Hemodynamic Impact of Stenting on Carotid Bifurcation: A Potential Role of the Stented Segment and External Carotid Artery.

Carotid stenting near the bifurcation carina is associated with adverse events, especially in-stent restenosis, thrombosis, and side branch occlusion in clinical data. This study is aimed at determining the potential biomechanical mechanisms for these adverse events after carotid stenting. The patient-specific carotid models were constructed with different stenting scenarios to study the flow distribution and hemodynamic parameters, such as wall shear stress (WSS), flow velocity, relative residence time (RRT), and oscillating shear index (OSI) in the carotid bifurcation. The results suggested that the existing stents surely reduced blood flow to the external carotid artery (ECA) but enhanced local flow disturbance both in ECA and stented internal carotid artery (ICA), and the inner posterior wall of the stented ICA and the outer posterior wall of ECA might endure a relatively low level of WSS and remarkably elevated OSI and RRT. In addition, the implanted stent leads to more ECA adverse flow than ICA after stenting. While disturbed flow near the strut increased as stent length increased, blood flow and areas of local flow disturbance in ECA slightly decreased as stent length increased. In conclusion, the results revealed that ECA might be in relatively high levels of abnormal local hemodynamics after stenting, followed by stented ICA, leading to potential adverse events after intervention.

Carotid ultrasonography predicts collateral development following combined direct and indirect revascularization surgery in adult ischemic Moyamoya disease.

OBJECTIVE: The relationship between carotid ultrasonographic parameters and postoperative collateral development in adult ischemic moyamoya disease (MMD) patients who received combined direct and indirect revascularization surgery remains unclear. Herein, we investigated the postoperative changes in carotid ultrasonographic parameters in patients with adult ischemic MMD. METHODS: We studied 28 adult ischemic MMD patients (31 hemispheres) who underwent combined revascularization surgery. Patients underwent preoperative and postoperative (within 14 days and 3, 12, and 24 months after surgery) magnetic resonance imaging and carotid ultrasonography. We defined the hemisphere in which all signal intensities of the superficial temporal, middle meningeal, and deep temporal arteries were increased compared with that before surgery on magnetic resonance angiography as well-developed collateral establishment. RESULTS: Patients with good collateral establishment on MRA at 2-year after surgery had a lower external carotid artery (ECA) pulsatility index (PI) (P = 0.0413) and ECA/internal carotid artery (ICA) pulsatility index (PI) ratio (P = 0.0427) at 3-month post-operation. At 3-month post-operation, a cut-off ECA PI of 1.416 (sensitivity 40.0 %, specificity 92.3 %, area under the curve 0.7282, likelihood ratio 5.20, P = 0.0404) and ECA/ICA PI ratio of 0.8768 (sensitivity 50.0 %, specificity 92.31 %, area under the curve 0.7308, likelihood ratio 6.50, P = 0.0415) provided reliable values for good prediction of collateral development at 2 years after revascularization. CONCLUSION: ECA/ICA PI ratio and ECA PI at 3-month after surgery can be one of the indicators for predicting future well-developed neovascularization on MRA and better outcome in patients with adult ischemic MMD who received combined direct and indirect revascularization surgery.

Differentiation of dural arteriovenous fistula from reflux venous flow on 3D TOF-MR angiography: identifying asymmetric enlargement of external carotid artery branches.

AIM: To differentiate dural arteriovenous fistula (DAVF) from reflux venous flow (RVF) by assessment of asymmetric enlargement of external carotid artery (ECA) branches on three-dimensional (3D) time-of-flight magnetic resonance angiography (TOF-MRA). MATERIALS AND METHODS: Nineteen patients with DAVF and 27 patients with RVF were included from September 2007 to April 2019. The locations of DAVF were the cavernous (n=9) and sigmoid-transverse (n=6) sinuses, and the jugular (n=3) and sphenoparietal (n=1) veins. Two radiologists visually assessed asymmetric enlargement of the ascending pharyngeal artery (ASP), middle meningeal artery (MMA), accessory meningeal artery (AMA), artery of the foramen rotundum, and occipital artery. MMA size was also measured quantitatively. RESULTS: More frequent asymmetric enlargement of the ASP and MMA were seen in DAVF than in RVF (17 of 19 versus 3 of 27 for ASP; 16 of 19 versus 1 of 27 for MMA, p<0.01). The AMA, artery of the foramen rotundum, and occipital arteries were not visualised in RVF patients. The ipsilateral MMA size was significantly larger in DAVF than in RVF (2.14 versus 0.64 mm2, p< 0.01). The diagnostic performance of ipsilateral MMA size for DAVF was good, with an area under the receiver operating characteristic curve of 0.89, with a sensitivity of 84.2% and a specificity of 81.5% at a cut-off of 1.08 mm2. CONCLUSIONS: DAVF showed significantly larger ECA branches than RVF on 3D TOF-MRA. Therefore, thorough evaluation of ECA branches could help to differentiate DAVF from RVF.

Peak systolic velocity and color aliasing are important in the development of duplex ultrasound criteria for external carotid artery stenosis.

OBJECTIVE: The external carotid artery (ECA) serves as a major collateral pathway for ophthalmic and cerebral artery blood supply. It is routinely examined as part of carotid duplex ultrasound, but criteria for determining ECA stenosis are poorly characterized and typically extrapolated from internal carotid artery data. This is despite the fact that the ECA is smaller in diameter, with a higher resistance and lower volume flow pattern. We hypothesized that using the cutoff of a peak systolic velocity (PSV) ≥125 cm/s, extrapolated from internal carotid artery data, will overestimate the prevalence of ≥50% ECA stenosis and aimed to determine a more appropriate criterion. METHODS: From December 2016 to July 2017, consecutive carotid duplex ultrasound studies performed in our university hospital Intersocietal Accreditation Commission-accredited vascular laboratory were prospectively identified and categorized with respect to prevalence and distribution of ECA PSVs and color aliasing, an indication of turbulent flow or flow acceleration. Presence of color aliasing was determined by two individual reviewers and agreement assessed by Cohen κ coefficient. ECA stenosis was calculated by the North American Symptomatic Carotid Endarterectomy Trial (NASCET) method in patients with computed tomography angiography (CTA) performed within 3 months of carotid duplex ultrasound without an intervening intervention. Receiver operating characteristic analysis was performed to identify best criteria for determining ≥50% ECA stenosis. RESULTS: There were 1324 ECAs from 662 patients analyzed; 174 patients had a total of 252 ECAs with PSV ≥125 cm/s (19% of the total sample). Of those ECAs with PSVs ≥125 cm/s, 30.5% were between 125 and 149 cm/s, 22.2% were between 150 and 174 cm/s, 13.1% were between 175 and 199 cm/s, and 34.1% were ≥200 cm/s. There were 341 ECAs that were analyzed for the presence of color aliasing. In 86 ECAs with PSV ≥200 cm/s, 58.1% had color aliasing, whereas in 255 ECAs with PSV <200 cm/s, only 19.2% had color aliasing (P = .0001). There were 325 CTA studies reviewed and assessed for the presence of a ≥50% ECA stenosis as determined by CTA. Overall, the combination of an ECA PSV ≥200 cm/s with the presence of color aliasing provided the highest combination of sensitivity (90%), specificity (96%), positive predictive value (83%), and negative predictive value (98%) and the greatest area under the curve of 0.971 for determining the presence of a ≥50% ECA stenosis based on CTA. CONCLUSIONS: A PSV ≥125 cm/s alone probably overestimates the prevalence of ≥50% ECA stenosis. A PSV ≥200 cm/s combined with color aliasing is highly predictive of >50% ECA stenosis based on correlation with CTA.

Duplex Criteria for Grading of External Carotid Stenosis.

BACKGROUND: External carotid artery (ECA) stenosis is an independent mortality predictor. Additionally, concomitant ECA and internal carotid artery (ICA) stenosis progression has been associated with an increased risk of ipsilateral ischemic events in asymptomatic patients. Universally accepted ECA duplex velocity criteria, for the prediction of stenosis, do not exist. METHODS: Consecutive patients undergoing angiography and carotid duplex assessments were compared (n = 140). ICA, common carotid artery (CCA), and ECA peak systolic velocities (PSVs) were recorded. ECA/CCA PSV ratio was calculated. These parameters were compared with angiographic ECA measurements. Receiver-operator curve analysis was used to determine optimal criteria in identifying ECA stenosis of >50%. RESULTS: In patients with little ipsilateral ICA disease, for the detection of ECA stenosis of ≥50%, an ECA PSV >148 cm/sec provided a sensitivity of 80%, specificity of 76.2%, and an overall accuracy of 77.1%. An ECA/CCA PSV ratio of 1.45 demonstrated a sensitivity of 73.7%, specificity of 66.7%, and an accuracy of 68.2%.In patients with ICA stenosis ≥50%, for the detection of ECA stenosis of ≥50%, an ECA PSV >179 cm/sec provided a sensitivity of 50%, specificity of 79.6%, and overall accuracy of 71.3%. An ECA/CCA PSV ratio of ≥1.89 provided a sensitivity of 71.9%, specificity of 72.7%, and overall accuracy of 72.5%. CONCLUSIONS: ECA PSV and ECA/CCA PSV ratios appear as useful metrics for the prediction of unilateral high-grade ECA stenosis.

Early hemodynamic characteristics of eversion and patch carotid endarterectomies.

OBJECTIVE: Carotid endarterectomy (CEA) is currently the gold standard in the operative management of carotid artery stenosis. While eversion and patch CEAs vary greatly in technique, various studies have determined equivalence with regard to clinical outcomes. However, the hemodynamic differences following each procedure are not known. This study aimed to investigate any early hemodynamic differences between eversion and patch CEAs. METHODS: All CEAs performed at our institution from March 2012 to June 2018 were aggregated in a retrospective database by querying the 35301 CPT code from the electronic medical record system. Variables collected included gender, age, laterality of CEA, type of procedure, and pre- and post-operative duplex ultrasound (DUS) date and quantitative findings. Exclusion criteria included any procedure with incomplete data, a post-operative DUS > 90 days following the procedure, CEAs with concomitant bypass(es), isolated external carotid artery (ECA) endarterectomies, and re-do CEAs. RESULTS: One hundred and seventy-one CEAs were performed in 161 unique patients. There were 101 males and 60 females, with an average age of 69.7 (38-96; ± 9.36). 63 CEAs were excluded from analysis: 51 due to incomplete data, eight with a > 90 day post-operative DUS, 2 isolated ECA endarterectomies, 1 CEA with a carotid-subclavian bypass, and 1 re-do CEA secondary to an infected patch. Twenty-seven eversion and 81 patch CEAs were included in analysis. There was no difference in procedure laterality or gender between the two cohorts (p > 0.05); however, patients who received an eversion CEA were older on average (73.3 vs 67.5; p = 0.002). Pre-operative peak systolic velocities (PSV) of the proximal internal carotid artery (ICA), distal ICA, and distal common artery (CCA) were all similar (p > 0.05). Post-operative DUS was performed at 17.0 and 12.9 days in the eversion and patch CEA cohorts, respectively (p = 0.12). Post-operative PSV and change in PSV were similar for all three aforementioned segments (p > 0.05). CONCLUSION: Although eversion and patch CEAs vary greatly in technique and post-procedure anatomy, there was no significant difference in post-operative PSV or change in PSV at or around the carotid bifurcation.

Impact of external carotid artery occlusion at declamping of the external and common carotid arteries during carotid endarterectomy on development of new postoperative ischemic cerebral lesions.

OBJECTIVE: The external carotid artery (ECA) is inadvertently occluded during carotid endarterectomy (CEA). The importance of ECA occlusion has been emphasized as a loss of extracranial to intracranial collaterals, a source of chronic embolization, or a site for extended thrombosis during wound closure. This study aimed to determine whether ECA occlusion that inadvertently developed during endarterectomy and that was eventually detected using blood flow measurement of the ECA after declamping of all carotid arteries is a risk factor for development of new postoperative ischemic lesions at declamping of the ECA and common carotid artery (CCA) while clamping the internal carotid artery (ICA). This study also aimed to determine whether intraoperative transcranial Doppler (TCD) monitoring predicts the risk for development of such lesions. METHODS: This was a prospective observational study that included patients undergoing CEA for severe stenosis (≥70%) of the cervical ICA. When blood flow through the ECA measured using an electromagnetic flow meter decreased rapidly on clamping of only the ECA before carotid clamping for endarterectomy and was not changed by clamping of only the ECA after carotid declamping following endarterectomy, the patient was determined to have developed ECA occlusion. These patients underwent additional endarterectomy for the ECA. TCD monitoring in the ipsilateral middle cerebral artery was also performed throughout surgery to identify microembolic signals (MESs). Brain magnetic resonance diffusion-weighted imaging (DWI) was performed before and after surgery. RESULTS: There were 104 patients enrolled in the study. Eight patients developed ECA occlusion during surgery. The incidence of intraoperative ECA occlusion was significantly higher in patients without MESs at the phase of ECA and CCA declamping (8/12 [67%]) than in those with MESs (0/92 [0%]; P < .0001). Six patients exhibited new postoperative ischemic lesions on DWI. The incidence of intraoperative ECA occlusion (P < .0001) and the absence of MESs at declamping of the ECA and CCA while clamping the ICA (P <. 0001) were significantly higher in patients with development of new postoperative ischemic lesions on DWI than in those without. Sensitivity and specificity for the absence of MESs at declamping of the ECA and CCA while clamping the ICA for predicting development of new postoperative ischemic lesions on DWI were 100% (6/6) and 94% (92/98), respectively. CONCLUSIONS: ECA occlusion at declamping of the ECA and CCA while clamping the ICA during CEA is a risk factor for development of new postoperative ischemic lesions. Intraoperative TCD monitoring accurately predicts the risk for development of such lesions.

Ocular Blood Flow in Rabbits under Deep Anesthesia: A Real-Time Measurement Technique and Its Application in Characterizing Retinal Ischemia.

In this study, we reported a new technique based on laser speckle flowgraphy to record the ocular blood flow in rabbits under deep anesthesia, and proposed parameters to characterize retinal ischemia. We applied the proposed technique to study the correlation of blood flow between the eyes of normal non-anesthetized animals, and to characterize the occlusion of the internal carotid artery (ICA) and external carotid artery (ECA). We established a correlation in blood flow between the eyes of non-anesthetized animals, and derived two new parameters, namely, the laterality index and vascular perfusion estimate (VPE). Our experimental results from 16 eyes (of 13 New Zealand white rabbits) showed a reduction in ocular blood flow with a significant decrease in the VPE after the occlusion of the ECA (p < 0.001). A low/minimal effect on blood flow was observed with the occlusion of the ICA. In conclusion, we demonstrated a means for the real-time measurement of the ocular blood flow in rabbits under deep anesthesia by using laser speckle flowgraphy and the VPE as an indicator of successful occlusion. The proposed technique might be applicable in quantifying the efficacy of new drugs and interventions for the treatment of retinal ischemia.

Numerical study on the hemodynamics of patient-specific carotid bifurcation using a new mesh approach.

The definition of a suitable mesh to simulate blood flow in the human carotid bifurcation has been investigated. In this research, a novel mesh generation method is proposed: hexahedral cells at the center of the vessel and a fine grid of tetrahedral cells near the artery wall, in order to correctly simulate the large blood velocity gradients associated with specific locations. The selected numerical examples to show the pertinence of the novel generation method are supported by carotid ultrasound image data of a patient-specific case. Doppler systolic blood velocities measured during ultrasound examination are compared with simulated velocities using 4 different combinations of hexahedral and tetrahedral meshes and different fluid dynamic simulators. The Lin's test was applied to show the concordance of the results. Wall shear stress-based descriptors and localized normalized helicity descriptor emphasize the performance of the new method. Another feature is the reduced computation time required by the developed methodology. With the accurate combined mesh, different flow rate partitions, between the internal carotid artery and external carotid artery, were studied. The overall effect of the partitions is mainly in the blood flow patterns and in the hot-spot modulation of atherosclerosis-susceptible regions, rather than in their distribution along the bifurcation.

Cerebral Protection with a Temporary Ascending Aorta-External Carotid Artery Bypass during Common Carotid Artery Revascularization.

Atherosclerosis is a systemic disease, and multiarterial involvement is common. Involvement of all the supra-aortic arteries may occur in the same patient making cerebral revascularization challenging. In this report, we present complete supra-aortic revascularization, that is, revascularization of the bilateral common carotid and subclavian arteries in a 51-year-old male patient with occluded brachiocephalic trunk, left subclavian artery, and proximally stenotic left common carotid artery. A temporary ascending aorta to left external carotid artery bypass provided meticulous cerebral protection with pulsatile cerebral flow in the presence of a proximal arterial clamp; hence, a neurologically uneventful procedure during bilateral common carotid artery revascularization.

Dynamic Cerebral Autoregulation Assessment Using Extracranial Internal Carotid Artery Doppler Ultrasonography.

Transcranial Doppler ultrasonography of the middle cerebral artery (MCA) is frequently used to assess dynamic cerebral autoregulation (dCA); however, this is difficult in patients with poor temporal bone windows. In the study described here, we investigated the agreement and sensitivity of dCA indices determined from the extracranial internal carotid artery (ICA) and those determined from the MCA. Measurements for 32 stroke patients and 59 controls were analyzed. Measurement of the mean flow correlation index (Mx) and transfer function analysis based on spontaneous blood pressure fluctuation were simultaneously performed for the extracranial ICA and MCA. The mean values of Mx and phase shift did not significantly differ between the ICA and MCA (mean difference: Mx = 0.01; phase shift of very low frequency [VLF] = 0.7°, low frequency [LF] = 3.3° and high frequency = 4.5°), but the gains in VLF and LF in the ICA were significantly lower than those in the MCA (mean difference: gain of VLF = -0.13, gain of LF = -0.10). The intra-class correlation coefficient between the dCA indices of the ICA and MCA was favorable in Mx (0.76) and the phase shift of VLF (0.72). The area under the receiver operating characteristic curve for stroke diagnosis did not differ among the dCA indices. We conclude that dCA assessed from the ICA is as effective as that from the MCA, but the results are not interchangeable.

Predictive Role of External Carotid Artery Vasospasm on Cerebral Ischemia After Subarachnoid Hemorrhage: Experimental Study.

AIM: Cerebral vasospasm after subarachnoid hemorrhage (SAH) may lead to a devastating neurological outcome by inducing cerebral ischemia. However the role of external carotid artery (ECA) vasospasm has been rarely reported in the literature. The aim of this study was to elucidate the effect of ECA vasospasm on cerebral ischemia related neurodegeneration in the cerebral cortex after SAH. MATERIAL AND METHODS: This study was performed on 23 rabbits, divided into three groups: control (n=5), sham (n=5), and SAH (n=13). Experimental SAH was performed by injecting 0.75 mL auricular arterial homologous blood into the cisterna magna. After three weeks, the animals were decapitated and the common carotid arteries with their external and internal branches and the brains were examined histopathologically. Vasospasm indexes (VSI) of ECAs and internal carotid arteries (ICAs) and degenerated glial cell numbers of temporal cortices (n/mm3) were estimated stereologically and the results were compared statistically. RESULTS: Temporal cortex glial cell density was estimated as 136.950±9.257/mm3 in normal rabbits, 131.324±7.987/mm3 in sham, 112.320±6.112/mm3 in light, and 97.543±5.432/mm3 in severe ECA vasospasm. The mean VSI values of ECA of all groups were 1.95±0.21, 2.15±0.29, 2.95±0.65 and 3.12±0.276, respectively. Statistical differences between the VSI values of ECA and degenerated neuron densities in temporal cortices were significant (p < 0.005). CONCLUSION: ECA vasospasm was observed to have a more important predictive role on the serious cerebral ischemia and neuronal degeneration after SAH. The mechanism may be related to ischemia of the parasympathetic ganglia of the lower cranial nerves and dorsal root ganglion.

Mastication Steal Syndrome.

A 56-year-old woman presented with episodic vertigo, dizziness, and diplopia during meals and prolonged verbal presentations at work. Subsequent work-up included an eventual catheter-based angiogram revealing an ostial left external carotid artery (ECA) occlusion with reconstituted retrograde flow via a variant collateral branch from the dominant left vertebral artery. The findings demonstrate that repetitive activities involving craniofacial muscular systems supplied by the ECA result in a symptomatic arterial steal syndrome via the enhanced diverted flow from the collateral vertebral-basilar arterial system. A left ECA endarterectomy with reimplantation of the vessel was performed, and the patient has been episode free thereafter.

Differential Regulation of BMAL1, CLOCK, and Endothelial Signaling in the Aortic Arch and Ligated Common Carotid Artery.

The circadian clock is rhythmically expressed in blood vessels, but the interaction between the circadian clock and disturbed blood flow remains unclear. We examined the relationships between BMAL1 and CLOCK and 2 regulators of endothelial function, AKT1 and endothelial nitric oxide synthase (eNOS), in vascular regions of altered blood flow. We found that the aortic arch from WT mice exhibited reduced sensitivity to acetylcholine (Ach)-mediated relaxation relative to the thoracic aorta. In Clock-mutant (mut) mice the aorta exhibited a reduced sensitivity to Ach. In WT mice, the phosphorylated forms of eNOS and AKT were decreased in the aortic arch, while BMAL1 and CLOCK expression followed a similar pattern of reduction in the arch. In conditions of surgically induced flow reduction, phosphorylated-eNOS (serine 1177) increased, as did p-AKT in the ipsilateral left common carotid artery (LC) of WT mice. Similarly, BMAL1 and CLOCK exhibited increased expression after 5 days in the remodeled LC. eNOS expression was increased at 8 p.m. versus 8 a.m. in WT mice, and this pattern was abolished in mut and Bmal1-KO mice. These data suggest that the circadian clock may be a biomechanical and temporal sensor that acts to coordinate timing, flow dynamics, and endothelial function.

Long-Term Follow-Up for a Giant Basilar Trunk Aneurysm Surgically Treated by Proximal Occlusion and External Carotid Artery to Posterior Cerebral Artery Bypass Using a Saphenous Vein Graft.

The authors describe a case of a basilar trunk aneurysm with long-term follow-up after successful bypass and proximal occlusion. A 64-year-old woman had a giant aneurysm of the basilar trunk and underwent external carotid artery-to-posterior cerebral artery vein graft bypass surgery and proximal clipping of the basilar artery, which was followed by low-dose aspirin (100 mg/d) treatment. No ischemic symptoms and lesions developed and the thrombosed aneurysm was stable during 11 years of follow-up. An extracranial-intracranial high flow bypass combined with immediate proximal occlusion and aspirin administration may be an acceptable treatment option for patients with giant posterior circulation aneurysms.

Development of a Duplex Ultrasound Simulator and Preliminary Validation of Velocity Measurements in Carotid Artery Models.

OBJECTIVE: Duplex ultrasound scanning with B-mode imaging and both color Doppler and Doppler spectral waveforms is relied upon for diagnosis of vascular pathology and selection of patients for further evaluation and treatment. In most duplex ultrasound applications, classification of disease severity is based primarily on alterations in blood flow velocities, particularly the peak systolic velocity (PSV) obtained from Doppler spectral waveforms. We developed a duplex ultrasound simulator for training and assessment of scanning skills. METHODS: Duplex ultrasound cases were prepared from 2-dimensional (2D) images of normal and stenotic carotid arteries by reconstructing the common carotid, internal carotid, and external carotid arteries in 3 dimensions and computationally simulating blood flow velocity fields within the lumen. The simulator displays a 2D B-mode image corresponding to transducer position on a mannequin, overlaid by color coding of velocity data. A spectral waveform is generated according to examiner-defined settings (depth and size of the Doppler sample volume, beam steering, Doppler beam angle, and pulse repetition frequency or scale). The accuracy of the simulator was assessed by comparing the PSV measured from the spectral waveforms with the true PSV which was derived from the computational flow model based on the size and location of the sample volume within the artery. RESULTS: Three expert examiners made a total of 36 carotid artery PSV measurements based on the simulated cases. The PSV measured by the examiners deviated from true PSV by 8% ± 5% (N = 36). The deviation in PSV did not differ significantly between artery segments, normal and stenotic arteries, or examiners. CONCLUSION: To our knowledge, this is the first simulation of duplex ultrasound that can create and display real-time color Doppler images and Doppler spectral waveforms. The results demonstrate that an examiner can measure PSV from the spectral waveforms using the settings on the simulator with a mean absolute error in the velocity measurement of less than 10%. With the addition of cases with a range of pathologies, this duplex ultrasound simulator will be a useful tool for training health-care providers in vascular ultrasound applications and for assessing their skills in an objective and quantitative manner.

Computational fluid dynamics analysis of tandem carotid artery stenoses: Investigation of neurological complications after carotid artery stenting.

BACKGROUND: Combined extra- and intracranial carotid artery stenoses, particularly involving multiple lesions, show complex hemodynamic properties and represent a therapeutic dilemma. We used computational fluid dynamics (CFD) to investigate whether insufficient cerebral blood flow (CBF) in a 70-year-old man with tandem stenoses was the cause of aphasia and right hemiparesis after carotid artery stenting (CAS) of the extracranial stenosis. METHOD: Three-dimensional digital subtraction angiography (3D-DSA) was performed before and after balloon angioplasty and CAS in the patient. The geometrical and rheological conditions of the carotid arteries were determined, and computational meshes were generated from the patient-specific 3D-DSA datasets. CFD analysis was performed, and hemodynamic parameters such as mass flow, pressure, fractional flow reserve, and streamlines were calculated. RESULTS: Post-CAS simulations showed that the percentage of internal carotid artery mass flow from common carotid artery mass flow increased from 9% to 14% and CBF improved by only 5%. CONCLUSIONS: CFD analysis suggested that the neurological complications were caused by insufficient CBF rather than embolic events, and in tandem carotid stenoses, CAS for an extracranial lesion alone may not always sufficiently increase CBF. CFD enabled the noninvasive quantitative estimation of the effects of CAS of each stenotic segment on carotid flow.

Dynamic cerebral autoregulation is unrelated to decrease in external carotid artery blood flow during acute hypotension in healthy young men.

NEW FINDINGS: What is the central question of this study? Dynamic cerebral autoregulation (CA) is impaired by sympathetic blockade, and the external carotid artery (ECA) vascular bed may prevent adequate internal carotid artery blood flow. We examined whether α1 -receptor blockade-induced attenuation of dynamic CA is related to reduced ECA vasoconstriction. What is the main finding and its importance? α1 -Receptor blockade attenuated dynamic CA, but in contrast to our hypothesis did not affect the ECA blood flow response to acute hypotension. These findings suggest that the recovery of cerebral blood flow during acute hypotension is unrelated to vasoconstriction within the ECA territory. External carotid artery (ECA) vasoconstriction may defend internal carotid artery (ICA) blood flow during acute hypotension. We hypothesized that the α1 -receptor blockade-induced delay in ICA recovery to the baseline level from acute hypoperfusion is related to attenuated ECA vasoconstriction. The ICA and ECA blood flow were determined by duplex ultrasound during thigh-cuff release-induced acute hypotension while the α1 -receptor blocker prazosin [1 mg (20 kg)(-1) ] was administered to nine seated young healthy men. Both ICA (mean ± SD; by 17 ± 8%, P = 0.005) and ECA (by 37 ± 15%, P < 0.001) blood flow decreased immediately after occluded thigh-cuff release, with a more rapid ICA blood flow recovery to the baseline level (9 ± 5 s) than for the ECA blood flow (17 ± 5 s; P = 0.019). The ICA blood flow recovery from hypoperfusion was delayed with prazosin (17 ± 4 s versus control 9 ± 5 s, P = 0.006), whereas ECA recovery remained unchanged (P = 0.313) despite a similar reduction in mean arterial pressure (-20 ± 4 mmHg versus control -23 ± 7 mmHg, P = 0.148). These findings suggest that α1 -receptor blockade-induced attenuation of the ICA blood flow response to acute hypotension is unrelated to the reduction in ECA blood flow. The sympathetic nervous system via the ECA vascular bed does not contribute to dynamic CA during acute hypotension.

Elliptical transection for eversion endarterectomy enables efficient external carotid artery desobliteration.

BACKGROUND: Eversion endarterectomy (EEA) of the internal carotid artery requires less distal surgical exposure than conventional patch reconstruction endarterectomy. However, the technical success after EEA was tremendously contradictive especially with respect to the external carotid artery (ECA) patency rate. The purpose of this study was to determine the effect of elliptical EEA on the quality and outcome of external carotid artery desobliteration. METHODS: Clinical outcome and carotid disease progression at one year were evaluated in thirty patients receiving EEA through short transverse skin incision either in general anesthesia (GA, 22 patients) or locoregional anesthesia (LRA, 8 patients). RESULTS: One patient (GA group) required early revision for bleeding. There was no postoperative stroke, nerve damage or death. At one year, ipsilateral systolic peak velocity (SPV) measurements showed no disease progression in the internal (75.30±19.31; 62.88±28.51 cm/s) or in the external carotid artery (118.92±58.30; 79.00±27.15 cm/s, GA; RLA, respectively). The incidence of ipsilateral ECA stenosis >50% decreased from 64% preoperatively to 16 % at one year (P<0.001). On the contralateral side, incidence of ECA stenosis >50% increased from 27% preoperatively to 56% after one year (p=0.018). On the ipsilateral side, all patients in the RLA group had less than 50% stenosis of ECA at one year after the operation (P=0.021 vs. pre-OP), while in the GA group four patients developed 50-74% stenosis and one patient >75% stenosis of ECA (P<0.001 vs. pre-OP). These results were not significantly different between the two groups and demonstrated a total of 96.7% ECA patency at one year. CONCLUSIONS: Elliptical transsection for EEA enables outstanding ECA revascularization with good patency at one year. Type of anesthesia does not affect the quality of the eversion technique.

Circulating miR-21 and eNOS in subclinical atherosclerosis in patients with hypertension.

OBJECTIVES: The aim of this study is to evaluate the relationship of miR-21, nitric oxide (NOx) and endothelial nitric oxide synthase (eNOS) with subclinical atherosclerosis in carotid arteries by measuring carotid intima media thickness (CIMT) in patients with hypertension and healthy controls. DESIGN AND METHODS: A total of 28 hypertensive and 28 healthy controls were enrolled. MiR-21 expression was analyzed by quantitative reverse transcription-PCR and NOx, and eNOS levels were measured by ELISA assay. CIMT was evaluated by ultrasonography and CIMT ≥ 0.8 mm was accepted as increased CIMT (iCIMT). RESULTS: C-reactive protein (CRP) level, plasma miR-21 expression level and CIMT were found to be significantly higher in the hypertension group when compared to the control group (p = 0.009, p = 0.002 and p < 0.001, respectively). NOx and eNOS levels were significantly lower in the hypertension group compared to the control group (p < 0.001, both). MiR-21 level was positively correlated with the clinical systolic blood pressure, clinical diastolic blood pressure, CRP and CIMT. MiR-21 was also negatively correlated with NOx and eNOS. Eighteen patients with hypertension had iCIMT. MiR-21 and CRP levels were significantly higher (p < 0.001 and p = 0.001), whereas NOx and eNOS levels were significantly lower in patients with iCIMT (p < 0.001, both). CONCLUSION: The decreased levels of NOx and eNOS found in this study indicate the co-existence of endothelial dysfunction and hypertension once more. In the absence of microalbuminuria, the increased miR-21 expression in patients with iCIMT made us conclude that this miRNA might be involved in the early stages of atherosclerotic process in hypertensive patients.