Table_2_Microvascular and Prognostic Effect in Lesions With Different Stent Expansion During Primary PCI for STEMI: Insights From Coronary Physiology and Intravascular Ultrasound.docx

BackgroundWhile coronary stent implantation in ST-elevation myocardial infarction (STEMI) can mechanically revascularize culprit epicardial vessels, it might also cause distal embolization. The relationship between geometrical and functional results of stent expansion during the primary percutaneous coronary intervention (pPCI) is unclear.
ObjectiveWe sought to determine the optimal stent expansion strategy in pPCI using novel angiography-based approaches including angiography-derived quantitative flow ratio (QFR)/microcirculatory resistance (MR) and intravascular ultrasound (IVUS).
MethodsPost-hoc analysis was performed in patients with acute STEMI and high thrombus burden from our prior multicenter, prospective cohort study (ChiCTR1800019923). Patients aged 18 years or older with STEMI were eligible. IVUS imaging, QFR, and MR were performed during pPCI, while stent expansion was quantified on IVUS images. The patients were divided into three subgroups depending on the degree of stent expansion as follows: overexpansion (>100%), optimal expansion (80%−100%), and underexpansion (<80%). The patients were followed up for 12 months after PCI. The primary endpoint included sudden cardiac death, myocardial infarction, stroke, unexpected hospitalization or unplanned revascularization, and all-cause death.
ResultsA total of 87 patients were enrolled. The average stent expansion degree was 82% (in all patients), 117% (in overexpansion group), 88% (in optimal expansion), and 75% (in under-expansion). QFR, MR, and flow speed increased in all groups after stenting. The overall stent expansion did not affect the final QFR (p = 0.08) or MR (p = 0.09), but it reduced the final flow speed (−0.14 cm/s per 1%, p = 0.02). Under- and overexpansion did not affect final QFR (p = 0.17), MR (p = 0.16), and flow speed (p = 0.10). Multivariable Cox analysis showed that stent expansion was not the risk factor for MACE (hazard ratio, HR = 0.97, p = 0.13); however, stent expansion reduced the risk of MACE (HR = 0.95, p = 0.03) after excluding overexpansion patients. Overexpansion was an independent risk factor for no-reflow (HR = 1.27, p = 0.02) and MACE (HR = 1.45, p = 0.007). Subgroup analysis shows that mild underexpansion of 70%−80% was not a risk factor for MACE (HR = 1.11, p = 0.08) and no-reflow (HR = 1.4, p = 0.08); however, stent expansion <70% increased the risk of MACE (HR = 1.36, p = 0.04).
ConclusionsStent expansion does not affect final QFR and MR, but it reduces flow speed in STEMI. Appropriate stent underexpansion of 70–80% does not seem to be associated with short-term prognosis, so it may be tolerable as noninferior compared with optimal expansion. Meanwhile, overexpansion and underexpansion of <70% should be avoided due to the independent risk of MACEs and no-reflow events.

背景：尽管ST段抬高型心肌梗死（ST-elevation myocardial infarction, STEMI）患者接受冠状动脉支架植入术可通过机械方式实现罪犯心外膜血管的血运重建，但该操作也可能引发远端栓塞。当前针对直接经皮冠状动脉介入治疗（primary percutaneous coronary intervention, pPCI）过程中支架扩张的几何与功能结局之间的关联尚不明确。
研究目的：本研究旨在依托基于血管造影的新型评估方法——包括血管造影衍生定量血流分数（angiography-derived quantitative flow ratio, QFR）、微循环阻力（microcirculatory resistance, MR）以及血管内超声（intravascular ultrasound, IVUS），明确pPCI术中的最优支架扩张策略。
研究方法：本研究为回顾性分析，数据来源于本团队既往一项多中心前瞻性队列研究（ChiCTR1800019923），纳入对象为合并高血栓负荷的急性STEMI患者。纳入标准为年龄≥18岁的STEMI患者。术中于pPCI过程中完成IVUS成像、QFR及MR检测，并通过IVUS图像量化支架扩张程度。根据支架扩张程度将患者分为3个亚组：过度扩张组（>100%）、最优扩张组（80%~100%）以及扩张不足组（<80%）。所有患者于PCI术后接受为期12个月的随访。主要终点包括心源性猝死、心肌梗死、脑卒中、非预期住院或计划性外血运重建以及全因死亡。
研究结果：本研究共纳入87例患者。所有患者的平均支架扩张程度为82%，其中过度扩张组为117%、最优扩张组为88%、扩张不足组为75%。支架植入后，所有亚组的QFR、MR及血流速度均有所升高。总体支架扩张程度对最终QFR（p=0.08）及MR（p=0.09）无显著影响，但可降低最终血流速度（每增加1%，血流速度降低0.14cm/s，p=0.02）。单纯扩张不足或过度扩张均未对最终QFR（p=0.17）、MR（p=0.16）及血流速度（p=0.10）产生显著影响。多变量Cox回归分析显示，总体支架扩张程度并非主要不良心血管事件（Major Adverse Cardiovascular Events, MACE）的独立危险因素（风险比HR=0.97，p=0.13）；但在剔除过度扩张组患者后，支架扩张程度可降低MACE发生风险（HR=0.95，p=0.03）。过度扩张是无复流现象（HR=1.27，p=0.02）及MACE（HR=1.45，p=0.007）的独立危险因素。亚组分析显示，70%~80%的轻度扩张不足并非MACE（HR=1.11，p=0.08）及无复流现象（HR=1.4，p=0.08）的危险因素；但支架扩张程度<70%则会升高MACE发生风险（HR=1.36，p=0.04）。
研究结论：STEMI患者的支架扩张程度对最终QFR及MR无显著影响，但可降低血流速度。70%~80%的适度扩张不足似乎与短期预后无显著关联，因此相较于最优扩张，该程度的扩张不足可被认为是非劣效的，具有临床可接受性。与此同时，由于过度扩张及<70%的扩张不足均存在MACE及无复流事件的独立风险，应避免此类情况发生。