AlMuhanna Khalid, Zhao Limin, Kowalewski Gregory, Beach Kirk W, Lal Brajesh K, Sikdar Siddhartha
Electrical and Computer Engineering Department, and Bioengineering Department, George Mason University, Fairfax, VA 22030, USA. kalmuha1@ gmu.edu
Annu Int Conf IEEE Eng Med Biol Soc. 2012;2012:5618-21. doi: 10.1109/EMBC.2012.6347268.
Stroke is the second leading cause of death in the world, and one of the major causes of disability. Approximately 30% of ischemic strokes are due to plaque rupture in the carotid arteries. The most popular diagnostic method uses Doppler ultrasound to find the percent stenosis. However, other factors, such as the hemodynamics around the plaque may play a larger role in identifying the risk of plaque rupture. It has been shown previously in simulations that non-collateral flow in the circle of Willis (COW) could cause an increase of the intraluminal velocity around carotid plaque. This added strain may increase the vulnerability of the plaque to rupture. We investigated asymmetries in flow waveforms in the middle cerebral artery (MCA) in asymptomatic patients with carotid artery stenosis. We compared clinical results of velocity waveforms in the MCA, acquired using transcranial Doppler (TCD), with a simple linear simulation model of the intra- and extracranial arterial network to investigate the relationship between contralateral and ipsilateral flow profiles in the MCA for patients with asymptomatic carotid stenosis. In 17 out of 23 patients we found waveforms consistent with those predicted for a collateralized COW, with minimal differences in delay, velocity magnitude and resistivity index. In 6 cases, some unexpected findings were noted, such as large delays for 2 patients ≤ 50% stenosis, and a large velocity difference with low delay for 4 patients. More studies are needed to elucidate the role of incomplete intracranial collateralization on the hemodynamics around carotid plaque and to use imaging of the COW to corroborate our results.
中风是全球第二大致死原因，也是导致残疾的主要原因之一。约30%的缺血性中风是由颈动脉斑块破裂引起的。最常用的诊断方法是使用多普勒超声来测定狭窄百分比。然而，其他因素，如斑块周围的血流动力学，可能在识别斑块破裂风险方面发挥更大作用。先前的模拟研究表明， Willis环（COW）中的非侧支血流可导致颈动脉斑块周围管腔内流速增加。这种额外的压力可能会增加斑块破裂的易损性。我们研究了无症状颈动脉狭窄患者大脑中动脉（MCA）血流波形的不对称性。我们将经颅多普勒（TCD）获取的MCA中流速波形的临床结果与颅内和颅外动脉网络的简单线性模拟模型进行比较，以研究无症状颈动脉狭窄患者MCA中对侧和同侧血流剖面之间的关系。在23例患者中的17例中，我们发现波形与预测的侧支化COW波形一致，延迟、流速大小和阻力指数差异极小。在6例患者中，发现了一些意外情况，如2例狭窄≤50%的患者延迟时间较长，4例患者延迟时间短但流速差异较大。需要更多研究来阐明颅内侧支循环不完整对颈动脉斑块周围血流动力学的作用，并利用COW成像来证实我们的结果。
