MICROVASCULAR INJURY IN REPERFUSED INFARCTED MYOCARDIUM - NONINVASIVEASSESSMENT WITH CONTRAST-ENHANCED ECHOPLANAR MAGNETIC-RESONANCE-IMAGING

Objectives. The purpose of this study was to measure the accumulation of labeled albumin and to visualize its distribution pattern in reperf used infarcted myocardium as a function of time between onset of reper fusion and administration of the tracer. Background. Myocardial microv ascular injury leads to leakage of albumin from the intravascular spac e. Quantitative measurements of GdDTPA-albumin with inversion recovery echoplanar imaging (IR-EPI) may allow noninvasive monitoring of micro vascular injury. Methods. After 1 h of coronary artery occlusion, 56 r ats were injected with GdDTPA-albumin or I-123-GdDTPA-albumin either i mmediately before reperfusion or 1/2, 1 or 24 h after reperfusion. GdD TPA-albumin in blood, normal myocardium and reperfused infarction was dynamically measured with IR-EPI during 1 h postinjection (PI). Autora diograms were obtained at 15 min PI. Accumulation of labeled albumin i n myocardium was expressed as the ratio of myocardial to blood content . Results. In normal myocardium, the ratio of changes of relaxation ra te-ratio (Delta R1-ratio) was 0.12 +/- 0.01 and did not change over 1 h. Tn reperfused infarction, however, the Delta R1-ratio increased aft er administration. Animals given GdDTPA-albumin before reperfusion exh ibited fastest accumulation (Delta R1-ratio 15 min PI: 0.56 +/- 0.03) and essentially homogeneous distribution, The accumulation was slower when administered at 1/2, 1 and 24 h after reperfusion (Delta R1-ratio s 15 min PI: 0.39 +/- 0.03; 0.31 +/- 0.04; 0.16 +/- 0.01; p < 0.001 co mpared to administration before reperfusion). Moreover, the tracer acc umulated predominantly in the periphery of the injury zone. Conclusion s. Amount and distribution pattern of labeled albumin in reperfused in farction are modulated by duration of reperfusion. The accumulation of GdDTPA-albumin can be quantified by IR-EPI. Thus, IR-EPI may be usefu l to noninvasively monitor myocardial microvascular injury in reperfus ed infarction. (J Am Coll Cardiol 1998;32:787-93) (C)1998 by the Ameri can College of Cardiology.