MR新技术在冠状动脉微栓塞早期检测及其延迟强化演变机制的研究

Coronary microembolization (CME) is a frequent complication following acute coronary syndromes and percutaneous coronary interventions. Accurate detection of CME is important, because previous studies have shown that CME is independently associated with adverse ventricular remodeling and patient prognosis. It's difficult to detect CME through X-ray coronary angiography - the reference standard for the diagnosis of coronary artery disease and CME becomes a focus of research. Our previous study has shown that hyperenhancement was detectable at 6 hours after coronary microembolization in animal experiments using late gadolinium-enhanced cardiovascular MRI and the hyperenhanced areas were largely decreased or even disappeared and the left ventricular volume was enlarged indicating ventricular remodeling at 1 week. Based on previous study, we believe that further study need to be performed on the following issues: the early characterization of coronary microembolization and the mechanism of delayed enhancement phenomenon of CME. The latter may be attributed to the microinfarction and inflammatory response to CME. However, the sequence of late gadolinium-enhanced MRI belongs to gradient echo T1-weighted imaging and is difficult to show the myocardial edema secondary to microinfarction and inflammation due to CME directly. In this study, we plan to induce swine model by the injection of microspheres into the left coronary artery and concentrate on the visualization of myocardial edema due to CME using turbo spin-echo T2-weighted BLADE sequence in order to detect the early characterization of CME and provide useful information for analyzing the mechanism of delayed enhancement phenomenon of CME. The study will also perform the intervention studies with glucocorticoid/nicorandil treatment and evaluate the heart function, TNF~α, and cTnT to interpret the mechanism of delayed enhancement phenomenon of CME. Furthermore, the study will also perform the comparison of the effects of methylprednisolone versus nicorandil on CME using multimodality MR imaging techniques. We also hope that a new approach could be developed for the detection of the early characrization of CME and the evaluation of drug efficacy through this study.

冠脉微栓塞是急性冠脉综合征和冠心病介入术中常见而重要的临床事件，危害较大，但诊断冠心病的"金标准"冠脉造影术无法显示微小动脉病变，因此，冠脉微栓塞成为当前研究的热点。我们前期MR研究发现：微栓塞后6小时受累心肌可出现延迟强化，1周后其范围显著缩小甚至消失，伴随左室重构，其延迟强化及其消失的演变过程是何机理？目前尚未完全明了，仅用微梗死灶难以解释急性期较大范围延迟强化，我们推测炎症反应也起重要作用，然而延迟增强扫描（梯度回波T1WI）难以显示微栓塞所致心肌水肿。因此，本研究拟建立微栓塞动物（猪）模型，利用MR-BLADE刀锋序列能清楚显示心肌水肿的特点，结合MR心功能评价、血液及心肌相关标志物的检测，并进行抗炎及改善微循环的干预研究，为探讨微栓塞MR延迟强化的病理生理意义及机制提供科学依据，并有望为更早期显示微栓塞病变和评价药物的疗效开辟新的途径以及提供基础的研究资料。

冠脉微栓塞常见于急性冠脉综合征和冠心病介入术中，危害较大，但冠脉造影术难以显示微小动脉病变，需深入研究，本研究建立了冠脉微栓塞家猪模型，应用MRI心脏扫描技术评价冠脉微栓塞急性期的特征，探讨微栓塞病变延迟强化演变的病理生理机制。本研究发现，BLADE刀锋技术与传统的Cartesian方式相比，可提高图像SNR、减轻运动伪影；冠脉微栓塞急性期MRI出现心肌延迟强化伴收缩功能障碍，亚急性期延迟强化消退、收缩功能部分恢复，BLADE刀锋序列于部分实验动物显示心肌水肿；微栓塞引起的梗死灶可不为肉眼所见，HE染色显微镜下可发现微梗死灶，伴炎症细胞浸润，微栓塞后的血清TNF-α水平较基础状态增加（P < 0.05）；糖皮质激素干预研究发现，微栓塞急性期心肌延迟强化得到显著抑制，LVEF高于对照组（P < 0.05），亚急性期左室重构现象也较对照组得到改善。研究结果表明，MRI对于评价冠脉微栓塞病变，具有较高的价值，微栓塞导致的炎症反应在心肌延迟强化的演变过程中起着重要作用，但研究也发现，微栓塞引起的心肌血流灌注改变及心肌损伤机制较为复杂，还需进一步研究。