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Quantifying the area at risk using the infarct lateral border: importance of infarct transmurality

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Journal of Cardiovascular Magnetic Resonance201214 (Suppl 1) :O24

https://doi.org/10.1186/1532-429X-14-S1-O24

  • Published:

Keywords

  • Myocardial Infarction
  • Left Atrium
  • Ischemia Time
  • Lateral Border
  • Precise Quantification

Background

The wavefront phenomenon describes the transmural progression of myocardial infarction (MI) from endocardium to epicardium with increasing ischemia duration. A corollary is once subendocardial MI has developed, the infarct lateral border (InfarctLatBor) delineates the Area-at-risk (AAR) lateral border, and thus, can be used to measure overall AAR size. However, with short ischemia time a confluent subendocardial layer of infarction may not develop, and InfarctLatBor may underestimate AAR size. The transmural extent of infarction necessary for InfarctLatBor to accurately reflect AAR size is unknown.

In-vivo assessment of InfarctLatBor with delayed-enhancement-CMR (DE-CMR) has been compared with surrogates of the AAR (ECG, angiographic scores, T2-weighted-CMR). However, no comparison exists with a pathology-based truth standard of the AAR (i.e microspheres). We sought to examine: (1) on pathology studies, the threshold of infarct transmurality necessary for the InfarctLatBor to accurately delineate the AAR, and (2) the ability of in-vivo DE-CMR (via InfarctlatBor assessment) to quantify the AAR in comparison with pathology.

Methods

In 15 canines, MI with various infarct transmuralities was produced by temporary occlusion (50-120mins) of the LAD or LCx. A complete LV short-axis stack (7mm thickness, no gap) of DE-CMR images were obtained following gadoversetamide administration (0.2mmol/kg). Prior to sacrifice, the infarct-related-artery was reoccluded at the same site (same suture) and microspheres (1-10μ, 2 million, Duke scientific corp.) were injected into the left atrium to determine AAR size (AARPATH). After TTC-staining the infarct lateral border was used to estimate AAR size (InfarctLabBorPATH).

Results

Comparing pathology-based measurements per-slice (N=114), InfarctLatBorPATH slightly underestimated AARPATH (28.2±25.9% vs. 28.9±25.4%, bias -0.6±2.9%, p=0.03), though correlation was excellent (r=0.994). In slices with mean infarct transmurality <10% InfarctlatBorPATH underestimated AARPATH, whereas no systematic under- or overestimation occurred when infarct transmurality was >10% (Figure1). Similarly, on a per-heart basis, in-vivo InfarctlatBorDE-CMR slightly underestimated AARPATH (25.2±13.3% vs. 26.8±12.4%, bias -1.6±2.5%, p=0.03), and again the correlation was excellent (r=0.979). The greatest underestimation (-8.4%ofLV) was found in the subject with lowest mean infarct transmurality (11%) and highest number of slices (N=4) with infarct transmurality <10%. Excluding this subject, the maximum bias was lower than -4%ofLV for all other subjects.
Figure 1
Figure 1

The infarct lateral border ((InfarctLatBor Path ) is used to estimate true area-at-risk size delineated by microspheres (AAR Path ). Note, underestimation of AAR size by the infarct lateral border occurs only in slices with mean infarct transmurality <10% (p<0.001). In groups with higher transmurality no bias was found (p=N.S.).

Conclusions

The lateral border of infarction allows for precise quantification of true AAR size unless a subendocardial layer of infarction less than 10% transmural is present. In-vivo DE-CMR assessment of the infarct lateral border can be used to accurately estimate AAR size, however, underestimation may occur if mean infarct transmurality is near 10%.

Funding

This study was funded in part by following NIH-grant: 5R01HL064726-07.

Authors’ Affiliations

(1)
Duke Cardiovascular MR Center, Duke University Medical Center, Durham, NC, USA

Copyright

© Jensen et al; licensee BioMed Central Ltd. 2012

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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