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

TLDR

The study aimed to determine whether T2‑weighted cardiac MRI could retrospectively delineate the area at risk in reperfused myocardial infarction and to test if its size matched the hyperintense zone, if the zone showed functional recovery after two months, and if the abnormality resolved over time. Seventeen dogs underwent a 90‑minute coronary occlusion followed by reperfusion, with eight animals imaged on day 2 and at 2 months using displacement‑encoding echo techniques to map systolic strain. T2‑weighted hyperintensity measured 2 days post‑reperfusion matched the microsphere‑determined area at risk (≈43 % of the LV), the infarct zone.

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 (43.4±3.3% versus 43.0±3.4% of the left ventricle; P =NS), and the 2 measures correlated ( R =0.84). The infarcted zone was significantly smaller (23.1±3.7; both P <0.001). 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 4.9±0.7 to 13.1±1.5 ( P =0.001) 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.