Spence J David
Stroke Prevention and Atherosclerosis Research Centre, Robarts Research Institute, Western University, 1400 Western Road, London, Ontario, Canada N6G 2V4.
Semin Vasc Surg. 2017 Mar;30(1):62-66. doi: 10.1053/j.semvascsurg.2017.04.011. Epub 2017 Apr 27.
In the United States, 90% of carotid intervention is being performed for asymptomatic carotid stenosis, even though 90% of patients would be better treated with intensive medical therapy. This is being justified by comparing risks of stroke or death with medical therapy during clinical trials completed decades ago (approximately 2% per year) with risks of intervention with carotid artery stenting (CAS) versus carotid endarterectomy in recent trials that did not have a medical arm. Such extrapolations are, simply put, invalid. Even though the two most recent papers comparing carotid endarterectomy with CAS reported that the long-term risk (after first deducting periprocedural risks) is similar to that with medical therapy (approximately 0.5% per year), when the periprocedural risks are considered (approximately 3% with stenting v 1.5% with CAS), most patients would be better treated with intensive medical therapy. Furthermore, it must be recognized that the low risks observed in clinical trials with highly selected surgeons and interventionalists are much lower than in real-world practice. It is therefore necessary to have ways to identify, among patients with asymptomatic carotid stenosis, the few (approximately 10% to 15%) who could benefit from intervention. Indicators of vulnerable plaque, such as ulceration, juxtaluminal lucent plaque, intraplaque hemorrhage on magnetic resonance imaging, and plaque inflammation on positron emission tomography/computed tomography are in development for that purpose. The best-validated approach is detection of microemboli on transcranial Doppler. A prospective single-center study of 468 patients showed that microemboli identified high-risk asymptomatic stenosis; this was validated by a prospective multicenter international study in 467 patients. Increased risk with microemboli persisted in the era of lower risks with intensive medical therapy. Patients with asymptomatic carotid stenosis should not be offered CAS or carotid endarterectomy without first being identified as high risk; percent stenosis does not do so. Currently, the best way to improve the risk to benefit ratio for intervention is transcranial Doppler embolus detection.
在美国，90%的颈动脉干预是针对无症状性颈动脉狭窄进行的，尽管90%的患者采用强化药物治疗效果会更好。通过将几十年前完成的临床试验中药物治疗的中风或死亡风险（每年约2%）与近期未设药物治疗组的试验中颈动脉支架置入术（CAS）与颈动脉内膜切除术的干预风险进行比较，这种做法被认为是合理的。简单地说，这种推断是无效的。尽管最近两篇比较颈动脉内膜切除术与CAS的论文报告称，长期风险（在首先扣除围手术期风险后）与药物治疗相似（每年约0.5%），但考虑围手术期风险时（支架置入术约为3%，CAS为1.5%），大多数患者采用强化药物治疗效果会更好。此外，必须认识到，在由经过高度挑选的外科医生和介入专家进行的临床试验中观察到的低风险远低于实际临床实践中的风险。因此，有必要找到方法，在无症状性颈动脉狭窄患者中识别出少数（约10%至15%）可能从干预中获益的患者。为此，正在研发易损斑块的指标，如溃疡、管腔旁透亮斑块、磁共振成像上的斑块内出血以及正电子发射断层扫描/计算机断层扫描上的斑块炎症。经过最佳验证的方法是经颅多普勒检测微栓子。一项对468例患者的前瞻性单中心研究表明，微栓子可识别出高风险无症状狭窄；这在一项对467例患者的前瞻性多中心国际研究中得到了验证。在强化药物治疗风险降低的时代，微栓子导致的风险增加依然存在。无症状性颈动脉狭窄患者在未首先被确定为高风险之前，不应接受CAS或颈动脉内膜切除术；狭窄百分比并不能做到这一点。目前，改善干预风险效益比的最佳方法是经颅多普勒栓子检测。
