Purpose

This study was to evaluate the effects of ischemic mitral regurgitation (IMR) on vortex formation and leaflet dynamics using an established porcine infarct model of IMR.

Methods

Using direct coronary ligation, five animals were subjected to a posterolateral myocardial infarction (MI) followed by an MRI at 12-weeks post MI. MR imaging consisted of 4D time-resolved left ventricular (LV) flow, full coverage 2D LV cine, and high resolution 2D cine of mitral valve dynamics. Five additional naïve animals underwent identical imaging protocols to serve as controls. Image analysis was performed to obtain mitral transvalvular flows as well as LV volumes throughout the cardiac cycle. In addition, anterior to posterior mid-leaflet tip distances were measured throughout the cardiac cycle for determination of temporal leaflet dynamics.

Results

It was found IMR caused asymmetric vortex ring formation with the anterior vortex having a lower vorticity relative to its posterior counterpart. In contrast, normal ventricles create symmetric and tightly curled vortices in the basal chamber just underneath the mitral leaflets which conserve kinetic energy and aid in effective ejection. IMR animals were also evaluated for leaflet separation and were found to have a greater leaflet opening and achieved peak vorticity and peak leaflet opening later than control animals.

Conclusion

In conclusion, this study shows the effects that altered vortex formation, due to IMR, can have on ventricular filling and leaflet dynamics. These findings have important implications for understanding blood flow through the dilated heart and how ring annuloplasty and volume reduction interventions may influence mitral valve dynamics.

中文翻译：

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在缺血性二尖瓣反流模型中，心内血流模式的改变影响二尖瓣的动力学

目的

本研究旨在使用已建立的 IMR 猪梗塞模型评估缺血性二尖瓣反流 (IMR) 对涡流形成和瓣叶动力学的影响。

方法

使用直接冠状结扎，五只动物在心肌梗死后 12 周接受了后外侧心肌梗死 (MI)，然后进行了 MRI。MR 成像包括 4D 时间分辨左心室 (LV) 血流、全覆盖 2D LV 电影和高分辨率 2D 二尖瓣动态电影。另外五只幼稚动物接受了相同的成像方案作为对照。进行图像分析以获得整个心动周期的二尖瓣跨瓣流量以及 LV 体积。此外，在整个心动周期中测量前到后中叶尖端距离，以确定颞叶动力学。

结果

发现 IMR 导致不对称涡环形成，前涡流相对于其后涡流具有较低的涡量。相比之下，正常心室在二尖瓣正下方的基底腔中产生对称且紧密卷曲的涡流，从而节省动能并有助于有效射血。还评估了 IMR 动物的小叶分离，发现其具有更大的小叶开口，并且比对照动物晚达到峰值涡度和峰值小叶开口。

结论

总之，这项研究表明，由于 IMR，涡流形成的改变可能对心室充盈和瓣叶动力学产生影响。这些发现对于了解通过扩张心脏的血流以及环成形术和减容干预如何影响二尖瓣动力学具有重要意义。