Mitral Apparatus Assessment by Delayed Enhancement CMR : Relative Impact of Infarct Distribution on Mitral Regurgitation
JACC: Cardiovascular Imaging
Objectives: This study sought to assess patterns and functional consequences of mitral apparatus infarction after acute myocardial infarction (AMI). Background: The mitral apparatus contains 2 myocardial components: papillary muscles and the adjacent left ventricular (LV) wall. Delayed-enhancement cardiac magnetic resonance (DE-CMR) enables in vivo study of inter-relationships and potential contributions of LV wall and papillary muscle infarction (PMI) to mitral regurgitation (MR). Methods: Multimodality imaging was performed: CMR was used to assess mitral geometry and infarct pattern, including 3D DE-CMR for PMI. Echocardiography was used to measure MR. Imaging occurred 27 ± 8 days after AMI (CMR, echocardiography within 1 day). Results: A total of 153 patients with first AMI were studied; PMI was present in 30% (n = 46 [72% posteromedial, 39% anterolateral]). When stratified by angiographic culprit vessel, PMI occurred in 65% of patients with left circumflex, 48% with right coronary, and only 14% of patients with left anterior descending infarctions (p <0.001). Patients with PMI had more advanced remodeling as measured by LV size and mitral annular diameter (p <0.05). Increased extent of PMI was accompanied by a stepwise increase in mean infarct transmurality within regional LV segments underlying each papillary muscle (p <0.001). Prevalence of lateral wall infarction was 3-fold higher among patients with PMI compared to patients without PMI (65% vs. 22%, p <0.001). Infarct distribution also impacted MR, with greater MR among patients with lateral wall infarction (p = 0.002). Conversely, MR severity did not differ on the basis of presence (p = 0.19) or extent (p = 0.12) of PMI, or by angiographic culprit vessel. In multivariable analysis, lateral wall infarct size (odds ratio 1.20/% LV myocardium [95% confidence interval: 1.05 to 1.39], p = 0.01) was independently associated with substantial (moderate or greater) MR even after controlling for mitral annular (odds ratio 1.22/mm [1.04 to 1.43], p = 0.01), and LV end-diastolic diameter (odds ratio 1.11/mm [0.99 to 1.23], p = 0.056). Conclusions: Papillary muscle infarction is common after AMI, affecting nearly one-third of patients. Extent of PMI parallels adjacent LV wall injury, with lateral infarction—rather than PMI—associated with increased severity of post-AMI MR.
Chinitz, Jason S.; Chen, Debbie; Goyal, Parag; Wilson, Sean; Islam, Fahmida; Nguyen, Thanh; Wang, Yi; Hurtado Rua, Sandra M.; Simprini, Lauren; Cham, Matthew; Levine, Robert A.; Devereux, Richard B.; and Weinsaft, Jonathan W., "Mitral Apparatus Assessment by Delayed Enhancement CMR : Relative Impact of Infarct Distribution on Mitral Regurgitation" (2013). Mathematics Faculty Publications. 205.
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