Cardiovascular Research Institute, Icahn School of Medicine at Mount Sinai, New York, New York.
Am J Physiol Heart Circ Physiol. 2022 Jun 1;322(6):H914-H923. doi: 10.1152/ajpheart.00009.2022. Epub 2022 Mar 25.
Left atrial (LA) dysfunction is one of the predictive factors of worse outcomes after mitral valve surgery for mitral regurgitation (MR). We aimed to investigate the effect of MR etiology on progression of LA remodeling in swine MR models. MR was induced in 14 Yorkshire pigs using catheter-based procedures. Seven pigs underwent simultaneous occlusions of the left circumflex artery and the diagonal branch, which resulted in ischemic mitral regurgitation (IMR group). The other seven pigs underwent chordal severing to induce leaflet prolapse simulating degenerative mitral regurgitation (DMR group). Changes in LA volume and function were assessed at baseline, 1 mo, and 3 mo using echocardiography and hemodynamic evaluations. Histopathological assessments were conducted to evaluate LA hypertrophy and fibrosis. At 3 mo, quantitative MR severity was comparable and severe in both groups. Despite the similar degree of MR, minimum LA volume index increased significantly more in the IMR group (IMR: 11.9 ± 6.4 to 73.2 ± 6.4 mL/m, DMR: 10.7 ± 6.4 to 29.5 ± 6.4 mL/m, = 0.004). Meanwhile, increase in maximum LA volume index was similar between the groups, resulting in lower LA emptying function in the IMR group (IMR: 60.1 ± 3.1 to 29.4 ± 3.1%; DMR: 62.4 ± 3.1 to 58.2 ± 3.1%, = 0.0003). LA reservoir strain assessed by echocardiography was also significantly lower in the IMR group. Histological analyses revealed increased LA cellular hypertrophy and fibrosis in the IMR group. In conclusion, ischemic MR is associated with aggressive remodeling and reduced emptying function compared with the MR due to leaflet prolapse. Earlier intervention might be necessary for ischemic MR to prevent LA remodeling. We show different LA structural and functional remodeling patterns between ischemic MR and MR due to leaflet prolapse. Severe ischemic MR was accompanied by extensive LA remodeling, which may be associated with poor clinical outcomes. Our data suggest that detailed structural and functional LA remodeling assessment is important for managing IMR and to determine the presence of LA ischemia.
左心房（LA）功能障碍是二尖瓣反流（MR）手术后预后较差的预测因素之一。我们旨在研究 MR 病因对猪 MR 模型中 LA 重构进展的影响。通过基于导管的程序在 14 头约克夏猪中诱导 MR。7 头猪同时闭塞左回旋支和对角支，导致缺血性二尖瓣反流（IMR 组）。另外 7 头猪行腱索切断术导致瓣叶脱垂模拟退行性二尖瓣反流（DMR 组）。通过超声心动图和血流动力学评估，在基线、1 个月和 3 个月时评估 LA 容积和功能的变化。进行组织病理学评估以评估 LA 肥大和纤维化。在 3 个月时，两组的定量 MR 严重程度相当且严重。尽管 MR 程度相似，但 IMR 组的最小 LA 容积指数增加明显更多（IMR：11.9±6.4 至 73.2±6.4 mL/m，DMR：10.7±6.4 至 29.5±6.4 mL/m，=0.004）。同时，两组之间最大 LA 容积指数的增加相似，导致 IMR 组的 LA 排空功能降低（IMR：60.1±3.1 至 29.4±3.1%；DMR：62.4±3.1 至 58.2±3.1%，=0.0003）。通过超声心动图评估的 LA 储器应变在 IMR 组也明显降低。组织学分析显示 IMR 组 LA 细胞肥大和纤维化增加。总之，与瓣叶脱垂引起的 MR 相比，缺血性 MR 与侵袭性重构和排空功能降低相关。为了防止 LA 重构，可能需要对缺血性 MR 进行更早的干预。我们显示了缺血性 MR 和瓣叶脱垂引起的 MR 之间不同的 LA 结构和功能重塑模式。严重的缺血性 MR 伴有广泛的 LA 重构，这可能与不良的临床结果相关。我们的数据表明，详细的 LA 结构性和功能性重构评估对于管理 IMR 和确定 LA 缺血的存在很重要。
