Discrimination of myocardial acute and chronic (scar) infarctions on delayed contrast enhanced magnetic resonance imaging with intravascular magnetic resonance contrast media.
OBJECTIVE
The purpose of this study was to examine the potential of intravascular gadolinium (Gd)-chelates in discriminating acute from chronic myocardial infarctions (MIs).


BACKGROUND
A potential limitation of delayed contrast enhanced magnetic resonance imaging with standard extracellular Gd-chelates is its inability to distinguish acute from chronic MIs.


METHODS
Eight pigs with MIs were studied at 3 days and 8 weeks. Inversion recovery gradient echo (IR-GRE), T(1)-turbo spin echo (TSE), and T(2)-TSE images were acquired before and after administration of intravascular and extracellular Gd-chelates. Triphenyltetrazolium chloride (TTC) was used to delineate infarctions at postmortem. Masson's trichrome and Biotinylated Bandeiria simplicifolia Isolectin B4 stains were used to characterize scarred myocardium. Analysis of variance was used to compare signal intensity (SI) ratios and determine differences in infarct extent.


RESULTS
The intravascular agent produced differential enhancement of acute infarctions at 3 days (SI ratio 5.8 +/- 1.3) but not at 8 weeks (1.6 +/- 0.4, p < 0.01). The extracellular agent provided differential enhancement of both acute (SI ratio 7.7 +/- 1.4) and chronic (7.5 +/- 0.9) infarctions. The extents of enhanced regions in acute infarctions were not different after intravascular (16.0 +/- 1.3%) or extracellular (17.1 +/- 1.7%) agents; at 8 weeks the extent of extracellular enhanced and TTC regions were smaller (13.2 +/- 1.4% and 12.0 +/- 1.5%, respectively). Masson's trichrome stain demonstrated dense scar tissue, signaling the complete healing of infarction. The vascular stain showed that scar tissue contained fewer microvessels oriented in a haphazard array.


CONCLUSIONS
The combination of intravascular and extracellular Gd-chelates discriminates acute from chronic infarctions on delayed images. This double contrast agent approach can be used to determine the age and extent of infarctions.
Saeed
Maythem
M
Department of Radiology, University of California San Francisco, San Francisco, California 94134-0628, USA. Maythem.Saeed@radiology.UCSF.edu
Weber
Oliver
O
Lee
Randall
R
Do
Loi
L
Martin
Alastair
A
Saloner
David
D
Ursell
Philip
P
Robert
Philippe
P
Corot
Claire
C
Higgins
Charles B
CB
D000818:Animals; D001794:Blood Pressure; D001808:Blood Vessels; D002614:Chelating Agents / Q000008:administration & dosage; D002908:Chronic Disease; D002921:Cicatrix / Q000209:etiology*; D003287:Contrast Media / Q000008:administration & dosage; D003937:Diagnosis, Differential; D045604:Extracellular Fluid; D005682:Gadolinium; D006339:Heart Rate; D006571:Heterocyclic Compounds / Q000008:administration & dosage; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging; D009203:Myocardial Infarction / Q000150:complications* / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D009206:Myocardium / Q000473:pathology; D009942:Organometallic Compounds / Q000008:administration & dosage; D013997:Time Factors
D002614:Chelating Agents; D003287:Contrast Media; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; D005682:Gadolinium; C435266:contrast agent P792