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- Open Access
Quantitative evaluation of scar, area at risk, and wall thickening in a porcine model of sub-acute myocardial infarction (MI)
© Krishnamurthy et al; licensee BioMed Central Ltd. 2013
- Published: 30 January 2013
- Normalize Wall Thickness
- Scar Burden
- Scar Region
- Short Axis Orientation
- Cine SSFP
Elevated signal intensity (SI) in T2w images is often designated as area-at-risk (AAR) following acute/sub-acute MI. While AAR has been qualitatively associated with reductions in wall thickening (WT), quantitative information between the two is not available [1–3]. Quantitative SI threshold for classifying regions as AAR, and its effect on regional WT have also been not reported.
Effect of SI threshold on estimating AAR,
Reduction in WT with AAR at increasing SI thresholds, and
Correlation between AAR and percent scar.
Cine SSFP: TR/TE/α = 3/1.5 ms/45°; acquired temporal resolution: 12 ms.
Delayed enhancement MRI (DE-MRI): 10 min after 0.2 mmol/kg of contrast, scar was visualized using a gated IR-TFE sequence with inversion delay (TI) adjusted to null normal myocardium.
Dual-IR T2W imaging (BB): Effective TE/TR: 80 ms/2*RR interval; TSE readout.
Normalized wall thickness (nWT) per segment = (WTES - WTED)/( WTED), where ED = End-Diastole, ES-End-Systole.
Segmental scar burden, defined as ratio of pixels designated as scar to total number of pixels in each segment of DE-MRI. Scar pixel is one with SI > [mean + 5*Standard Deviation (SD) of normal remote myocardium].
Segmental AAR, defined as regions in BB images with SI > mean + n*SD of normal remote myocardium (AAR with n = 2, 3, 4 are AAR_2SD, AAR_3SD, and AAR_4SD, respectively).
As a share of total myocardium, AAR burden was significantly higher (43 to 57 %) than scar burden (30 %) (Table 1). Although total AAR burden progressively declined with increasing T2w SI cut-offs, it was not lower than scar burden at any threshold evaluated (AAR_4SD > Scar burden).
AAR and scar burden calculated for LV, expressed as a percentage of total myocardial mass. AAR Burden at different quantifying metric is consistently greater than scar burden (p<0.01).
57 ± 6.4%
49.8 ± 6.8%
43.6 ± 8%
30.2 ± 14.7%
Spatially, AAR overlapped, and extended beyond scar regions.
Reduction in segmental nWTwas lower in AAR regions that did not overlap scar region compared to those segments that did(108 ± 36 % vs 91 ± 29 %, Figure 2).
In sub-acute AMI, AAR is significantly larger than scar. In non-overlapping regions of AAR and scar, nWT, while diminished compared to normal remote myocardium, is significantly better than in regions of scar.
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