测量血管直径、优化支架植入
图5—0—26 正向、逆向导丝位置和关系示意图
正向、逆向都位于斑块内时可前向球囊扩张和逆向导丝前送；当正向位于斑块内、逆向位于内膜下时可前向球囊扩张或更远端交汇；当正向位于内膜下、逆向位于斑块内时可逆向导丝前送和更近端处交汇
CTO远段血管在开通之前长期处于低灌注状态，冠状动脉造影可能显示为弥漫性病变且管腔较小，根据冠状动脉造影定位支架较为困难。Okuya等人的研究表明，开通后的CTO远段血管在晚期随访时会明显增大，特别是无中、重度钙化斑块的血管。另在CTO PCI操作后出现较大夹层和血肿时，无法进行正向造影来指导支架的选择和植入，IVUS可以测量血管的直径和长度来指导支架尺寸和植入位置的选择。IVUS还可以发现造影难以发现的闭塞前降支远端的心肌桥，尽量避免在心肌桥段植入支架。与冠状动脉造影相比，植入支架后IVUS可以更准确地评价支架的贴壁和膨胀情况，发现支架边缘的夹层、血肿、残余狭窄等，减少支架内血栓和支架内再狭窄的发生率。Kim等人的研究表明，IVUS指导的CTO介入治疗虽然没有明显地降低死亡率，但与常规造影指导的CTO介入治疗相比，明显地降低了药物洗脱支架植入后12个月内的严重心脏不良事件发生率。
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