Quantifying the area at risk using the infarct lateral border: importance of infarct transmurality
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Quantifying the area at risk using the infarct lateral border: importance of infarct transmurality Christoph J Jensen*, Lowie M Van Assche, Han W Kim, Lubna Bhatti, Peter Filev, Ki-Young Kim, Michele Parker, Igor Klem, Raymond J Kim From 15th Annual SCMR Scientific Sessions Orlando, FL, USA. 2-5 February 2012 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 delayedenhancement-CMR (DE-CMR) has been compared with surrogates of the AAR (ECG, angiographic scores, T2weighted-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 Duke Cardiovascular MR Center, Duke University Medical Center, Durham, NC, USA
(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), InfarctLatBor PATH 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% (Figure 1). Similarly, on a perheart 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
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