title: Scarred myocardium imposes additional burden on remote viable myocardium despite a reduction in the extent of area with late contrast MR enhancement.
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.
authors.affiliation: Department of Radiology, University of California, San Francisco, 94143-0628, USA. Maythem.Saeed@radiology.ucsf.edu
authors.forename: Maythem
authors.initials: M
authors.lastname: Saeed
authors.forename: Randall J
authors.initials: RJ
authors.lastname: Lee
authors.forename: Oliver
authors.initials: O
authors.lastname: Weber
authors.forename: Loi
authors.initials: L
authors.lastname: Do
authors.forename: Alastair
authors.initials: A
authors.lastname: Martin
authors.forename: Philip
authors.initials: P
authors.lastname: Ursell
authors.forename: David
authors.initials: D
authors.lastname: Saloner
authors.forename: Charles B
authors.initials: CB
authors.lastname: Higgins
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage; D006571:Heterocyclic Compounds / Q000008:administration & dosage; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009203:Myocardial Infarction / Q000473:pathology*; D009206:Myocardium / Q000473:pathology*; D009942:Organometallic Compounds / Q000008:administration & dosage; D013194:Staining and Labeling; D013552:Swine
chemical_list: D003287:Contrast Media; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; C050823:gadolinium 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetate