16 Reliability of fully automated, inline quantitative assessment of myocardial perfusion in patients with suspected coronary artery disease

Introduction Recent developments in the field of myocardial perfusion assessment with cardiovascular magnetic resonance (CMR) enable the automated inline quantification of myocardial blood flow (MBF).1 This offers potential advantages over qualitative assessment of images, providing an objective, quantitative and serially evaluable endpoint. Previous studies have assessed the reliability of quantitative myocardial perfusion assessment by CMR in healthy volunteers only.2 This study assessed the reproducibility of this technique in patients with suspected stable coronary artery disease (CAD). Materials and Methods Patients with suspected CAD were studied with CMR perfusion assessment at 3-Tesla on two separate days. CMR perfusion imaging was performed at rest and during adenosine stress (140–210mcg/kg/min) using a dual-sequence T1-weighted saturation recovery gradient echo sequence acquired over 60 heartbeats, following intravenous injection of 0.075mmol/kg of a gadolinium-based contrast agent (Dotarem) followed by 20ml saline bolus (injection speed 4ml/s). Inline automatic reconstruction and image post-processing were implemented within the Gadgetron software framework, calculating MBF using a blood tissue exchange model, displayed on pixel-wise perfusion maps.1 Perfusion maps were blindly analysed offline by manually tracing endocardial and epicardial contours for each slice, and applying a 10% offset for each border. Segmental MBF was calculated, applying the 16-segment American Heart Association (AHA) model.3Myocardial perfusion reserve (MPR) was defined as the ratio of segmental hyperaemic MBF/rest MBF uncorrected for rate-pressure product. Reliability of global stress and rest MBF, and MPR were evaluated using Bland-Altman plots and intraclass correlation coefficients (ICC).4 Results 61 patients (mean age 67±9 years, 77% male) were studied. The median interval between the two scans was three days. There was no significant interstudy difference in global stress MBF between the two scans (1.52±0.66ml/min/g vs 1.52±0.59mlmin/g, p=0.98), global rest MBF (0.55±0.16ml/min/g vs 0.55±0.16ml/min/g, p=0.99) or global MPR (2.85±1.05 vs 2.85±1.15, p=0.99). Stress MBF, rest MBF and MPR showed intraclass correlations of 0.55 (95%CI 0.35–0.71), 0.58 (95%CI 0.37–0.73) and 0.47 (95%CI 0.23–0.65), respectively (Bland-Altman plots in figure 1). Conclusion In patients with suspected CAD, quantitative assessment of myocardial perfusion by fully automated inline myocardial mapping shows moderate-good reliability for both stress and rest MBF, but poorer correlation with MPR. References Kellman P, Hansen MS, Nielles-Vallespin S, Nickander J, Themudo R, Ugander M, et al. Myocardial perfusion cardiovascular magnetic resonance: optimized dual sequence and reconstruction for quantification. J Cardiovasc Magn Reson. 2017;19(1):43. Brown LAE, Onciul SC, Broadbent DA, Johnson K, Fent GJ, Foley JRJ, et al. Fully automated, inline quantification of myocardial blood flow with cardiovascular magnetic resonance: repeatability of measurements in healthy subjects. J Cardiovasc Magn Reson. 2018;20(1):48. Cerqueira MD, Weissman NJ, Dilsizian V, Jacobs AK, Kaul S, Laskey WK, et al. Standardized myocardial segmentation and nomenclature for tomographic imaging of the heart. A statement for healthcare professionals from the Cardiac Imaging Committee of the Council on Clinical Cardiology of the American Heart Association. Circulation. 2002;105(4):539–42. Altman DG, Bland JM. Measurement in medicine: the analysis of method comparison studies. Journal of the Royal Statistical Society Series D (The Statistician). 1983;32(3):307–17.