Department of Vascular and Endovascular Surgery, University of Heidelberg, Heidelberg, Germany.
J Vasc Surg. 2012 Nov;56(5):1403-8. doi: 10.1016/j.jvs.2012.03.035. Epub 2012 May 16.
To assess the influence of stent application on in-stent hemodynamics under standardized conditions.
Ovine common carotid arteries before and after stent (6 × 40 mm, sinus-Carotid-RXt, combined open-closed cell design; Optimed, Ettlingen, Germany) application were used. Plastic tubes, 10 mm in length, simulating stenosis were placed in the middle of the applied stent to induce different degrees of stenosis (moderate 57.8% and severe 76.4%). Flow velocity and dynamic compliance were, respectively, measured with ultrasound and laser scan; proximal, in-stent, and distal to the stented arterial segment (1 cm proximal and distal) in a pulsatile ex vivo circulation system.
Stent insertion caused the in-stent peak systolic velocity to increase 22% without stenosis, 31% with moderate stenosis, and 23% with severe stenosis. Stent insertion without stenosis caused no significant increase in in-stent end-diastolic velocity (EDV) but a 17% increase with moderate stenosis. In severe stenosis, EDV was increased 56% proximal to the stenosis. Compliance was reduced threefold in the middle of the stented arterial segment where flow velocity was significantly increased.
With or without stenosis, stent introduction caused the in-stent peak systolic velocity to become significantly elevated compared with a nonstented area. EDV was also increased by stent insertion in the case of moderate stenosis. The stent-induced compliance reduction may be causal for the increase in flow velocity since the stent-induced flow velocity elevation appeared in the stented area with low compliance. Because of altered hemodynamics caused by stent introduction when measured by duplex ultrasound, caution is prudent in concluding that carotid artery stenting is associated with a higher restenosis rate than carotid endarterectomy. Mistakenly upgrading moderate to severe restenosis could result in unnecessary reintervention.
Clinical experience and prior studies support the supposition that restenosis after carotid artery stenting in carotid lesions displays erroneously elevated velocity when evaluated by duplex ultrasound (DUS), thus contributing to misleading interpretation of the degree of stenosis. This study, in contrast to studies of other groups, employs exactly the same conditions to measure flow with DUS in an unstented and then stented section of the carotid artery. Since DUS is the first-choice tool for carotid artery evaluation, knowledge about inexactness of the method is essential to avoid errors in treatment or follow-up decisions.
在标准化条件下评估支架置入对支架内血流动力学的影响。
使用羊颈总动脉（支架前和支架后，6×40mm，窦颈动脉 RXt，开闭式复合设计；Optimed，Ettlingen，德国）。在应用支架的中间位置放置 10mm 长的塑料管以模拟不同程度的狭窄（中度 57.8%，重度 76.4%）。在脉动式离体循环系统中，使用超声和激光扫描分别测量近端、支架内和支架动脉段（支架近端和远端 1cm 处）的血流速度和动态顺应性。
支架置入后，无狭窄时支架内收缩期峰值速度增加 22%，中度狭窄时增加 31%，重度狭窄时增加 23%。无狭窄时支架置入不会显著增加支架内舒张末期速度（EDV），但中度狭窄时增加 17%。在严重狭窄时，狭窄近端的 EDV 增加 56%。在支架内动脉段中部，血流速度显著增加，顺应性降低至原来的三分之一。
无论是否存在狭窄，支架置入都会导致支架内收缩期峰值速度显著高于非支架区域。中度狭窄时支架置入也会增加 EDV。由于支架引起的顺应性降低可能是导致流速增加的原因，因为支架引起的流速升高出现在顺应性较低的支架区域。由于支架置入引起的血流动力学改变，当通过双功超声测量时，在得出颈动脉支架置入后再狭窄率高于颈动脉内膜切除术的结论时应谨慎。错误地将中度狭窄升级为重度狭窄可能会导致不必要的再次介入。
临床经验和先前的研究支持这样一种假设，即在颈动脉病变中，颈动脉支架置入后的再狭窄在通过双功超声（DUS）评估时显示出错误的流速升高，从而导致对狭窄程度的误解。与其他研究小组的研究不同，本研究采用完全相同的条件在颈动脉未支架和支架后的节段用 DUS 测量血流。由于 DUS 是颈动脉评估的首选工具，因此了解该方法的不准确性对于避免治疗或随访决策中的错误至关重要。
