PROGNOSTIC-SIGNIFICANCE OF MICROVASCULAR OBSTRUCTION BY MAGNETIC-RESONANCE-IMAGING IN PATIENTS WITH ACUTE MYOCARDIAL-INFARCTION

Background-The extent oi microvascular obstruction during acute corona ry occlusion may determine the eventual magnitude of myocardial damage and thus, patient prognosis after infarction. By contrast-enhanced MR I, regions of profound microvascular obstruction at tile infarct core are hypoenhanced and correspond to greater myocardial damage acutely. We investigated whether profound microvascular obstruction after infar ction pr-edicts 2-year cardiovascular morbidity and mortality. Methods and Results-Forty-four patients underwent MRI 10+/-6 days after infar ction. Microvascular obstruction was defined as hypoenhancement seen 1 to 2 minutes after contrast injection. Infarct size was assessed as p ercent left ventricular mass hyperenhanced 5 to 10 minutes alter contr ast, Patients were followed clinically for 16+/-5 months. Seventeen pa tients returned 6 months after infarction for repeat MRI. Patients wit h microvascular obstruction (n=11) had more cardiovascular events than those without (45% versus 9%; P=.016). In fact, microvascular status predicted occurrence of cardiovascular complications (chi(2)=6.46, P<. 01). The risk of adverse events increased with infarct extent (30%, 43 %, and 71% for small [n=10], midsized [n=14], and large [n=14] infarct s, P<.05). Even after infarct size was controlled for, the presence of microvascular obstruction remained a prognostic marker of postinfarct ion complications (chi(2)=5.17, P<.05). Among those returning for foll ow-up imaging, the presence of microvascular obstruction was associate d with fibrous scar formation (chi(2)=10.0, P<.01) and left ventricula r remodeling (P<.05). Conclusions-After infarction, MRI-determined mic rovascular obstruction predicts more frequent cardiovascular complicat ions, In addition, infarct size determined by MRI also relates directl y to long-term prognosis in patients with acute myocardial infarction. Moreover, microvascular status remains a strong prognostic marker eve n after control for infarct size.