Performance of CMR Methods for Differentiating Acute From Chronic MI

AbstractObjectivesThe purpose of this study was to assess the performance of cardiac magnetic resonance (CMR) methods for discriminating acute from chronic myocardial infarction (MI).BackgroundAlthough T2-weighted CMR is thought to be accurate in differentiating acute from chronic MI, few studies have reported on diagnostic accuracy, and these generally compared extremes in infarct age (e.g., <1 week old vs. more than 6 months old) and did not evaluate other CMR methods that could be informative.MethodsA total of 221 CMR studies were performed at various time points after ST-segment elevation myocardial infarction in 117 consecutive patients without a history of MI or revascularization enrolled prospectively at 2 centers. Imaging markers of acute MI (<1 month) were T2 hyperintensity on double inversion recovery turbo spin echo (DIR-TSE) images, microvascular obstruction (MO) on delayed-enhancement CMR, and focally increased end-diastolic wall thickness (EDWT) on cine-CMR.ResultsThe prevalence of T2-DIR-TSE hyperintensity decreased with infarct age but remained substantial up to 6 months post-MI. In contrast, the prevalence of both MO and increased EDWT dropped sharply after 1 month. T2-DIR-TSE sensitivity, specificity, and accuracy for identifying acute MI were 88%, 66%, and 77% compared with 73%, 97%, and 85%, respectively, for the combination of MO or increased EDWT. On multivariable analysis, persistence of T2-hyperintensity in intermediate-age infarcts (1 to 6 months old) was predicted by larger infarct size, diabetes, and better T2-DIR-TSE image quality score. For infarct size ≥10% of the left ventricle, a simple algorithm incorporating all CMR components allowed classification of infarct age into 3 categories (<1 month old, 1 to 6 months old, and ≥6 months old) with 80% (95% confidence interval: 73% to 87%) accuracy.ConclusionsT2-DIR-TSE hyperintensity is specific for infarcts <6 months old, whereas MO and increased EDWT are specific for infarcts <1 month old. Incorporating multiple CMR markers of acute MI and their varied longevity leads to a more precise assessment of infarct age

Identifying the Infarct-Related Artery in Patients With Non–ST-Segment–Elevation Myocardial Infarction

BACKGROUND: Determining the infarct-related artery (IRA) in non-ST-segment-elevation myocardial infarction (MI) can be challenging. Delayed-enhancement cardiac magnetic resonance (DE-CMR) can accurately identify small MIs. The purpose of this study was to determine whether DE-CMR improves the ability to identify the IRA in patients with non-ST-segment-elevation MI. METHODS AND RESULTS: In this 3-center, prospective study, we enrolled 114 patients presenting with their first MI. Patients underwent DE-CMR followed by coronary angiography. The interventional cardiologist was blinded to the DE-CMR results. Later, coronary angiography and DE-CMR images were reviewed independently and blindly for identification of the IRA. The pattern of DE-CMR hyperenhancement was also used to determine whether there was a nonischemic pathogenesis for myocardial necrosis. The IRA was not identifiable by coronary angiography in 37% of patients (n=42). In these, the IRA or a new noncoronary artery disease diagnosis was identified by DE-CMR in 60% and 19% of patients, respectively. Even in patients with an IRA determined by coronary angiography, a different IRA or a noncoronary artery disease diagnosis was identified by DE-CMR in 14% and 13%, respectively. Overall, DE-CMR led to a new IRA diagnosis in 31%, a diagnosis of nonischemic pathogenesis in 15%, or either in 46% (95% CI, 37%-55%) of patients. Of 55 patients undergoing revascularization, 27% had revascularization solely to nonculprit coronary artery territories as determined by DE-CMR. CONCLUSIONS: Identification of the IRA by coronary angiography can be challenging in patients with non-ST-segment-elevation MI. In nearly half, DE-CMR may lead to a new IRA diagnosis or elucidate a nonischemic pathogenesis. Revascularization solely of coronary arteries that are believed to be nonculprit arteries by DE-CMR is not uncommon