated in-line perfusion mapping can accurately detect functionally significant CAD. High-resolution MBF maps allow assessment of both transmural myocardial segments and the endocardial layers within each coronary territory. Conflict of Interest None