BACKGROUND Left atrial (LA) remodeling after an acute myocardial infarction (MI) is poorly characterized regarding its determinants or its effect on ischemic mitral regurgitation (MR) development. OBJECTIVES The purpose of this study was: 1) to compare LA structural remodeling in experimental MI swine models recapitulating the effects of left ventricular (LV) dysfunction, ischemic MR, and left atrial infarction (LAI); and 2) to analyze how LA remodeling influences ischemic MR development. METHODS Three models of MI were generated: 1) proximal left circumflex (LCx) coronary artery occlusion involving the LA branch (LAI group); 2) proximal LCx occlusion not involving the LA branch (LCx group); and 3) left anterior descending (LAD) occlusion (LAD group). Serial cardiac magnetic resonance scans were performed to define LA and LV remodeling and ischemic MR, and were correlated with histology. RESULTS Occlusion of the LA branch (LAI group) induced a greater degree of LA dilation at 1 and 8 weeks post-MI than the LCx and LAD groups, along with early and severe impairment of LA function. In the LCx and LAD groups, LA dysfunction was less pronounced and not consistent. Development of ischemic MR was more pronounced in the LAI group than in the LCx group. Histology confirmed atrial infarction with extensive fibrosis in the LAI group and interstitial fibrosis in the LCx group. In the LAD group, LA remodeling was not observed by cardiac magnetic resonance or histology. CONCLUSIONS We provide the first experimental evidence of the deleterious effect of acute LAI on atrial structural remodeling, characterized by early LA dilation, dysfunction, and fibrosis, and early occurrence of ischemic MR.

中文翻译：

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心房梗塞和缺血性二尖瓣关闭不全有助于 MI 后左心房重塑

背景 急性心肌梗死 (MI) 后的左心房 (LA) 重构在其决定因素或其对缺血性二尖瓣关闭不全 (MR) 发展的影响方面的特征很差。目的 本研究的目的是： 1) 比较实验 MI 猪模型中 LA 结构重构，重现左心室 (LV) 功能障碍、缺血性 MR 和左心房梗塞 (LAI) 的影响；2) 分析 LA 重塑如何影响缺血性 MR 的发展。方法 产生三种 MI 模型：1) 近端左回旋支 (LCx) 冠状动脉闭塞累及 LA 分支（LAI 组）；2) 不累及 LA 分支的近端 LCx 闭塞（LCx 组）；3）左前降支（LAD）闭塞（LAD组）。进行连续心脏磁共振扫描以确定 LA 和 LV 重塑和缺血性 MR，并与组织学相关。结果 与 LCx 和 LAD 组相比，LA 分支的闭塞（LAI 组）在 MI 后 1 周和 8 周诱导了更大程度的 LA 扩张，以及 LA 功能的早期和严重损害。在 LCx 和 LAD 组中，LA 功能障碍不太明显且不一致。LAI 组缺血性 MR 的发展比 LCx 组更明显。组织学证实 LAI 组为广泛纤维化的心房梗塞，LCx 组为间质纤维化。在 LAD 组中，心脏磁共振或组织学未观察到 LA 重塑。结论 我们提供了急性 LAI 对心房结构重塑有害影响的第一个实验证据，