Retrospective Determination of the Area at Risk for Reperfused Acute Myocardial Infarction With T2-Weighted Cardiac Magnetic Resonance Imaging

Abstract

Background-The aim of this study was to determine whether edema imaging by T2-weighted cardiac magnetic resonance (CMR) imaging could retrospectively delineate the area at risk in reperfused myocardial infarction. We hypothesized that the size of the area at risk during a transient occlusion would be similar to the T2-weighted hyperintense region observed 2 days later, that the T2-weighted hyperintense myocardium would show partial functional recovery after 2 months, and that the T2 abnormality would resolve over 2 months. Methods and Results-Seventeen dogs underwent a 90-minute coronary artery occlusion, followed by reperfusion. The area at risk, as measured with microspheres (9 animals), was comparable to the size of the hyperintense zone on T2-weighted images 2 days later (43.4Ϯ3.3% versus 43.0Ϯ3.4% of the left ventricle; PϭNS), and the 2 measures correlated (Rϭ0.84). The infarcted zone was significantly smaller (23.1Ϯ3.7; both PϽ0.001). To test whether the hyperintense myocardium would exhibit partial functional recovery over time, 8 animals were imaged on day 2 and 2 months later. Systolic strain was mapped with displacement encoding with stimulated echoes. Edema, as detected by a hyperintense zone on T2-weighted images, resolved, and regional radial systolic strain partially improved from 4.9Ϯ0.7 to 13.1Ϯ1.5 (Pϭ0.001) over 2 months. Conclusions-These findings are consistent with the premise that the T2 abnormality depicts the area at risk, a zone of reversibly and irreversibly injured myocardium associated with reperfused subendocardial infarctions. The persistence of postischemic edema allows T2-weighted CMR to delineate the area at risk 2 days after reperfused myocardial infarction.

Non-contrast T1-mapping detects acute myocardial edema with high diagnostic accuracy: a comparison to T2-weighted cardiovascular magnetic resonance

“…The “gold standard” for defining myocardial edema on imaging, however, is controversial [22]. Experimental animal models using fluorescent microspheres to delineate myocardium area-at-risk in acute MI correlated to T2w-CMR imaging [4]; however, topographic correlation between T2w images and histopathological validation of pure myocardial edema without infarction in humans is lacking, largely due to the difficulty in accurately measuring edema in histopathological samples. We thus decided to study patients presenting with cardiac conditions known to involve acute edema but without co-existing infarction or other pathology detected by LGE.…”

“…It is used for differentiation of acute from chronic MI [2], assessment of the area-at-risk [3,4], myocarditis [5] and increasingly as a surrogate end-point in clinical trials [6]. …”

Left Ventricular Hypertrophy Is Associated With Increased Infarct Size and Decreased Myocardial Salvage in Patients With ST‐Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

“…Although reasons are well described and patients were recruited on a consecutive basis, these dropouts may represent a risk of selection bias, given that the clinical condition is likely to correlate with infarct size and/or LVEF. Third, area at risk was evaluated using a T 2 ‐weighted CMR technique, which has been validated against histopathologically defined area at risk 19. Myocardial salvage assessed by CMR has also been shown to be a reproducible tool with excellent agreement with single‐photon emission computed tomography and angiography 18, 41.…”

“…Cardiovascular magnetic resonance (CMR) provides an accurate method for in vivo assessment of infarct size,14, 15 area at risk,16, 17, 18, 19 myocardial salvage index,20, 21 MVO,22 LV mass, and LV ejection fraction (LVEF) 23…”

In vivo chronic myocardial infarction characterization by spin locked cardiovascular magnetic resonance

“…T2-weighted CMR has been observed to overestimate the size of MI compared to LGE in acute MI [22]. This has prompted further research to understand T2-weighted enhancement as an area at risk rather than the infarct scar size alone [27]. Therefore a measurable difference between T2-weighted and LGE would enable the evaluation of interventional procedures to reduce infarct size from the initial area at risk.…”