Temporal and spatial characteristics of the area at risk investigated using computed tomography and T1-weightedmagnetic resonance imaging

Abstract

Aims Cardiovascular magnetic resonance (CMR) imaging can measure the myocardial area at risk (AAR), but the technique has received criticism for inadequate validation. CMR commonly depicts an AAR that is wider than the infarct, which in turn would require a lateral perfusion gradient within the AAR.We investigated the presence of a lateral perfusion gradient within the AAR and validated CMR measures of AAR against three independent reference standards of high quality. Methods and results Computed tomography (CT) perfusion imaging, microsphere blood flow analysis, T1-weighted 3TCMR and fluorescent microparticle pathology were used to investigate the AAR in a canine model (n = 10) of ischaemia and reperfusion. AAR size by CMR correlated well with CT (R2 = 0.80), microsphere blood flow (R2 = 0.80), and pathology (R2 = 0.74) with good limits of agreement [20.79±4.02% of the left ventricular mass (LVM) vs. CT; 21.49±4.04% LVMvs. blood flow and21.01±4.18% LVMvs. pathology]. The lateral portion of theAARhad higher perfusion than the core of theAARby CT perfusion imaging (40.7±11.8 vs. 25.2±17.7 Hounsfield units, P = 0.0008) and microsphere blood flow (0.11±0.04 vs. 0.05±0.02 mL/g/min, lateral vs. core, P = 0.001). The transmural extent of MI was lower in the lateral portion of the AAR than the core (28.2±10.2 vs. 17.4±8.4% of the wall, P = 0.001). Conclusion T1-weightedCMRaccurately quantifies size of theAARwith excellent agreement compared with three independent reference standards. A lateral perfusion gradient results in lower transmural extent of infarction at the edges of the AAR compared with the core.