Rockman C B, Riles T S, Lamparello P J, Giangola G, Adelman M A, Stone D, Guareschi C, Goldstein J, Landis R
Department of Surgery, New York University Medical Center, N.Y. 10016, USA.
J Vasc Surg. 1997 Mar;25(3):423-31. doi: 10.1016/s0741-5214(97)70250-7.
Although it has been widely accepted as the evidence supporting prophylactic carotid endarterectomy, aspects of the Asymptomatic Carotid Atherosclerosis Study have left unease among clinicians who must decide which individuals without symptoms should undergo surgery. Additional confusion has been created by the fact that the several large randomized trials investigating the efficacy of carotid endarterectomy have classified and analyzed different categories of carotid stenosis. In an effort to provide more information on the natural history of asymptomatic, moderate carotid artery stenosis (50% to 79%), we have reviewed data on approximately 500 arteries.
Records of our vascular laboratory from 1990 to 1992 were reviewed. We identified 425 patients with asymptomatic, moderate carotid artery stenosis; 71 patients had bilateral stenoses in this category, resulting in 496 arteries for study.
The mean length of follow-up was 38 +/- 18 months. New ipsilateral strokes occurred in 16 (3.8%) patients. New ipsilateral transient ischemic attacks occurred in 25 (5.9%) patients. Documented progression of stenosis occurred in 48 (17%) of the 282 arteries for which a repeat duplex examination was available. Arteries that progressed to > 80% stenosis were significantly more likely to have caused strokes than those that remained in the 50% to 79% range (10.4% vs 2.1%, p < 0.02). Conversely, arteries that remained stable in the degree of stenosis were significantly more likely to have remained asymptomatic than those that progressed (92.7% vs 62.5%, p < 0.001). With life-table analysis the estimated cumulative ipsilateral stroke rate was 0.85% at 1 year, 3.6% at 3 years, and 5.4% at 5 years. The respective estimated cumulative transient ischemic attack rates were 1.9%, 5.5%, and 6.3%. The respective estimated cumulative rates for progression of stenosis were 4.9%, 16.7%, and 26.5%. Life-table comparison of ipsilateral stroke revealed a significantly higher cumulative rate among arteries that progressed in the degree of stenosis than among those that remained stable (p < 0.001).
Based on the low rate of permanent neurologic events in these cases, prophylactic carotid endarterectomy for the asymptomatic, moderately stenotic internal carotid artery cannot currently be recommended. The only factor that appears to predict increased risk for future stroke is progression of stenosis. Careful follow-up with serial repeat duplex examinations must be performed in these patients. Until there are widely accepted duplex parameters that can provide all clinicians with accurate identification of arteries with narrowing corresponding to 60% stenosis as defined by the Asymptomatic Carotid Atherosclerosis Study, all surgeons will need to be aware of specifically how their noninvasive laboratories are deriving their results. For the many laboratories that continue to use the University of Washington criteria, 80% should remain the level above which prophylactic carotid endarterectomy is warranted.
尽管无症状颈动脉粥样硬化研究（ACAS）已被广泛接受为支持预防性颈动脉内膜切除术的证据，但该研究的某些方面仍让必须决定哪些无症状个体应接受手术的临床医生感到不安。此外，由于几项调查颈动脉内膜切除术疗效的大型随机试验对不同类别的颈动脉狭窄进行了分类和分析，这又造成了更多困惑。为了提供更多关于无症状中度颈动脉狭窄（50%至79%）自然病史的信息，我们回顾了约500条动脉的数据。
回顾了我们血管实验室1990年至1992年的记录。我们确定了425例无症状中度颈动脉狭窄患者；其中71例患者双侧存在此类狭窄，从而有496条动脉可供研究。
平均随访时间为38±18个月。16例（3.8%）患者发生了新的同侧卒中。25例（5.9%）患者出现了新的同侧短暂性脑缺血发作。在有重复双功超声检查的282条动脉中，48条（17%）记录到狭窄进展。进展至狭窄>80%的动脉比狭窄程度保持在50%至79%范围的动脉更有可能导致卒中（10.4%对2.1%，p<0.02）。相反，狭窄程度保持稳定的动脉比进展的动脉更有可能一直无症状（92.7%对62.5%，p<0.001）。通过生命表分析，估计同侧卒中的累积发生率在1年时为0.85%，3年时为3.6%，5年时为5.4%。相应的估计短暂性脑缺血发作累积发生率分别为1.9%、5.5%和6.3%。狭窄进展的相应估计累积发生率分别为4.9%、16.7%和26.5%。同侧卒中的生命表比较显示，狭窄程度进展的动脉累积发生率显著高于保持稳定的动脉（p<0.001）。
基于这些病例中永久性神经事件的低发生率，目前不建议对无症状的中度狭窄颈内动脉进行预防性颈动脉内膜切除术。唯一似乎能预测未来卒中风险增加的因素是狭窄进展。必须对这些患者进行仔细的随访并进行系列重复双功超声检查。在有被广泛接受的双功超声参数，能为所有临床医生提供准确识别符合无症状颈动脉粥样硬化研究定义的60%狭窄的狭窄动脉之前，所有外科医生都需要特别了解他们的无创实验室是如何得出结果的。对于许多仍在使用华盛顿大学标准的实验室，80%应仍是有必要进行预防性颈动脉内膜切除术的狭窄水平。
