光学相关断层摄影技术观察壁冠状动脉的可行性研究

Morphology of myocardial bridging shown on optical coherence tomography

目的 讨论光学相关断层摄影技术观察壁冠状动脉的可行性。方法 选择36名心肌桥（myocardial bridging,MB）患者（即冠脉造影可见“挤奶现象”的患者）行光学相干断层摄影检查（optical coherence tomography,OCT）及血管内超声检查（intravascular ultrasound,IVUS）,并进一步用猪的心脏作为动物模型以确认与OCT图像相对应的组织学结构。结果 所有患者OCT检测均发现MB节段内一紧邻动脉管壁外的边界清晰、不均质的、低信号梭形区域;且在舒张期更易观察到这一特征性的图像表现。该梭形区域的最大弧度为176.3°±53.1°（106°~287.5°）,最大厚度为（0.41±0.12）mm（0.25~0.69 mm）。所有患者均在且只在肌桥节段外近段血管内检出动脉粥样硬化改变,仅1例患者在肌桥节段内发现了管壁内膜增厚。OCT所发现的梭形区域不同于IVUS图像中代表MB肌束的半月形无回声区域。另外,线性相关分析发现梭形区域弧度与管腔受压迫程度呈负相关（r=-0.403,P=0.004）。进一步的动物模型的组织学检查结果发现这一梭形、低信号区域是位于肌肉与动脉血管之间的结缔组织。结论 在造影和IVUS确诊的MB患者中,OCT检查可在肌桥节段发现一紧邻动脉管壁外的边界清晰、不均质的、低信号梭形区域,进一步组织学检查结果发现这一区域为动脉周围结缔组织,而非IVUS中代表肌束的半月形无回声区域。

Objective To assess the feasibility of optical coherence tomography （OCT） in diagnosis of myocardial bridging （ MB ）. Methods OCT and intravascular ultrasound （IVUS） were performed in 36 patients whose angiograms showed typical ＂milking effects＂ indicating MB. A porcine model was used to confirm the correlation of OCT image with histopathologic features of the disease. Results In all patients OCT showed specific fusiform, heterogeneous signal-poor tissue with a sharply delineated border surrounding the tunneled artery in the MB segment; which was more clear during diastole than systole and was not detected in non-MB segments. The maximal surrounding arc and thickness of this area measured 176.3°±53.1° （range from 106° to 287.5°） and （0. 41 ± 0. 12） mm（range from 0.25 mm to 0.69 mm）, respectively. Atherosclerosis occurred proximal to the MB segment in all patients, but intimal thickening in MB segment was observed only in one case. This OCT-detected fusiform area was distinct from the IVUS-detected echolucent crescent representing the myocardium surrounding the artery. Furthermore, a negative correlation between the fusiform arc and the compression ratio was found（ r = -0.403, P =0. 004）. In addition, histological examination in porcine heart model confirmed that the fusiform, heterogeneous signal-poor area was mainly composed of connective tissue and was located at the junction of MB myocardium and epicardium. Conclusion In patients with angiographically and IVUS documented MB, the OCT-detected sharp border, heterogeneous, signal-poor fusiform area is indicative of arterial tunneling through myocardium that is distinct from the echolucent muscle band found in IVUS and that represents peri-arterial connective tissue.