Interpretation of embolic phenomena during carotid endarterectomy.
Interpretation of embolic phenomena during carotid endarterectomy.
复制标题
颈动脉内膜切除术期间栓塞现象的解释。
作者：
J. Smith;D. Evans;L. Fan;M. Gaunt;N. London;P. Bell;A. Naylor
背景和目的
空气和微粒栓子是颈动脉内膜切除术（CEA）期间发病率的主要来源;然而，振幅过载和时间分辨率差限制了经颅多普勒超声区分两者的能力。
方法
我们现在已经克服了这两个限制，（1）重新路由栓塞信号远离音频放大器，以避免振幅过载和（2）取代维格纳分布函数的快速傅立叶变换，以提高时间和频率分辨率。因此，我们现在可以准确地确定栓塞持续时间和栓塞速度，其产品是样本体积长度（SVL）。该测量值表示可以检测到栓塞信号的物理距离。基本假设是空气反射更多的超声波，因此可以在更大的SVL上检测到。
结果
75例体外空气栓塞的中位SVL（四分位距）为1.97 cm（范围：1.70 - 2.35），而在CEA剥离阶段检测到的185例颗粒栓塞的SVL为0.27 cm（范围：0.16 - 0.43）。对CEA不同阶段检测到的另外560个栓塞信号的离线分析表明，在分流器插入后立即发生的143个栓塞中有46个（32%）是颗粒，在分流期间发生的33个栓塞中有19个（58%），在颈外动脉恢复血流后发生的78个栓塞中有28个（36%），颈内动脉血流恢复后，23/251例（9%），55/55例（100%）在早期恢复阶段检测到栓子。
结论
这一发展提供了客观的物理标准，栓塞表征（颗粒/空气）可以基于此。这可能对未来的患者监测手术技术和药物干预的修改有重大影响。
BACKGROUND AND PURPOSE
Air and particulate emboli are a major source of morbidity during carotid endarterectomy (CEA); however, amplitude overload and poor time resolution have restricted the ability of transcranial Doppler ultrasound to differentiate between the two.
METHODS
We have now overcome these two limitations by (1) rerouting embolic signals away from the audio frequency amplifier to avoid amplitude overload and (2) substituting the Wigner distribution function for the fast Fourier transform to improve time and frequency resolution. Thus, we can now accurately determine embolic duration and embolic velocity, the product of which is the sample volume length (SVL). This measurement represents the physical distance over which an embolic signal can be detected. The underlying hypothesis was that air reflected more ultrasound and would therefore be detected over a greater SVL.
RESULTS
The median SVL (interquartile range) for 75 in vitro air emboli was 1.97 cm (range, 1.70 to 2.35) compared with 0.27 cm (range, 0.16 to 0.43) for 185 particulate emboli detected during the dissection phase of CEA. Off-line analysis on an additional 560 embolic signals detected during different phases of CEA suggested that 46 of 143 (32%) of emboli immediately after shunt insertion were particulate, as were 19 of 33 (58%) occurring during shunting, 28 of 78 (36%) after restoration of flow in the external carotid artery, 23 of 251 (9%) after restoration of flow in the internal carotid artery, and 55 of 55 (100%) of those emboli detected during the early recovery phase.
CONCLUSIONS
This development provides objective physical criteria upon which embolus characterization (particulate/air) can be based. This could have major implications for future patient monitoring with respect to modification of surgical technique and pharmacological intervention.