Experimental

European Radiology

, Volume 16, Issue 4, pp 827-836

Scarred myocardium imposes additional burden on remote viable myocardium despite a reduction in the extent of area with late contrast MR enhancement

  • Maythem SaeedAffiliated withDepartment of Radiology, University of California Email author 
  • , Randall J. LeeAffiliated withDepartment of Medicine, University of California
  • , Oliver WeberAffiliated withDepartment of Radiology, University of California
  • , Loi DoAffiliated withDepartment of Radiology, University of California
  • , Alastair MartinAffiliated withDepartment of Radiology, University of California
  • , Philip UrsellAffiliated withDepartment of Pathology, University of California
  • , David SalonerAffiliated withDepartment of Radiology, University of California
  • , Charles B. HigginsAffiliated withDepartment of Radiology, University of California

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Abstract

Magnetic resonance imaging (MRI) can simultaneously detect and quantify myocardial dysfunction and shrinkage in contrast-enhanced areas postinfarction. This ability permits the investigation of our hypothesis that transformation of infracted myocardium to scarred tissue imposes additional burdens on peri-infarcted and remote myocardium. Pigs (n=8) were subjected to reperfused infarction. Gd-DOTA-enhanced inversion recovery gradient echo sequence (IR-GRE) imaging was performed 3 days and 8 weeks postinfarction. Global and regional left ventricular (LV) function was evaluated by cine MRI. Triphenyltetrazolium chloride (TTC) stain was used to delineate infarction while hematoxylin and eosin (H & E) and Masson’s trichrome stains were used to characterize remodeled myocardium. Late contrast-enhanced MRIs showed a decrease in the extent of enhanced areas from 17±2% at 3 days to13±1% LV mass at 8 weeks. TTC infarction size was 12±1% LV mass. Cine MRIs showed expansion in dysfunctional area due to unfavorable remodeling, ischemia, or strain. Ejection fraction was reduced in association with increased end-diastolic and end-systolic volumes. Scarred myocardium contained collagen fibers and remodeled thick-walled vessels embedded in collagen. Sequential MRI showed greater LV dysfunction despite the shrinkage in extent of enhanced areas 2 months postinfarction. The integration of late enhancement and cine MRI incorporates anatomical and functional evaluation of remodeled hearts.

Keywords

Myocardial infarction Cardiac function Magnetic resonance imaging (MRI) MR contrast media Left ventricular remodeling