Reversible and irreversible injury in the reperfused myocardium: differentiation with contrast material-enhanced MR...

Thrombolytic agents are being used with increasing frequency to produce reperfusion of acute myocardial infarction in humans. This study was designed to assess the potential of a magnetic resonance (MR) contrast agent, the manganese chelate of N,N'-bis(pyridoxal-5-phosphate) ethylenediamine-N,N'-diacetic acid (DPDP), in differentiating between reversible and irreversible myocardial injury during reperfusion. Ischemia was produced in rats by occlusion of the left coronary artery for either 15 minutes (n = 10) or 2 hours (n = 10), followed in both cases by 30 minutes of reperfusion. Signal intensity (SI) was measured before and after (every 15 minutes for 1 hour) the administration of Mn-DPDP. Prior to intravenous injection of the contrast agent, no significant difference in SI was observed between normal and reversibly or irreversibly injured myocardium. Mn-DPDP produced greater enhancement of SI of the irreversibly injured region compared with normal myocardium. There was no differential enhancement of the reversibly injured region compared with normal myocardium. Thus, Mn-DPDP is useful in discriminating reversible from irreversible injury in reperfused myocardium.