A hypointense core of infarcted myocardium in T2-weighted cardiovascular MRI (CMR) has been used as a noninvasive marker for intramyocardial hemorrhage. However, the clinical significance of such findings not yet been established. The aim of this study was to evaluate determinants and prognostic impact of a hypointense infarct core in T2-weighted CMR images, studied in patients after acute, reperfused ST-elevation–myocardial infarction.

We analyzed 346 patients with ST-elevation–myocardial infarction undergoing primary angioplasty <12 hours after symptoms onset. T2-weighted, contrast-enhanced CMR was used for assessment of the area at risk, myocardial salvage, infarct size, hypointense core in T2-weighted images, and late microvascular obstruction. Patients were categorized into 2 groups defined by the presence or absence of a hypointense core. The primary end point of the study was occurrence of major adverse cardiovascular events defined as death, reinfarction, and congestive heart failure within 6 months after infarction. A hypointense core was present in 122 (35%) patients and was associated with larger infarcts, greater amount of microvascular obstruction, less myocardial salvage, and impaired left ventricular function (P<0.001, respectively). The presence of a hypointense core was a strong univariable predictor of major adverse cardiovascular events (hazard ratio, 2.59; confidence interval, 1.27 to 5.27) and was significantly associated with an increased major adverse cardiovascular events rate (16.4% versus 7.0%, P=0.006) 6 months after infarction.

A hypointense infarct core within the area at risk of reperfused infarcted myocardium in T2-weighted CMR is closely related to infarct size, microvascular obstruction, and impaired left ventricular function, with subsequent adverse clinical outcome.