MRI using a combination of intravascular and extracellular contrast media can distinguish between acute myocardial infarction (MI) and chronic infarctions or scars.

NEW YORK (Reuters Health) - MRI using a combination of intravascular and extracellular contrast media can distinguish between acute myocardial infarction (MI) and chronic infarctions or scars, according to a report in the November 21st issue of the Journal of the American College of Cardiology.

Standard extracellular gadolinium (Gd)-chelates contrast enhancement cannot distinguish acute from chronic MI, the authors explain, but intravascular Gd-chelates may produce delayed contrast enhancement of acute but not old MI.

Dr. Maythem Saeed from the University of California, San Francisco, and colleagues examined the potential of intravascular Gd-chelates in discriminating acute from chronic MI in an animal model of 3-day-old and 8-week-old MI.

All acutely infarcted hearts showed delayed enhancement after administration of intravascular and extracellular Gd-chelates, the authors report. In contrast, intravascular Gd-chelate failed to enhance chronic infarctions.

Neither intravascular nor extracellular administration of Gd-chelate caused significant changes in blood pressure or arterial oxygen saturation in either the acute or chronic infarction setting, the researchers note.

"The capability of distinguishing acute MIs from scar tissue by intravascular Gd-chelate might be useful for excluding: 1) a new acute infarction in the clinical setting of known prior infarction or in the presence of ischemic cardiomyopathy, and 2) intraoperative or postoperative infarction in a patient with known prior infarction after revascularization," the investigators suggest.

"If there is no delayed enhancement after administration of intravascular Gd-chelates, it is not an acute infarction," the authors conclude. "Standard extracellular agents would also be preferable for discriminating nonviable from stunning and hibernating myocardium in cases of ischemic cardiomyopathy."

J Am Coll Cardiol 2006;48:1961-1968.