Enhanced external counterpulsation is a Food and Drug Administration-approved, non-invasive, assisted circulation therapy for ischemic cardiovascular and cerebrovascular diseases. Previous studies have confirmed that EECP stimulation induces largely different cerebral hemodynamic responses in patients with ischemic stroke and healthy controls. However, the underlying mechanisms remain uncertain. We hypothesize that different blood redistributions at the carotid bifurcation may play a key role. Ten subjects were enrolled in this study, namely, five patients with neurological disorders and five young healthy volunteers as controls. Magnetic resonance angiography (MRA) was performed on the carotid artery. All the subjects received a single session of EECP treatment, with external cuff pressures ranging from 20 to 40 kPa. Vascular ultrasound measurements were taken in the common carotid artery (CCA), external carotid artery (ECA) and internal carotid artery (ICA). Three-dimensional patient-specific numerical models were developed to calculate the WSS-derived hemodynamic factors. The results indicated that EECP increased CCA and ECA blood flow in both groups. The ICA blood flow in the patient group exhibited a mean increase of 6.67% during EECP treatment compared with the pre-EECP condition; a mean decrease of 9.2% was observed in the healthy control group. EECP increased the averaged wall shear stress (AWSS) throughout the carotid bifurcation in the patient group; the ICA AWSS of the healthy group decreased during EECP. In both groups, the oscillatory shear index (OSI) in the ICA increased proportionally with external cuff pressure. In addition, the relative resident time (RRT) was constant or slightly decreased in the CCA and ECA in both groups but increased in the ICA. We suggest that the benefits of EECP to patients with neurological disorders may partly result from blood flow promotion in the ICA and increase in WSS at the carotid bifurcation. In the healthy subjects, the ICA blood flow remained constant during EECP, although the CCA blood flow increased significantly. A relatively low external cuff pressure (20 kPa) is recommended as the optimal treatment pressure for better hemodynamic effects. This study may play an important role in the translation of physiological benefits of EECP treatment in populations with or without neurological disorders.

OBJECTIVE: To obtain normal ranges for the inner diameters of the carotid arteries.
METHODS: This retrospective analysis included consecutive patients with disease-free carotid arteries who had undergone 3D-DSA at two hospitals in Nanning, Guangxi, between March 2013 and March 2018. Demographic and clinical characteristics, including Essen Stroke Risk Score (ESRS), were extracted from the medical records. The 3D-DSA data were used to calculate the inner diameters of the carotid arteries.
RESULTS: The analysis included 1182 patients (837 males) aged 58.81 ± 11.02 years. The inner diameters of the proximal carotid sinus (CS), CS bulge, distal CS, and common carotid artery (CCA) were larger on the right than on the left (P < 0.05). The inner diameters of the proximal CS, CS bulge, distal CS, and CCA on both sides were larger for males than females (P < 0.05). The inner diameters of the proximal CS, CS bulge, and distal CS on both sides were smaller for patients aged > 65 years than for patients aged ≤ 55 years (P < 0.05). Right CCA inner diameter did not vary with age, whereas left CCA inner diameter was larger for patients aged > 55 years than for patients aged ≤ 45 years (P < 0.05). The inner diameters of the proximal CS, CS bulge, and distal CS on both sides were smaller for patients with ESRS ≥ 3 than those with ESRS < 3 (P < 0.05).
CONCLUSIONS: This study provides reference values for the internal diameters of normal carotid arteries. Carotid artery diameters varied with side, sex, and age.

A patient-specific carotid bifurcation with tandem stenosis found at both internal carotid artery (ICA) and common carotid artery (CCA) was studied. The in vivo pre-carotid endarterectomy (pre-CEA) multi-spectral magnetic resonance imaging (MRI) were performed and in vitro post-CEA carotid plaque tissue sample was collected. MR imaging data and tissue sample staining histology were used to recognize the plaque components. Further, the computational fluid dynamics (CFD) were performed on four MR-based reconstructed 3D carotid bifurcation models (the patient-specific geometry with tandem stenosis and three presumptive geometries by removing the stenosis part). The flow and shear stress behavior affected by the tandem stenosis was analyzed. From the results of MR segmentation and histology analysis, plaque lipid pool and calcification were found at both ICA and CCA. From the result of CFD simulation, the flow shear stress behavior suggested the tandem stenosis as a more \"dangerous\" situation than a single-stenosis artery. Besides, the CFD results deduced that the stenosis at the CCA location formed initially and led to the subsequent formation of stenosis at ICA. This study suggests that when planning CEA, CFD simulation on the presumptive models could help clinicians to estimate the blood flow behavior after surgery. Particular attention should be paid to the case of tandem stenosis, as the local hemodynamic environment is more complex and treatment of one stenosis may lead to a variation in the hemodynamic loading on the second plaque, which may result in either a higher risk of plaque rupture or restenosis.

BACKGROUND: Many studies have demonstrated that the geometry of the carotid bifurcation enables prediction of blood flow variation associated with atherosclerotic plaque formation. The phase angle between the arterial wall circumferential strain and its instantaneous wall shear stress is known as stress phase angle (SPA). This parameter is used to evaluate hemodynamic factors of atherogenesis. Note that SPA can be numerically computed for the purpose of locating atherosclerosis in different artery geometries. However, there is no experimental data to verify its role in the location of atherosclerosis in different artery geometries. In this study, we use an ultrasonic biomechanical method to experimentally evaluate the role of SPA for locating atherosclerosis in carotid bifurcation.
RESULTS: For carotid anthropomorphic vascular phantom experiments, the SPAs of common carotid arteries (CCAs), external carotid arteries (ECAs) and internal carotid arteries (ICAs) are - 148.53 ± 6.92°, - 153.95 ± 5.11°, and - 238.69 ± 1.72°, respectively. The corresponding SPAs are - 173.47 ± 0.065°, - 115.57 ± 4.83° and - 233.9 ± 8.12° for the polyvinyl alcohol (PVA-c) phantoms. In vivo mouse experiments indicated that the wall shear stress and circumferential strain were out of phase in the ICAs (- 280.08 ± 13.12°) to a greater extent as compared to CCAs (- 141.97 ± 8.03°) and ECAs (- 170.07 ± 9.24°).
CONCLUSIONS: The results suggested that SPA may be a useful indicator to locate the atherosclerosis position in carotid bifurcation.

Surface landmarks in the neck are important for orientations of cervical glands, arteries, veins, nerves, and vertebrae. Recent research suggests some orientations are not correct. What are the cervical landmark orientations in the Chinese population? In this study, two essential cervical anatomy planes, the thyroid cartilage and C7 planes, were assessed in living adult Chinese subjects using computed tomography (CT), and the hyoid, carotid bifurcation, cricoid cartilage, thyroid arteries, and vertebral artery were simultaneously positioned. After excluding patients with distorting pathology, a total of 108 cervical CT scans were examined. The thyroid cartilage plane commonly passed through the C5 (in males) or C4 (in females) vertebral level. The carotid artery bifurcated most commonly at C3 (left) or C4 (right), more than 10 mm above the thyroid cartilage plane bilaterally in most cases. Orientation of the carotid bifurcation according to the body or greater horn of the hyoid was more accurate. The superior thyroid artery was found a finger-breadth below the thyroid cartilage plane, and the inferior thyroid artery in the C7 plane. The inferior border of the cricoid cartilage was most often at C7 (in males) or C6 (in females). The vertebral artery entered the C6 transverse foramen in more than 80% of scans. This reassessment of cervical surface anatomy using modern imaging tools in vivo provides both qualitative and quantitative information for surgeons in clinical practice. Clin. Anat. 30:330-335, 2017. © 2017 Wiley Periodicals, Inc.