Abstract 12435: Detection of Injured Border Zone Myocardium Using Manganese-Enhanced and Delayed-Enhanced MRI in a Pig Ischemia-Reperfusion Model
Background: Accurate myocardial tissue characterization could enhance ischemic heart disease treatment. Delayed gadolinium (Gd) enhancement MRI (DEMRI) can overestimate infarct size and cannot reliably discern injured from scarred myocardium. Manganese (Mn)-enhanced MRI (MEMRI) produces a T1-shortening effect by intracellular accumulation of Mn via Ca2+-channels in viable cardiomyocytes.
Hypothesis: We tested combined 3D DEMRI / MEMRI in a pig ischemia-reperfusion (IR) model to identify injured, but salvageable, myocardium.
Methods: 22 adult pigs underwent 60min LAD IR. 21d post-IR, 3T cardiac MRI was performed (Signa 3T HDx, GE, USA). Images were analyzed by GE Advantage Workstation with manual LV mass/scar volume tracing. MEMRI was obtained 25–40min after a 0.7cc/kg i.v. bolus of MnCl2 (Eaglevision Inc. Harrisburgh, PA). 3D DEMRI was acquired 10–20min post-Gd injection (0.2 mmol/kg Magnevist, Bayer, Germany). Infarct volumes were traced manually after TTC fibrosis stain of explanted hearts. Tissue electron microscopy (TEM, JEOL Inc., Tokyo, Japan) from infarct, border zone (BZ), and remote myocardium was performed, scoring 16 criteria from 10 nuclei/region (1-worst, 5-best) for ultrastructural integrity. *−P<0.05 by Anova.
Results: Average EF (%) was low (25±5, n=22). DEMRI scar volume correlated highly (r2=0.91, p<0.05) with TTC scar volume. MEMRI scar (signal defect) volume% was significantly lower (6.6±2.5%*, n=13) vs. DEMRI (20.4±1.7, n=13). Digital subtraction revealed overlapping MEMRI(+) and DEMRI(+) areas (Figure), and these BZ regions displayed lower SNR than did core infarct or remote zone, for DEMRI and MEMRI, respectively. Cell integrity and contractile elements by TEM were significantly preserved in BZ (4.4±0.4*) vs. infarct areas (1.3±0.3), despite transmural DEMRI.
Conclusions: Subtraction of MEMRI defect from DEMRI signal may detect viable, injured myocardium in BZ regions that appear nonviable by DEMRI alone.
- Cardiac MRI
- Ischemia reperfusion
- Ischemic heart disease
- Cardiovascular imaging
- Myocardial revascularization
- © 2010 by American Heart Association, Inc.