title: Microvascular injury in reperfused infarcted myocardium: noninvasive assessment with contrast-enhanced echoplanar magnetic resonance imaging.
abstract: OBJECTIVE
  The purpose of this study was to measure the accumulation of labeled albumin and to visualize its distribution pattern in reperfused infarcted myocardium as a function of time between onset of reperfusion and administration of the tracer.
  
  
  BACKGROUND
  Myocardial microvascular injury leads to leakage of albumin from the intravascular space. Quantitative measurements of GdDTPA-albumin with inversion recovery echoplanar imaging (IR-EPI) may allow noninvasive monitoring of microvascular injury.
  
  
  METHODS
  After 1 h of coronary artery occlusion, 56 rats were injected with GdDTPA-albumin or 123I-GdDTPA-albumin either immediately before reperfusion or 1/2, 1 or 24 h after reperfusion. GdDTPA-albumin in blood, normal myocardium and reperfused infarction was dynamically measured with IR-EPI during 1 h postinjection (PI). Autoradiograms were obtained at 15 min PI. Accumulation of labeled albumin in myocardium was expressed as the ratio of myocardial to blood content.
  
  
  RESULTS
  In normal myocardium, the ratio of changes of relaxation rate-ratio (deltaR1-ratio) was 0.12+/-0.01 and did not change over 1 h. In reperfused infarction, however, the deltaR1-ratio increased after administration. Animals given GdDTPA-albumin before reperfusion exhibited fastest accumulation (deltaR1-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 (deltaR1-ratios 15 min PI: 0.39+/-0.03; 0.31+/-0.04; 0.16+/-0.01; p < 0.001 compared to administration before reperfusion). Moreover, the tracer accumulated predominantly in the periphery of the injury zone.
  
  
  CONCLUSIONS
  Amount and distribution pattern of labeled albumin in reperfused infarction are modulated by duration of reperfusion. The accumulation of GdDTPA-albumin can be quantified by IR-EPI. Thus, IR-EPI may be useful to noninvasively monitor myocardial microvascular injury in reperfused infarction.
authors.affiliation: Department of Radiology, University of California San Francisco, 94143-0628, USA.
authors.forename: J
authors.initials: J
authors.lastname: Bremerich
authors.forename: M F
authors.initials: MF
authors.lastname: Wendland
authors.forename: H
authors.initials: H
authors.lastname: Arheden
authors.forename: R
authors.initials: R
authors.lastname: Wyttenbach
authors.forename: D W
authors.initials: DW
authors.lastname: Gao
authors.forename: J P
authors.initials: JP
authors.lastname: Huberty
authors.forename: M W
authors.initials: MW
authors.lastname: Dae
authors.forename: C B
authors.initials: CB
authors.lastname: Higgins
authors.forename: M
authors.initials: M
authors.lastname: Saeed
mesh_terms: D000418:Albumins; D000818:Animals; D001810:Blood Volume / Q000502:physiology; D003287:Contrast Media; D003331:Coronary Vessels / Q000473:pathology; D017352:Echo-Planar Imaging; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D008833:Microcirculation / Q000473:pathology; D009203:Myocardial Infarction / Q000175:diagnosis*; D015428:Myocardial Reperfusion Injury / Q000175:diagnosis*; D009206:Myocardium / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000418:Albumins; D003287:Contrast Media; C058946:albumin-(gadolinium-DTPA); D019786:Gadolinium DTPA