Status of the Circle of Willis and Intolerance to Carotid Cross-clamping During Carotid Endarterectomy

Isolated Middle Cerebral Artery Significantly Increases Risk of Postoperative Stroke after Transcarotid Revascularization in Asymptomatic Patients

OBJECTIVE

Limited research has been conducted to demonstrate the safety and efficacy of flow reversal in transcarotid revascularization (TCAR) patients with an ipsilateral isolated middle cerebral artery (iMCA). We hypothesize that an iMCA decreases tolerance to flow reversal and increases the risk of ipsilateral ischemic stroke after TCAR.

METHODS

Clinical data and outcomes for TCAR were prospectively collected through our multihospital single-institution VQI between January 2019 and April 2024. Patient characteristics, imaging, and outcomes were retrospectively reviewed. Symptomatic patients and patients with inadequate intracranial imaging for appropriate CoW assessment were excluded. All anatomical segments of the CoW were evaluated by the same research assistant and radiologist and classified as normal, hypoplastic, or absent. The anterior semicircle and both the ipsilateral and contralateral posterior semicircles were further classified as complete, incomplete, and hypoplastic accordingly. Ipsilateral MCA was defined as isolated (iMCA) if there were incomplete segments in both the anterior semicircle and the ipsilateral posterior semicircle. Patients were then divided into iMCA and non-iMCA groups for comparison. Primary outcome was immediate ipsilateral neurologic event (INE), defined as any TIA or stroke diagnosed within 24 hours of the intervention.

RESULTS

A total of 230 TCARs (218 patients) performed for asymptomatic severe carotid artery stenosis were included in our analysis. Baseline characteristics did not differ significantly between groups (Table I). Median treated lesion length was significantly longer in the non-isolated MCA group at 24 mm compared to 19 mm. After imaging analysis, no patient was found to have a complete CoW. An ipsilateral iMCA was found in 27 cases (11.7% of 230 cases, 12.4% of 218 patients). A total of 4 cases (1.7%) suffered an INE. Cases complicated by INE had significantly longer flow reversal times (13.5 mins vs 9 mins, p=0.0142), but did not differ between iMCA and non-iMCA groups. INE occurred in 3 cases (11.1%) in the iMCA group vs 1 (0.5%) in the non-iMCA group (p=0.005). iMCA was significantly associated with risk of INE on univariable logistic regression (OR 25.3, 95% CI [2.5-252.4], p=0.006).

CONCLUSION

In this retrospective single-center study of 230 patients with asymptomatic carotid artery stenosis undergoing TCAR, an isolated middle cerebral artery significantly increases the risk of postoperative stroke. Our results suggest that comprehensive intracranial imaging should be considered on all patients to optimally assess the CoW anatomy prior to flow reversal. We recommend avoiding flow reversal in this patient population and considering alternative treatment methods such as carotid endarterectomy with shunting or TFCAS.

Understanding perioperative risk determinants in carotid endarterectomy: the impact of compromised circle of Willis morphology on inter-hemispheric blood flow indices based on intraoperative internal carotid artery stump pulse pressure and backflow patterns

Carotid artery stenosis (CAS) often requires surgical intervention through carotid endarterectomy (CEA) to prevent stroke. Accurate cerebrovascular risk assessments are crucial in CEA, as poor collateral circulation can lead to insufficient interhemispheric blood flow compensation, resulting in ischemic complications. Therefore, understanding perioperative risk determinants is vital. This study aims to determine the impact of compromised circle of Willis (CoW) morphology on inter-hemispheric blood flow, focusing on indices based on intraoperative internal carotid artery stump pulse pressure and backflow patterns. In 80 CAS patients who underwent CEA, preoperative CT angiography for CoW was conducted. Patients were categorized into five subgroups based on their CoW anatomy and three additional groups based on intraoperative internal carotid artery (ICA) stump backflow patterns evaluated by the surgeon. Continuous blood pressure signals, including systolic, diastolic, mean, and pulse pressure values, were recorded during the procedure. The relationship between CoW anatomical variants and the systolic and diastolic segments of the averaged pressure waveforms, particularly diastolic pressure decay, was analyzed. The correlation between CoW anatomy and stump backflow intensity was also examined. Significant variability in ICA stump backflow and pressure values was evident across CoW variants. Patients with compromised CoW morphology exhibited weaker backflow patterns and lower ICA stump pulse pressure values, consistent with impaired interhemispheric blood flow. Notably, ICA stump diastolic pressure decay was consistent across most CoW variant groups, indicating developed collateral circulation in cases with CoW anomalies. Thus, impaired CoW integrity is associated with compromised interhemispheric blood flow indices based on intraoperative ICA stump pulse pressure and backflow patterns during CEA. Integrating intraoperative pulse waveform analysis with preoperative CT angiography provides a more detailed assessment of cerebrovascular risk, guiding the selective use of shunts. This combined approach may improve surgical outcomes and patient safety by identifying patients at increased risk of perioperative neurological events due to CoW anomalies.

The diagnostic accuracy of intraoperative near-infrared spectroscopy in carotid artery endarterectomy under general anesthesia: A systematic review with meta-analysis

BACKGROUND

Carotid endarterectomy (CEA) carries a risk of perioperative stroke, particularly during carotid cross-clamping. While neurological monitoring is reliable for patients under regional anesthesia, alternative options are needed for those unsuitable for regional anesthesia. Near-infrared spectroscopy (NIRS) is commonly used during CEA, but its diagnostic accuracy varies, particularly under general anesthesia.

METHODS

A systematic review with meta-analysis was performed to assess the diagnostic accuracy of intraoperative NIRS in detecting clamp-associated hemodynamic cerebral ischemia in patients under general anesthesia. MEDLINE, Google Scholar, and Web of Science were searched for studies that compared NIRS with the occurrence of immediate or early postoperative neurological deficits in patients undergoing CEA under GA. Meta-regression was performed to explore causes of heterogeneity.

RESULTS

A total of 28 studies involving 5729 patients were included. The results show that NIRS has a summary sensitivity of 47.5% and a summary specificity of 90.3% in diagnosing clamp-associated cerebral ischemia under general anesthesia, with an area under the ROC curve (AUC-ROC) of 0.85. The presence of a contralateral carotid occlusion (CCO) increased summary sensitivity while smoking history the presence of CCO and smoking history decreased summary specificity. For postoperative stroke prediction, NIRS has a summary sensitivity of 49.5% and summary specificity of 88.5%, with an AUC-ROC of 0.85.

CONCLUSIONS

NIRS is a specific but not highly sensitive tool for detecting cerebral ischemia during CEA, and its use in combination with more sensitive neuromonitoring methods is recommended, in order to guide intraoperative neuroprotective strategies.

The effect of the collateral cerebrovascular circulation on tolerance to carotid artery cross-clamping and on early outcome after carotid endarterectomy

OBJECTIVE

The Circle of Willis (CoW) serves as the primary source of contralateral blood supply in patients who undergo carotid artery cross-clamping (CC) for carotid endarterectomy (CEA). It has been suggested that the CoW's anatomy influences CEA outcomes. The aim of this study was to evaluate associations between the cerebral collateral circulation, a positive awake test for intraoperative neurologic deficit after carotid CC, and postoperative adverse neurologic events.

METHODS

A systematic review was conducted searching MEDLINE, Cochrane, and Web of Science databases for studies that assessed the cerebral circulation, including CoW variations, using neuroimaging techniques in patients who underwent carotid CC. For the metanalytical incidence, the statistical technique used was weight averaging. Otherwise, descriptive analysis was used due to the excessive heterogeneity of the studies.

RESULTS

Eight publications, seven cohort and one case-controlled study, involving 1313 patients who underwent carotid artery CC under loco-regional anesthesia, were included in the systematic review. The incidence of positive awake test in the cohort studies ranged from 4.4% to 19.7%. Carotid artery CC resulted in positive awake test in 5% to 91% of patients with alterations in the anterior portion and in 27% to 74% with alterations in the posterior portion of the CoW. A positive awake test in patients with contralateral carotid stenosis or occlusion ranged from 5.8% to 45.7%. Contralateral carotid stenosis >70% or occlusion were associated with a positive awake test (P < .001). Patients with incomplete CoW did not have statistically significant correlation with intraoperative neurological deficits after CC. Data were insufficient to evaluate the effect of the collateral circulation on early outcome after CEA.

CONCLUSIONS

In this systematic review, contralateral carotid artery stenosis or occlusion, but not CoW abnormalities, were associated with a positive awake test after carotid artery CC. Further research is needed to evaluate which specific CoW anomaly predicts neurologic deficit after CC and to confirm association between a positive awake test and clinical outcome after CEA.

Central arterial pressure estimation based on two peripheral pressure measurements using one-dimensional blood flow simulation

Aortic pressure can be estimated using one-dimensional arterial flow simulations. This study demonstrates that two peripheral pressure measurements can be used to acquire the central pressure curve through the patient-specific optimization of a set of system parameters. Radial and carotid pressure measurements and parameter optimization were performed in the case of 62 patients. The two calculated aortic curves were in good agreement, Systolic and Mean Blood Pressures differed on average by 0.5 and -0.5 mmHg, respectively. Good agreement was achieved with the transfer function method as well. The effect of carotid clamping is demonstrated using one resulting patient-specific arterial network.

Intolerance to occlusion during carotid artery stenting with proximal protection: causes, mechanisms, treatment and prevention

Periprocedural cerebral microembolization is the most important complication of carotid artery stenting. Among several variables that play a role to reduce this risk, brain protection (proximal vs. distal) plays a pivot role. Data are accumulating in favor of a better performance of proximal vs. distal especially in symptomatic patients and high-risk carotid plaques. A prerequisite for the technique to be safe and effective is the presence of a valid intracranial collateral circulation to compensate for the target vessel hemisphere avoiding patient intolerance. This complication may occur either soon after the common carotid balloon occlusion or slowly developing during the procedure peaking at the stent post-dilation step. While Willis' circle anatomic variants are the most frequent cause of acute intolerance, a mix of anatomic, hemodynamic and patient cerebral condition play a role for the late developing form. Prevention is the best treatment of intolerance through a pre- and procedural imaging with different techniques (CT angiography, NMR angiography, transcranial Doppler assessment, digital subtraction angiography and back pressure monitoring).

The Gupta Perioperative Risk for Myocardial Infarct or Cardiac Arrest (MICA) Calculator as an Intraoperative Neurologic Deficit Predictor in Carotid Endarterectomy

Background: Patients undergoing carotid endarterectomy (CEA) may experiment intraoperative neurologic deficits (IND) during carotid cross-clamping. This work aimed to assess the impact of the Gupta Perioperative Myocardial Infarct or Cardiac Arrest (MICA) risk calculator in the IND. Methods: From January 2012 to April 2021, patients undergoing CEA with regional anaesthesia for carotid stenosis with IND and consecutively control operated patients without IND were selected. A regressive predictive model was created, and a receiver operating characteristic (ROC) curve was applied for comparison. A multivariable dependence analysis was conducted using a classification and regression tree (CRT) algorithm. Results: A total of 97 out of 194 included patients developed IND. Obesity showed aOR = 4.01 (95% CI: 1.66–9.67) and MICA score aOR = 1.21 (1.03–1.43). Higher contralateral stenosis showed aOR = 1.29 (1.08–1.53). The AUROC curve was 0.656. The CRT algorithm differentiated obese patients with a MICA score ≥ 8. Regarding non-obese patients, the model identified the presence of contralateral stenosis ≥ 55% with a MICA ≥ 10. Conclusion: MICA score might play an additional role in stratifying patients for IND in CEA. Obesity was determined as the best discrimination factor, followed by a score ≥ 8. A higher ipsilateral stenosis degree is suggested to have a part in avoiding procedure-related IND. Larger studies might validate the benefit of MICA score regarding the risk of IND.

The safety and efficacy of the Mo.Ma system device for carotid artery stenting: A single-center experience from Taiwan

Background

Proximal protection devices, such as the Mo.Ma system provides better neurological outcomes than the distal filter system in the carotid artery stenting (CAS) procedure. This study first evaluated the safety and efficacy of the Mo.Ma system during CAS in a single tertiary referral hospital from Taiwan. The outcomes of distal vs. proximal embolic protection devices were also studied.

Methods

A total of 294 patients with carotid artery stenosis who underwent the CAS procedure were retrospectively included and divided into two groups: 152 patients in the distal filter system group and 142 patients in the Mo.Ma system. The outcomes of interest were compared between the two groups. The factors contributing to occlusion intolerance (OI) in the Mo.Ma system were evaluated.

Results

The procedure success rates were more than 98% in both groups. No major stroke occurred in this study. The minor stroke rates were 2.8% (4/142) and 4.6% (7/152) in the Mo.Ma system and filter system, respectively (p = 0.419). Patients with hypoalbuminemia significantly predicted the risk of stroke with an odds ratio of 0.08 [95% confidence interval (CI), 0.01–0.68, p = 0.020] per 1 g/day of serum albumin in the filter group. A total of 12 patients developed OI in the Mo.Ma system (12/142, 8%). Low occlusion pressure predicted the occurrence of OI in the Mo.Ma group with the hazard ratios of 0.88 (95% CI: 0.82–0.96) and 0.90 (95% CI: 0.84–0.98) per 1 mmHg of occlusion systolic pressure (OSP) and diastolic pressure (ODP), respectively. We further indicated that patients with an OSP of ≥60 mmHg or an ODP of ≥44 mmHg could tolerate the procedure of occlusion time up to 400 s, while patients with an OSP of <49 mmHg or an ODP of <34 mmHg should undergo the procedure of occlusion time less than 300 s to prevent the occurrence of OI.

Conclusion

We have demonstrated the safety and effectiveness of the Mo.Ma system during CAS in an Asia population. By reducing the occlusion time, our study indicated a lower risk of OI in the Mo.Ma system and proposed the optimal occlusion time according to occlusion pressure to prevent OI during the CAS procedure. Further large-scale and prospective studies are needed to verify our results.

Arterial collateral anatomy predicts the risk for intra-operative changes in somatosensory evoked potentials in patients undergoing carotid endarterectomy: a prospective cohort study

Background

During carotid endarterectomy (CEA), significant amplitude decrement of somatosensory evoked potentials (SEPs) is associated with post-operative neurological deficits.

Objective

To investigate the association between an incomplete circle of Willis and/or contralateral ICA occlusion and subsequent changes in intra-operatively monitored SEPs.

Methods

We performed a retrospective analysis of a single center, prospective cohort of consecutive patients undergoing CEA over a 42-month period after reviewing the collateral arterial anatomy on pre-operative radiological imaging. The primary endpoint was an intra-operative decline in SEPs > 50% compared to the baseline value during arterial cross-clamping. Univariate and multivariate logistic regression analyses were performed to investigate a potential association between contralateral ICA occlusion, incomplete circle of Willis, and subsequent alteration in SEPs.

Results

A total of 140 consecutive patients were included, of which 116 patients (82.9%) had symptomatic carotid stenosis of at least 50% according to the classification used in the North American Carotid Surgery Trial (NASCET) (Stroke 22:711–720, 1991). Six patients (4.3%) showed contralateral ICA occlusion, 22 patients (16%) a missing/hypoplastic anterior communicating artery (Acom) or A1 segment, and 79 patients (56%) a missing ipsilateral posterior communicating artery (Pcom) or P1 segment. ICA occlusion and missing segments of the anterior circulation (missing A1 and/or missing Acom) were associated with the primary endpoint (p = 0.003 and p = 0.022, respectively).

Conclusion

Contralateral ICA occlusion and missing anterior collaterals of the circle of Willis increase the risk of intra-operative SEP changes during CEA. Pre-operative assessment of collateral arterial anatomy might help identifying patients with an increased intra-operative risk.

Red blood cell distribution width is associated with hypoperfusion in carotid endarterectomy under regional anesthesia

BACKGROUND

A subset of patients submitted to carotid endarterectomy under regional anesthesia develop intraoperative neurologic deficit during carotid artery crossclamping related to critical cerebral perfusion, which may be owing to low flow or embolic phenomena. This subgroup is deemed prone to worse outcomes, which highlights its clinical relevance. The main aim of this study was to identify clinical and hematological predictors for intraoperative neurologic deficit. The secondary aim was to evaluate the perioperative prognostic value of postcarotid artery crossclamping manifestations of cerebral ischemia.

METHODS

Between January 2012 to January 2020, patients submitted to carotid endarterectomy under regional anesthesia in a tertiary referral center who presented intraoperative neurologic deficit were prospectively and consecutively included. This group constituted 8% of the total carotid endarterectomy performed in the center during this timeframe. The control group of patients was the subsequent patient submitted to carotid endarterectomy without intraoperative neurologic deficit in a 1:1 ratio. Blood samples were collected before surgery (<2 weeks). Propensity score matching was used to identify well-matched pairs of patients.

RESULTS

A total of 180 patients were included, with 90 (50% of the cohort and 8% of total carotid endarterectomies) presenting intraoperative neurologic deficit associated to clamping. Mean age was 71.4 ± 9.27 years in the study group and 68.8 ± 8.36 years in the control group. The clinical variables presenting significance after multivariate analysis include: age (adjusted odds ratio: 1.04, 5-95% confidence interval, [1.003-1.078]; P = .034), obesity (adjusted odds ratio: 3.537 [1.445-8.658]; P = .006), lower ipsilateral carotid stenosis grade (adjusted odds ratio: 0.725 [0.525-0.997]; P = .049), and higher contralateral carotid stenosis grade (adjusted odds ratio: 1.266 [1.057-1.516]; P = .010). Red cell distribution width coefficient of variation demonstrated statistical significance in predicting intraoperative neurologic deficit with an adjusted odds ratio of 1.394 (1.076-1.805); P = .012. The 30-day stroke rate was significantly higher in the intraoperative neurologic deficit group, with an adjusted odds ratio of 5.13 (5-95% confidence interval [1.058-24.87]; P = .042) after propensity score matching. Postoperative complications (Clavien-Dindo ≥2) were also associated with intraoperative neurologic deficit (after propensity score matching adjusted odds ratio of 2.748 [5-95% confidence interval, 0.976-7.741]; P = .051).

CONCLUSION

In this study, increased red cell distribution width coefficient of variation demonstrated value to predict intraoperative neurologic deficit. Additionally, age, obesity, a lower degree of ipsilateral carotid stenosis, and a higher degree of contralateral carotid stenosis also demonstrated ability to predict intraoperative neurologic deficit. Moreover, intraoperative neurologic deficit was an independent risk factor for 30-day stroke and postoperative complications Clavien-Dindo ≥2.

The Anatomy of the Circle of Willis Is Not a Strong Enough Predictive Factor for the Prognosis of Cross-Clamping Intolerance during Carotid Endarterectomy

Carotid endarterectomy (CEA) is safe and effective in reducing the risk of stroke in symptomatic severe carotid artery stenosis. Having information about cross-clamping (CC) intolerance before surgery may reduce the complication rate. The purpose of this study was to assess the usefulness of magnetic resonance angiography (MRA) and magnetic resonance angiography perfusion (P-MR) in determining the risk of CC intolerance during CEA. Material and methods: 40 patients after CEA with CC intolerance were included in Group I, and 15 with CC tolerance in Group II. All patients underwent MRA of the circle of Willis (CoW), P-MR with or without Acetazolamide; P(A)-MR in the postoperative period. Results: CoW was normal in the MRA in three cases (7.5%) in Group I, and in eight (53%) in Group II. We found P-MR abnormalities in all patients from Group I and in 40% from Group II. Using a calculated cut-off point of 0.322, the patients were classified as CC tolerant with 100% sensitivity or as CC intolerant with 95% specificity. After evaluating P-MR or MRA alone, the percentage of false negative results significantly increased. Conclusion: The highest value in predicting cross-clamping intolerance is achieved by using analysis of P(A)-MR and MRA of the CoW in combination.

Pencil Beam Presaturation Magnetic Resonance Imaging Helps to Identify Patients at Risk for Intolerance to Temporary Internal Carotid Artery Occlusion During Carotid Endarterectomy and Carotid Artery Stenting

BACKGROUND

There has been no effective method to predict ischemic intolerance to temporary internal carotid artery (ICA) occlusion during carotid artery reconstruction. Pencil beam presaturation (BeamSAT) pulse suppresses the flow signal of the target vessel in magnetic resonance angiography (MRA). Applying this method, we constructed ICA-selective MRA images. The aim of this study was to identify patients at risk for ischemic intolerance by ICA-selective MRA.

METHODS

By evaluating flow of anterior communicating artery (Acom) and A1 portion of anterior cerebral artery with ICA-selective MRA and posterior communicating artery (Pcom) with conventional MRA, we investigated associations of these collateral flow patterns with ischemic intolerance and decrease of regional cerebral oxygen saturation.

RESULTS

The study included 58 patients who underwent carotid endarterectomy or carotid artery stenting. Six of 7 patients without Acom flow and Pcom flow demonstrated ischemic intolerance, whereas all patients (n = 51) with Acom and/or Pcom flow demonstrated tolerance. The accuracy of this prediction model according to Acom and Pcom flow patterns for ischemic intolerance was 0.98 (P = 0.01, binomial test). Regional cerebral oxygen saturation decrease after ICA occlusion was significantly larger in patients without Acom flow and Pcom flow (12.0% ± 6.0%) than in patients with Acom flow and Pcom flow (3.0% ± 3.1%, P < 0.01) and in patients with Acom flow but no Pcom flow (2.4% ± 5.2%, P < 0.01).

CONCLUSIONS

These findings support the importance of Acom flow as a collateral route. ICA-selective MRA enables prediction of ischemic intolerance to temporary ICA occlusion during carotid endarterectomy or carotid artery stenting. This method provides valuable information regarding probability of an ischemic complication.

Incomplete circle of Willis is associated with a higher incidence of neurologic events during carotid eversion endarterectomy without shunting

OBJECTIVE

A complete circle of Willis (CoW) is considered an important collateral network to maintain blood flow during cross-clamping in carotid endarterectomy (CEA). The aim of this study was to evaluate the impact of an incomplete CoW with isolated middle cerebral artery (iMCA) on immediate neurologic events (INEs) after CEA.

METHODS

We prospectively collected the clinical data and outcomes of 902 patients who underwent CEA under general anesthesia between 2013 and 2015. All patients had preoperative computed tomography angiography of the extracranial and intracranial cerebral circulation. Indications were asymptomatic (52%) and symptomatic (48%) carotid artery disease. Patients who had CEA with shunt (n = 35) and those with inadequate intracranial imaging to assess CoW were excluded (n = 322) only. Computed tomography angiography images were reviewed retrospectively and independently by two vascular radiologists who were blinded for treatment outcomes. Imaging assessment included the vertebral and carotid circulation and each segment of the CoW, which was classified as normal, hypoplastic (diameter < 0.8 mm) or absent. The ipsilateral MCA was considered isolated if there was an absence of the anterior and posterior communicating branches from the contralateral carotid or posterior circulations. INE was defined as any transient ischemic attack (TIA) and stroke diagnosed immediately after the procedure.

RESULTS

Of the 545 included patients (331 males; mean age, 69 ± 8 years), 12 (2.2%) had a stroke in the postoperative period. There were 20 INEs (8 strokes and 12 TIAs). A complete CoW was rare; it was only detected in 19 patients (3.5%) and an iMCA was found in 34 patients (6.3%). When at least one collateral circulation was complete (in 330 patients), we observed only four INEs (1.2%). Of the 34 patients with an iMCA, 8 (24%) had INE (6 TIAs and 2 strokes). Overall, iMCA was an independent predictor of INEs (odds ratio, 11.12; 95% confidence interval, 3.57-35.87; P < .001). With logistic regression, the model included hypertension, smoking, diabetes, hyperlipidemia, carotid clamping time (minutes), contralateral significant internal carotid artery stenosis of greater than 90%, ipsilateral significant internal carotid artery stenosis of greater than 90%, preoperative symptoms in 6 months, and iMCA; above iMCA only symptomatic patients had significant risk (odds ratio, 3.34; 95% confidence interval, 1.19-9.73; P = .02), whereas all other parameters were not significant.

CONCLUSIONS

An iMCA carries more than a 10-fold higher the risk of INEs after CEA with cross-clamping without shunt protection. In these patients, routine shunting is recommended to prevent INEs.

Multidetector CT angiography of the Circle of Willis: association of its variants with carotid artery disease and brain ischemia

PURPOSE

(1) to estimate the prevalence of Circle of Willis (CoW) variants in patients undergoing carotid endarterectomy, (2) to correlate these variants to controls and (3) cerebral ischemia depicted by computed tomography (CT).

MATERIALS AND METHODS

After Institutional Review Board approval, data of 544 carotid endarterectomy patients (331 males, mean age 69±8 years) and 196 controls (117 males, mean age 66±11 years) who underwent brain CT and carotid CT angiography (CTA) were retrospectively analysed. Two observers independently classified each CoW segment as normal, hypoplastic (diameter <0.8 mm) or non-visualized. Four groups of CoW variants based on the number of hypoplastic/non-visualized segments were correlated with clinical data (ANOVA, χ² and multivariate logistic regression analysis). Intra- and inter-observer agreement was estimated using Cohen κ statistics.

RESULTS

High prevalence of CoW variants (97%) and compromised CoW (81%) was observed in the study group and significant difference was found in the distribution of CoW variants compared to controls (p<0.001), internal carotid artery (ICA) stenosis being the only independent predictor of CoW morphology (p<0.001). Significant correlation was found between CoW configuration and brain ischemia in the study group (p=0.002). ICA stenosis of ≥90% was associated to higher rate of ipsilateral A1 hypoplasia/non-visualization (p<0.001). Intra- and inter-observer agreement was from substantial to almost perfect (Cohen κ=0.75-1.0).

CONCLUSION

Highly variable CoW morphology was demonstrated in patients undergoing endarterectomy compared to controls. Likely compromised CoW in relation to cerebral ischemia was observed in a large cohort of carotid endarterectomy subjects.

KEY POINTS

• CoW variant distribution significantly differed in the study and control groups (p<0.001). • ICA stenosis was the only independent predictor of CoW morphology (p<0.001). • Severely compromised CoW configuration showed significant association with brain ischemia (p=0.002).

Safety of perioperative cerebral oxygen saturation during debranching in patients with incomplete circle of Willis

OBJECTIVES

The consequences of common carotid artery (CCA) cross-clamping during debranching before thoracic endovascular aortic repair are unclear. We examined the safety of a simple CCA cross-clamping procedure under regional cerebral oxygen saturation monitoring (rSO2) in patients with a complete or incomplete circle of Willis (CoW) anatomy.

METHODS

Twenty-eight patients with thoracic aneurysm underwent elective debranching thoracic endovascular aortic repair with bilateral frontal rSO2 monitoring at our institution between January 2012 and October 2015. Before CCA cross-clamping, we maintained a systemic mean arterial pressure of >100 mm Hg with a vasopressor. We recorded the bilateral frontal rSO2 before, during and after CCA cross-clamping.

RESULTS

The CoW was incomplete in 11 (39.3%) patients. Of these, 6 patients had a complication of ischaemic potential. The left frontal rSO2 was <50% in 3 patients but did not fall below 40%. Compared with baseline values (mean ± SD 64.6 ± 6.9%), the left frontal rSO2 showed no significant change perioperatively in those with a complete CoW on the left CCA cross-clamping (during: 61.0 ± 7.9%, P = 0.17; after: 65.1 ± 5.9%, P = 0.09). In patients with an incomplete CoW with ischaemic potential, the left frontal rSO2 did not change significantly after cross-clamping (baseline: 59.8 ± 3.2%, during: 55.5 ± 5.0%; P = 0.10) but increased significantly on declamping (62.8 ± 4.5%, P = 0.023). The extent of the changes in the mean left frontal rSO2 on clamping and declamping decreased and increased by 7.3% and 11.7%, respectively, in patients with an incomplete CoW, when compared with 5.3% and 5.8% in those with a complete CoW (P = 0.65 and 0.31, respectively). No perioperative cerebrovascular events were observed.

CONCLUSIONS

Simple CCA cross-clamping during debranching was safe when arterial pressure was supported and rSO2 was monitored, even with an incomplete CoW and ischaemic potential.

Investigation of circle of Willis variants and hemodynamic parameters in twins using transcranial color-coded Doppler sonography

Morphological and hemodynamic variations of the circle of Willis (CW) may have an important impact on cerebrovascular events. However, the environmental and genetic influence remains unclear. For this reason we studied the variations and hemodynamic parameters of the CW in twins using transcranial color-coded sonography (TCCS). Sixty-four twins, 19 monozygotic (MZ) and 13 dizygotic (DZ) pairs from the Italian Twin Registry (average age 45.0 ± 13.7 years) underwent TCCS and risk factor assessment. We examined CW morphology and recorded peak systolic velocity (PSV), end-diastolic velocity (EDV) and pulsatility index (PI). Raw heritability was determined for hemodynamic parameters, whereas concordance and discordance rates were calculated for CW morphological variants. A normal CW anatomy was observed in the majority of MZ and DZ twins (76.5% and 92.3%, respectively). The most frequent variant was a missing anterior cerebral artery (ACA). There was no significant difference in the prevalence of most CW variants depending on the zigosity. Concordance rates were low regarding the presence of variant CW anatomy both in MZ and DZ groups (0.14 and 0.00, respectively). Women had a significantly higher PI in vertebral arteries (VA) and in the right ACA (p = 0.01, p = 0.02 and p < 0.01, respectively). An inverse correlation was observed between hemodynamic parameters and age. Morphological variants of the CW do not seem to be heritable; they are most likely determined by environmental factors. In contrast, hemodynamic parameters of the CW are moderately heritable and this might have implications in the management and prevention of cerebrovascular diseases.

Low Common Carotid Artery Systolic Occlusion Pressure and Symptomatic Carotid Artery Stenosis Are Associated with Development of Neurologic Intolerance during Proximal Protected Carotid Artery Stenting

Background and Objectives

Neurologic intolerance (NI) is defined as the occurrence of neurological symptoms during carotid artery stenting (CAS). Because NI is inevitable problem, it may be helpful to anticipate its occurrence. So, we studied factors associated with NI during proximal protected CAS.

Methods

We retrospectively analyzed all consecutive patients underwent proximal protected CAS from August 2012 to January 2017.

Results

We included total 123 patients (109 males, 72±8 years old). The total procedure time was 43±12 minutes, and mean occlusion time was 4.8±1.2 minutes. We divided CAS patients into 2 groups according to presence of NI; neurologic tolerance (NT; n=74, 60%) and NI (n=49, 40%) groups. After the univariate analysis, symptomatic carotid artery stenosis (p=0.003), absence of anterior communicating artery (p=0.015) and low common carotid artery occlusion pressure (CCAOP, p<0.001) were associated with NI. After the multivariate analysis, NI was significantly associated with symptomatic carotid artery stenosis (odds ratio [OR], 5.549; p=0.014) and systolic CCAOP≤42 mmHg (OR, 6.461; p<0.001). In NI group, 43 patients (88%) recovered right after the balloon deflation and 2 patients were normalized within 2 hours. However, 1 had major stroke and 3 had minor strokes in 4 patients with persistent NI ≥24 hours.

Conclusions

About 40% showed NI during the CAS. Most of them (88%, 43 of 49 patients) recovered after the balloon deflation, but stroke incidence was significantly higher in NI group. Symptomatic carotid artery stenosis and systolic CCAOP ≤42 mmHg were significantly associated with the development of NI during proximal protected CAS.

The importance of internal carotid artery occlusion tolerance test in carotid endarterectomy under locoregional anesthesia

BACKGROUNDS

Carotid endarterectomy is considered a safe and effective method for preventing stroke in the short and long term in patients with severe carotid stenosis. The internal carotid artery (ICA) occlusion tolerance test was performed to evaluate cerebral tolerance during temporary carotid occlusion, defined as the capacity of the cerebral hemisphere to maintain adequate cerebral blood flow during occlusion of the ICA. Thus, the aim of the present study is to determine the importance of this test in patients undergoing carotid endarterectomy.

METHODS

From August 2008 to May 2015, 115 consecutive patients (39 female, 77 male) were referred for carotid endarterectomy at the Santa Casa de Belo Horizonte by the main author.

RESULTS

Of the 115 patients who participated in the study, 107 were submitted to carotid endarterectomy. Morbi-mortality was 2.7 %. The presence of deficits during the ICA occlusion tolerance test in less than 30 s was associated with the presence of complications. Among the 104 patients who showed no deficits during the test, only one case (0.9 %) presented complications, while among the three cases that showed deficits during the test and who were submitted to carotid endarterectomy, two cases presented complications (p < 0.0001).

CONCLUSIONS

The carotid endarterectomy under locoregional anesthesia is a safe surgical procedure. The internal carotid artery occlusion tolerance test can help identify high-risk patients who have been assigned this treatment.

Locoregional Anesthesia for Carotid Endarterectomy: Identification of Patients with Intolerance to Cross-Clamping

OBJECTIVE

During carotid endarterectomy (CEA), carotid cross-clamping is performed to allow for artery incision and plaque removal. A small subgroup of patients can tolerate carotid occlusion for only a few seconds, if at all, without presenting neurologic deficit. These patients are described as having ''cross-clamp intolerance.'' The purpose of this study was to demonstrate the safety of locoregional anesthesia in identifying patients with cross-clamp intolerance and factors associated with this condition.

METHODS

From August 2008 to May 2010, 115 consecutive patients were submitted to CEA under locoregional anesthesia at the Santa Casa de Belo Horizonte; the procedure was performed by the main author. Patients who showed intolerance to internal carotid artery (ICA) occlusion for <30 seconds were considered to have cross-clamp intolerance.

RESULTS

Among the 115 participating patients, 9.6% (11 patients) showed intolerance to ICA occlusion and developed deficits in <30 seconds (i.e., these patients presented cross-clamp intolerance). The factor that was associated with cross-clamp intolerance was the mean degree of contralateral carotid stenosis, which was 57.5% for those who presented intolerance and 27.8% for those who tolerated ICA occlusion.

CONCLUSION

Locoregional anesthesia is a safe method for identifying patients with cross-clamp intolerance. Patients with cross-clamp intolerance present contralateral stenosis that is greater on average than patients who readily tolerate carotid artery occlusion.

Pre-operative methods to predict need for shunting during carotid endarterectomy

OBJECTIVES

To establish whether pre-operative investigations are able to predict cerebral tolerance to carotid cross clamping during carotid endarterectomy (CEA).

METHODS

A search of the MEDLINE database from 1950 to 2015 was made in combination with manual cross-referencing using the search strategy: ("carotid" [all fields] AND "endarterectomy" [all fields]) AND "preoperative" [all fields]) AND "clamping" [all fields]) AND ("MRA" [all fields] OR "MRI" [all fields] OR "CT" [all fields] OR "CTA" [all fields] OR "EEG" [all fields] OR "Doppler" [all fields] OR "angiography" [all fields]). A total of 20 studies were identified as eligible for inclusion.

RESULTS

3D Time of Flight MRA and acetazolomide stress SPECT imaging have been reported to have a negative predictive value of 96% and 94% respectively for the need for intraoperative shunting during carotid endarterectomy.

CONCLUSIONS

There is some evidence to suggest that pre-operative imaging investigations can reliably identify which patients undergoing CEA will not require carotid shunting for neurological protection. However, this evidence is limited and there is a need for more rigorous studies to be conducted.

Carotid endarterectomy using a "home-constructed" shunt for patients intolerant to cross-clamping

PURPOSES

There is a small minority of patients with occlusive carotid artery disease, who are at high-risk for general anesthesia because of their intolerance to carotid flow blockage, even if only for seconds, without neurologic deficit. Even <30 s of temporary clamping of the carotid arteries to deploy a shunt may prove eventful in this patient group. We define safe carotid endarterectomy after the insertion of a novel shunt that we made from simple medical equipment in this patient population.

METHODS

Among 65 patients who underwent carotid endarterectomy between March 2010 and December 2012, 5 (7.7 %; 3 men and 2 women; age range 56-77 years) could not tolerate carotid clamping. We used an alternative carotid shunt, made by us from simple equipment in our clinic, during surgery for these patients.

RESULTS

Two patients had bilateral lesions and the remainder had unilateral disease. The degree of stenosis ranged from 70 to 95 %. Temporary carotid clamping resulted in neurologic events, such as loss of consciousness in all and tremor in one, in <10 s (range, from immediately to 8 s after clamping). Full neurologic function was regained 15-30 s after releasing the clamps. All of the patients tolerated the procedures well with the support of our novel shunt. Shunt flow was adequate in all patients and no neurologic deterioration occurred after carotid clamping. The mean carotid clamp time was 28.11 ± 14.19 min. There was no mortality and all patients were followed up for a mean period of 9.3 ± 3.6 months, uneventfully.

CONCLUSIONS

An alternative, simple shunt, which is easily constructed in the operating room or clinic, using an angiocatheter, a three-way stopcock, and a serum line can provide adequate cerebral flow and permit safe carotid endarterectomy for those rare patients with carotid artery stenosis, who cannot tolerate even seconds of carotid occlusion.

Carotid endarterectomy versus stenting: Does the flow really change? An Echo-Color-Doppler analysis

To assess potential hemodynamic differences after carotid endarterectomy (CEA) and carotid artery stenting (CAS) and their eventual impact on clinical management. Between July 2012 and October 2013 two groups of 30 patients each referred for CEA or CAS were prospectively enrolled in two tertiary hospital care centers. Pre-procedural imaging assessment of carotid artery disease was performed with Echo-Color-Doppler (ECD) and computed tomography angiography (CTA). ECD was repeated within 24 h and 1, 6 and 12 months after surgical/endovascular procedures. Peak systolic velocity (PSV) and end diastolic velocity (EDV) were assessed at two standard sites: common carotid artery (CCA) and distal internal carotid artery (ICA). Twenty-four hours ECD findings highly differ between the two populations. CCA PSV in the CEA and CAS groups was respectively 44.88 ± 9.16 and 69.20 ± 20.04 cm/s (p = 0.002); CCA EDV was 16.11 ± 2.29 and 19.13 ± 6.42 cm/s (p = 0.065); ICA PSV was 46.11 ± 7.9 and 94.02 ± 57.7 cm/s (p = 0.0012); ICA EDV was 20.22 ± 4.33 and 30.47 ± 18.33 cm/s (p = 0.025). One month, 6 months and 1 year findings confirmed the different trend in the two cohorts; in particular, at 1 year: CCA PSV was 50.94 ± 12.44 and 60.59 ± 26.84 cm/s (p = 0.181); CCA EDV was 17.11 ± 3.46 and 19 ± 16.35 cm/s (p = 0.634); ICA PSV was 51.66 ± 10.1 and 70.86 ± 20.64 cm/s (p = 0.014); ICA EDV was 25.05 ± 8.65 and 32.66 ± 13 cm/s (p = 0.0609). ECD follow-up of patients undergone CEA or CAS may play a critical role in the clinical management. Strict surveillance of blood flow velocities allows reducing false positive re-stenosis diagnosis and choosing the best anti-aggregation therapies. Within the first month CEA patients benefit from a lower risk condition in comparison with CAS patients, due to a significantly faster PSV drop; moreover, long-term CCA PSV after CEA could be used as a surrogate marker of neointima formation.

Radiographic absence of the posterior communicating arteries and the prediction of cognitive dysfunction after carotid endarterectomy

OBJECT

Approximately 25% of patients exhibit cognitive dysfunction 24 hours after carotid endarterectomy (CEA). One of the purported mechanisms of early cognitive dysfunction (eCD) is hypoperfusion due to inadequate collateral circulation during cross-clamping of the carotid artery. The authors assessed whether poor collateral circulation within the circle of Willis, as determined by preoperative CT angiography (CTA) or MR angiography (MRA), could predict eCD.

METHODS

Patients who underwent CEA after preoperative MRA or CTA imaging and full neuropsychometric evaluation were included in this study (n = 42); 4 patients were excluded due to intraoperative electroencephalographic changes and subsequent shunt placement. Thirty-eight patients were included in the statistical analyses. Patients were stratified according to posterior communicating artery (PCoA) status (radiographic visualization of at least 1 PCoA vs of no PCoAs). Variables with p < 0.20 in univariate analyses were included in a stepwise multivariate logistic regression model to identify predictors of eCD after CEA.

RESULTS

Overall, 23.7% of patients exhibited eCD. In the final multivariate logistic regression model, radiographic absence of both PCoAs was the only independent predictor of eCD (OR 9.64, 95% CI 1.43-64.92, p = 0.02).

CONCLUSIONS

The absence of both PCoAs on preoperative radiographic imaging is predictive of eCD after CEA. This finding supports the evidence for an underlying ischemic etiology of eCD. Larger studies are justified to verify the findings of this study. Clinical trial registration no.: NCT00597883 ( http://www.clinicaltrials.gov ).

Blunt cerebrovascular injury in rugby and other contact sports: case report and review of the literature

Contact sports have long been a part of human existence. The two earliest recorded organized contact games, both of which still exist, include Royal Shrovetide Football played since the 12(th) century in England and Caid played since 1308 AD in Ireland. Rugby is the premier contact sport played throughout the world with the very popular derivative American football being the premier contact sport of the North American continent. American football in the USA has on average 1,205,037 players at the high school and collegiate level per year while rugby in the USA boasts a playing enrollment of 457,983 at all levels. Recent media have highlighted injury in the context of competitive contact sports including their long-term sequelae such as chronic traumatic encephalopathy (CTE) that had previously been underappreciated. Blunt cerebrovascular injury (BCVI) has become a recognized injury pattern for trauma; however, a paucity of data regarding this injury can be found in the sports trauma literature. We present a case of an international level scrum-half playing Rugby Union at club level for a local non-professional team, in which a player sustained a fatal BCVI followed by a discussion of the literature surrounding sport related BCVI.