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.

Quantitative Comparison of Color-Coded Parametric Imaging Technologies Based on Digital Subtraction and Digital Variance Angiography: A Retrospective Observational Study.

The evaluation of hemodynamic conditions in critical limb-threatening ischemia (CLTI) patients is inevitable in endovascular interventions. In this study, the performance of color-coded digital subtraction angiography (ccDSA) and the recently developed color-coded digital variance angiography (ccDVA) was compared in the assessment of key time parameters in lower extremity interventions. The observational study included 19 CLTI patients who underwent peripheral vascular intervention at our institution in 2020. Pre- and post-dilatational images were retrospectively processed and analyzed by a commercially available ccDSA software (Kinepict Medical Imaging Tool 6.0.3; Kinepict Health Ltd., Budapest, Hungary) and by the recently developed ccDVA technology. Two protocols were applied using both a 4 and 7.5 frames per second acquisition rate. Time-to-peak (TTP) parameters were determined in four pre- and poststenotic regions of interest (ROI), and ccDVA values were compared to ccDSA read-outs. The ccDVA technology provided practically the same TTP values as ccDSA (r = 0.99, R2 = 0.98, p < 0.0001). The correlation was extremely high independently of the applied protocol or the position of ROI; the r value was 0.99 (R2 = 0.98, p < 0.0001) in all groups. A similar correlation was observed in the change in passage time (r = 0.98, R2 = 0.96, p < 0.0001). The color-coded DVA technology can reproduce the same hemodynamic data as a commercially available DSA-based software; therefore, it has the potential to be an alternative decision-supporting tool in catheter labs.

Relationship between Gut, Blood, Aneurysm Wall and Thrombus Microbiome in Abdominal Aortic Aneurysm Patients.

Previous research confirmed gut dysbiosis and translocation of selected intestinal bacteria into the vessel wall in abdominal aortic aneurysm patients. We studied the stool, blood, thrombus and aneurysm microbiomes of 21 abdominal aortic aneurysm patients using 16S rRNA sequencing. Our goals were to determine: 1. whether the microbiome characteristic of an aneurysm differs from that of a healthy vessel, 2. whether bacteria detectable in the aneurysm are translocated from the gut through the bloodstream, 3. whether the enzymatic activity of the aneurysm microbiome can contribute to the destruction of the vessel wall. The abundance of Acinetobacter, Burkholderia, Escherichia, and Sphingobium in the aneurysm samples was significantly higher than that in the microbiome of healthy vessels, but only a part of these bacteria can come from the intestine via the blood. Environmental bacteria due to the oral cavity or skin penetration route, such as Acinetobacter, Sphingobium, Enhydrobacter, and Aquabacterium, were present in the thrombus and aneurysm with a significantly higher abundance compared to the blood. Among the enzymes of the microbiome associated with the healthy vessel wall, Iron-chelate-transporting ATPase and Polar-amino-acid-transporting ATPase have protective effects. In addition, bacterial Peptidylprolyl isomerase activity found in the aneurysm has an aggravating effect on the formation of aneurysm.

The Circle of Willis Status Influences Neurological Complications of Carotid Endarterectomy with Contralateral Carotid Occlusion.

BACKGROUND: To evaluate the impact of anatomical variations in the Circle of Willis (CoW) on immediate neurological events (INEs) after carotid endarterectomy (CEA) without shunting in patients with contralateral carotid occlusion (CCO). METHODS: Single-center retrospective study. Patient's demographic and clinical outcomes data were prospectively collected. CoW segments were reviewed retrospectively. Between January 2013 and May 2018, 2090 patients underwent CEA under general anesthesia, CCO was found in 113 (5.4%) patients. CoW segments were classified as normal, hypoplastic (diameter ˂0.8 mm), or absent based on computed tomography angiography. We studied the CoW segments as 2 collateral networks connecting the basilar artery and the ipsilateral middle cerebral artery: a short semicircle (first segment of the ipsilateral posterior cerebral artery [P1] and posterior communicating artery [Pcom] segment) and a long semicircle (contralateral P1, Pcom, and both first segments of the anterior cerebri artery (A1) anterior communicating artery (Acom)). INE was defined as any transient ischemic attack or stroke diagnosed immediately after the procedure. RESULTS: Out of the 113 patients, 46 underwent endarterectomy with shunting. We further excluded 16 patients from the assessment of the CoW due to unavailability or inadequate quality of computed tomography angiography. Of the 113 patients, 2 had strokes, 1 with shunting that occurred hrs after surgery. Besides the other stroke case, 4 INE were observed, all without the use of a shunt. Of the 51 patients with CoW assessment, 10 (19.6%) had a complete CoW, while 21 (41.2%) patients had only 1 semicircle intact (10 short and 11 long intact semicircles), and none of these patients experienced an INE. A total of 20 (39%) patients had both the long and short semicircles incomplete, of which 4 (7.8%) cases had an INE. In all INE cases, at least 1 of the Pcom was absent or hypoplastic. The absence of both Pcom was a strong predictor of incident INE [odds ratio = 11.10 (confidence interval: 1.04-118.60)] for INE. CONCLUSIONS: Patients with CCO and insufficient CoW collateral flow support are at an increased risk of INE, including stroke, in the absence of shunt protection during CEA cross-clamping. Shunting should always be considered when the collateral flow between the ipsilateral middle cerebral artery and the basilar artery is compromised in CCO patients.

Presynaptic Rac1 in the hippocampus selectively regulates working memory.

One of the most extensively studied members of the Ras superfamily of small GTPases, Rac1 is an intracellular signal transducer that remodels actin and phosphorylation signaling networks. Previous studies have shown that Rac1-mediated signaling is associated with hippocampal-dependent working memory and longer-term forms of learning and memory and that Rac1 can modulate forms of both pre- and postsynaptic plasticity. How these different cognitive functions and forms of plasticity mediated by Rac1 are linked, however, is unclear. Here, we show that spatial working memory in mice is selectively impaired following the expression of a genetically encoded Rac1 inhibitor at presynaptic terminals, while longer-term cognitive processes are affected by Rac1 inhibition at postsynaptic sites. To investigate the regulatory mechanisms of this presynaptic process, we leveraged new advances in mass spectrometry to identify the proteomic and post-translational landscape of presynaptic Rac1 signaling. We identified serine/threonine kinases and phosphorylated cytoskeletal signaling and synaptic vesicle proteins enriched with active Rac1. The phosphorylated sites in these proteins are at positions likely to have regulatory effects on synaptic vesicles. Consistent with this, we also report changes in the distribution and morphology of synaptic vesicles and in postsynaptic ultrastructure following presynaptic Rac1 inhibition. Overall, this study reveals a previously unrecognized presynaptic role of Rac1 signaling in cognitive processes and provides insights into its potential regulatory mechanisms.

Linking peripheral atherosclerosis to blood-brain barrier disruption: elucidating its role as a manifestation of cerebral small vessel disease in vascular cognitive impairment.

Aging plays a pivotal role in the pathogenesis of cerebral small vessel disease (CSVD), contributing to the onset and progression of vascular cognitive impairment and dementia (VCID). In older adults, CSVD often leads to significant pathological outcomes, including blood-brain barrier (BBB) disruption, which in turn triggers neuroinflammation and white matter damage. This damage is frequently observed as white matter hyperintensities (WMHs) in neuroimaging studies. There is mounting evidence that older adults with atherosclerotic vascular diseases, such as peripheral artery disease, ischemic heart disease, and carotid artery stenosis, face a heightened risk of developing CSVD and VCID. This review explores the complex relationship between peripheral atherosclerosis, the pathogenesis of CSVD, and BBB disruption. It explores the continuum of vascular aging, emphasizing the shared pathomechanisms that underlie atherosclerosis in large arteries and BBB disruption in the cerebral microcirculation, exacerbating both CSVD and VCID. By reviewing current evidence, this paper discusses the impact of endothelial dysfunction, cellular senescence, inflammation, and oxidative stress on vascular and neurovascular health. This review aims to enhance understanding of these complex interactions and advocate for integrated approaches to manage vascular health, thereby mitigating the risk and progression of CSVD and VCID.

Cerebrovascular dysregulation and postoperative cognitive alterations after carotid endarterectomy.

There are controversial data about the effect of carotid endarterectomy regarding postoperative cognitive function. Our aim was to analyze the effect of cerebral tissue saturation monitored by near-infrared spectroscopy (NIRS) on cognitive function. Perioperative data of 103 asymptomatic patients undergoing elective carotid surgery under general anesthesia were analyzed. Preoperatively and 3 months after the operation, MMSE (Mini Mental State Examination) and MoCA (Montreal Cognitive Assessment) tests were conducted. For cerebral monitoring, NIRS was used, and the lowest rSO2 value and the degree of desaturation were calculated. Cognitive changes were defined as one standard deviation change from the preoperative test scores, defined as postoperative neurocognitive decline (PNCD) and cognitive improvement (POCI). PNCD was found in 37 patients (35.92%), and POCI was found in 18 patients (17.47%). Female gender, patients with diabetes, and the degree of desaturation were independently associated with PNCD. The degree of desaturation during the cross-clamp period negatively correlated with the change in the MoCA scores (R = - 0.707, p = 0.001). The 15.5% desaturation ratio had 86.5% sensitivity and 78.8% specificity for discrimination. For POCI, a desaturation of less than 12.65% had 72.2% sensitivity and 67.1% specificity. POCI was associated with lower preoperative MOCA scores and a lower degree of desaturation. We found a significant relation between the change of postoperative cognitive function proven by the MoCA test and cerebral tissue saturation during the clamping period in patients undergoing carotid endarterectomy.

Comparison of the Snare Loop Technique and the Hungaroring Reinforcement for Physician-Modified Endograft Fenestrations-An In Vitro Study.

BACKGROUND: We conducted an in vitro comparison of the snare loop reinforcement against a closed-loop reinforcement (Hungaroring) for physician-modified endograft (PMEG) fenestrations regarding preparation time and stability during flaring balloon dilatation. MATERIALS AND METHODS: The time to complete a PMEG fenestration with reinforcement was measured and compared between the Hungaroring and snare loop groups. The number of stitches was counted. Each fenestration was dilated using a 10 mm high-pressure, non-compliant balloon up to 21 atm in pressure, and fluoroscopic images were taken. The presence of indentation on the oversized balloon at the level of the reinforcement was evaluated at each fenestration. RESULTS: Five fenestrations were created in each group (n = 5) for a total of ten pieces. The completion time in the snare loop group was 1070 s (IQR:1010-1090) compared to 760 s (IQR:685-784) in the Hungaroring group (p = 0.008). Faster completion time was achieved by faster stitching (23.2 s/stitch (IQR 22.8-27.3) for the snare loop group and 17.3 s/stitch (IQR 17.3-20.1) for the Hungaroring group (p = 0.016). None of the fluoroscopic images of the snare loop reinforcement showed an indentation on the balloon during the overexpansion; on the contrary, the Hungaroring showed indentation in every case, even at 21 atm. CONCLUSION: Fenestrations reinforced with Hungaroring can be completed significantly faster. Furthermore, the Hungaroring resists over-dilation even at high pressures, while snare loop reinforcements dilate at nominal pressure.

Non-Invasive Tools in Perioperative Stroke Risk Assessment for Asymptomatic Carotid Artery Stenosis with a Focus on the Circle of Willis.

This review aims to explore advancements in perioperative ischemic stroke risk estimation for asymptomatic patients with significant carotid artery stenosis, focusing on Circle of Willis (CoW) morphology based on the CTA or MR diagnostic imaging in the current preoperative diagnostic algorithm. Functional transcranial Doppler (fTCD), near-infrared spectroscopy (NIRS), and optical coherence tomography angiography (OCTA) are discussed in the context of evaluating cerebrovascular reserve capacity and collateral vascular systems, particularly the CoW. These non-invasive diagnostic tools provide additional valuable insights into the cerebral perfusion status. They support biomedical modeling as the gold standard for the prediction of the potential impact of carotid artery stenosis on the hemodynamic changes of cerebral perfusion. Intraoperative risk assessment strategies, including selective shunting, are explored with a focus on CoW variations and their implications for perioperative ischemic stroke and cognitive function decline. By synthesizing these insights, this review underscores the potential of non-invasive diagnostic methods to support clinical decision making and improve asymptomatic patient outcomes by reducing the risk of perioperative ischemic neurological events and preventing further cognitive decline.

Atherosclerotic burden and cerebral small vessel disease: exploring the link through microvascular aging and cerebral microhemorrhages.

Cerebral microhemorrhages (CMHs, also known as cerebral microbleeds) are a critical but frequently underestimated aspect of cerebral small vessel disease (CSVD), bearing substantial clinical consequences. Detectable through sensitive neuroimaging techniques, CMHs reveal an extensive pathological landscape. They are prevalent in the aging population, with multiple CMHs often being observed in a given individual. CMHs are closely associated with accelerated cognitive decline and are increasingly recognized as key contributors to the pathogenesis of vascular cognitive impairment and dementia (VCID) and Alzheimer's disease (AD). This review paper delves into the hypothesis that atherosclerosis, a prevalent age-related large vessel disease, extends its pathological influence into the cerebral microcirculation, thereby contributing to the development and progression of CSVD, with a specific focus on CMHs. We explore the concept of vascular aging as a continuum, bridging macrovascular pathologies like atherosclerosis with microvascular abnormalities characteristic of CSVD. We posit that the same risk factors precipitating accelerated aging in large vessels (i.e., atherogenesis), primarily through oxidative stress and inflammatory pathways, similarly instigate accelerated microvascular aging. Accelerated microvascular aging leads to increased microvascular fragility, which in turn predisposes to the formation of CMHs. The presence of hypertension and amyloid pathology further intensifies this process. We comprehensively overview the current body of evidence supporting this interconnected vascular hypothesis. Our review includes an examination of epidemiological data, which provides insights into the prevalence and impact of CMHs in the context of atherosclerosis and CSVD. Furthermore, we explore the shared mechanisms between large vessel aging, atherogenesis, microvascular aging, and CSVD, particularly focusing on how these intertwined processes contribute to the genesis of CMHs. By highlighting the role of vascular aging in the pathophysiology of CMHs, this review seeks to enhance the understanding of CSVD and its links to systemic vascular disorders. Our aim is to provide insights that could inform future therapeutic approaches and research directions in the realm of neurovascular health.

Presynaptic Rac1 in the hippocampus selectively regulates working memory.

One of the most extensively studied members of the Ras superfamily of small GTPases, Rac1 is an intracellular signal transducer that remodels actin and phosphorylation signaling networks. Previous studies have shown that Rac1-mediated signaling is associated with hippocampal-dependent working memory and longer-term forms of learning and memory and that Rac1 can modulate forms of both pre- and postsynaptic plasticity. How these different cognitive functions and forms of plasticity mediated by Rac1 are linked, however, is unclear. Here, we show that spatial working memory is selectively impaired following the expression of a genetically encoded Rac1-inhibitor at presynaptic terminals, while longer-term cognitive processes are affected by Rac1 inhibition at postsynaptic sites. To investigate the regulatory mechanisms of this presynaptic process, we leveraged new advances in mass spectrometry to identify the proteomic and post-translational landscape of presynaptic Rac1 signaling. We identified serine/threonine kinases and phosphorylated cytoskeletal signaling and synaptic vesicle proteins enriched with active Rac1. The phosphorylated sites in these proteins are at positions likely to have regulatory effects on synaptic vesicles. Consistent with this, we also report changes in the distribution and morphology of synaptic vesicles and in postsynaptic ultrastructure following presynaptic Rac1 inhibition. Overall, this study reveals a previously unrecognized presynaptic role of Rac1 signaling in cognitive processes and provides insights into its potential regulatory mechanisms.

NO Deficiency Compromises Inter- and Intrahemispheric Blood Flow Adaptation to Unilateral Carotid Artery Occlusion.

Carotid artery stenosis (CAS) affects approximately 5-7.5% of older adults and is recognized as a significant risk factor for vascular cognitive impairment (VCI). The impact of CAS on cerebral blood flow (CBF) within the ipsilateral hemisphere relies on the adaptive capabilities of the cerebral microcirculation. In this study, we aimed to test the hypothesis that the impaired availability of nitric oxide (NO) compromises CBF homeostasis after unilateral carotid artery occlusion (CAO). To investigate this, three mouse models exhibiting compromised production of NO were tested: NOS1 knockout, NOS1/3 double knockout, and mice treated with the NO synthesis inhibitor L-NAME. Regional CBF changes following CAO were evaluated using laser-speckle contrast imaging (LSCI). Our findings demonstrated that NOS1 knockout, NOS1/3 double knockout, and L-NAME-treated mice exhibited impaired CBF adaptation to CAO. Furthermore, genetic deficiency of one or two NO synthase isoforms increased the tortuosity of pial collaterals connecting the frontoparietal and temporal regions. In conclusion, our study highlights the significant contribution of NO production to the functional adaptation of cerebrocortical microcirculation to unilateral CAO. We propose that impaired bioavailability of NO contributes to the impaired CBF homeostasis by altering inter- and intrahemispheric blood flow redistribution after unilateral disruption of carotid artery flow.

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.

Morphological and histological investigation of the conduction system in the equine atrial muscle sleeve of pulmonary veins.

BACKGROUND: Atrial fibrillation is the most common arrhythmia in horses causing poor performance. The role of pulmonary vein triggers in the pathogenesis has been identified in horses. Ablation methods have been investigated, but the available information on anatomical, histological and immunohistochemical assessment of the pulmonary vein ostia and the conduction system of the myocardial sleeve is still limited. OBJECTIVES: The aim of the study was to describe the morphological properties of the myocardial sleeve in healthy horses. STUDY DESIGN: Cross-sectional. METHODS: Eighty-three equine hearts were dissected. The number and diameters of pulmonary vein ostia were determined, and anatomical localisation was described. Fifty-eight tissue samples were collected for routine histology and 12 of these were used for immunohistochemistry (connexin 43, 45, S100, and tyrosine hydroxylase antibodies). RESULTS: The mean number of pulmonary vein ostia was 4.5 (4 veins: 46 horse, 5 veins: 31 horses, 6 veins: 6 horses). Diameters (mean ± SD) of the main ostia were as follows: vein I: 20.2 ± 7.0 mm, vein II: 32.7 ± 7.1 mm, vein III: 33.4 ± 5.9 mm, vein IV: 18.1 ± 4.5 mm. Diameters of supernumerary vein ostia varied between 3.0 and 28.0 mm (11.5 ± 5.5 mm). Early branching was found in 26 horses (31.3%) and 30 veins (vein I: 14, vein II: 9, vein III: 5, vein IV: 2). Histology confirmed the presence of a muscle sleeve composed of myocardial tissue in each pulmonary vein. S100 and TH positivity was detected in each vein, and it confirmed the presence of adrenergic and non-adrenergic nerve fibres within the myocardial sleeve. Cx43 and 45 positivity were also found in each vein indicating the presence of gap junctions. MAIN LIMITATIONS: The effect of bodyweight on pulmonary vein dimensions is unknown. CONCLUSIONS: Future ablation techniques should consider that conductive tissue is present in the entire myocardial sleeve in all pulmonary vein ostia.

Impaired cerebrovascular reactivity correlates with reduced retinal vessel density in patients with carotid artery stenosis: Cross-sectional, single center study.

BACKGROUND: The cerebral and retinal circulation systems are developmentally, anatomically, and physiologically interconnected. Thus, we hypothesized that hypoperfusion due to atherosclerotic stenosis of the internal carotid artery (ICA) can result in disturbances of both cerebral and retinal microcirculations. We aimed to characterize parameters indicating cerebrovascular reactivity (CVR) and retinal microvascular density in patients with ICA stenosis, and assess if there is correlation between them. METHODS: In this cross-sectional study the middle cerebral artery (MCA) blood flow velocity was measured by transcranial Doppler (TCD) and, simultaneously, continuous non-invasive arterial blood pressure measurement was performed on the radial artery by applanation tonometry. CVR was assessed based on the response to the common carotid artery compression (CCC) test. The transient hyperemic response ratio (THRR) and cerebral arterial resistance transient hyperemic response ratio (CAR-THRR) were calculated. Optical coherence tomography angiography (OCTA) was used to determine vessel density (VD) on the papilla whole image for all (VDP-WIall) and for small vessels (VDP-WIsmall). The same was done in the peripapillary region: all (VDPPall), and small (VDPPsmall) vessels. The VD of superficial (VDMspf) and deep (VDMdeep) macula was also determined. Significance was accepted when p<0.05. RESULTS: Twenty-four ICA stenotic patients were evaluated. Both CVR and retinal VD were characterized. There was a significant, negative correlation between CAR-THRR (median = -0.40) and VDPPsmall vessels (median = 52%), as well as between VDPPall vessels (median = 58%), and similar correlation between CAR-THRR and VDP-WIsmall (median = 49.5%) and between VDP-WIall (median = 55%). CONCLUSION: The significant correlation between impaired cerebrovascular reactivity and retinal vessel density in patients with ICA stenosis suggests a common mechanism of action. We propose that the combined use of these diagnostic tools (TCD and OCTA) helps to better identify patients with increased ischemic or other cerebrovascular risks.

[Use of allografts in vascular surgery infections]. / Homograftok használata érsebészeti fertozésekben.

With the growing number of patients with vascular endografts, the number of patients with graft infections has also increased. Septic conditions and the choice of grafts are an important challenge in vascular surgery. The aim of this study was to review the literature of the last 7 years showing allograft use in septic conditions in vascular surgery which helps provide insight into the current results of vascular allografts. Data were collected between 1st January 2016 and 31st December 2022. A systematic search was conducted for publications of cryopreserved allograft usage for vascular infection in PubMed and Medline databases. The results of the publications were reviewed based on the following key endpoints: study design, patient's characteristics, mortality rate, graft related complication and reintervention rate, graft patency, limb salvage, graft reinfection rate and survival rate. After a systematic search, 16 publications were included. The articles were divided into two groups: aortic and peripheral. The aortic group included 12 studies covering the data of 542 patients. Early mortality rate (<30 days) was between 2.8% and 42.8%. Allograft-related reintervention rates ranged between 5.9% and 29% (early and late). The rate of graft reinfection was below 10%. 4 studies were included in the peripheral group covering the data of 252 patients. Early mortality rate (<30 days) was between 2.0% and 38%. Allograft-related reintervention rates ranged between 4.0% and 55% (early and late). Reinfection rate was around 4%, but only poor quality data were available. Infections in vascular surgery remain a challenging problem, however, cryopreserved allografts show low reinfection rate and reasonable durability, thus, allografts may be an acceptable option for reconstruction. Orv Hetil. 2023; 164(32): 1256-1262.

Assessment of cerebral autoregulatory function and inter-hemispheric blood flow in older adults with internal carotid artery stenosis using transcranial Doppler sonography-based measurement of transient hyperemic response after carotid artery compression.

Unhealthy vascular aging promotes atherogenesis, which may lead to significant internal carotid artery stenosis (CAS) in 5 to 7.5% of older adults. The pathogenic factors that promote accelerated vascular aging and CAS also affect the downstream portion of the cerebral microcirculation in these patients. Primary treatments of significant CAS are eversion endarterectomy or endarterectomy with patch plasty. Factors that determine adequate hemodynamic compensation and thereby the clinical consequences of CAS as well as medical and surgical complications of carotid reconstruction surgery likely involve the anatomy of the circle of Willis (CoW), the magnitude of compensatory inter-hemispheric blood flow, and the effectiveness of cerebral microcirculatory blood flow autoregulation. This study aimed to test two hypotheses based on this theory. First, we hypothesized that patients with symptomatic and asymptomatic CAS would exhibit differences in autoregulatory function and inter-hemispheric blood flow. Second, we predicted that anatomically compromised CoW would associate with impaired inter-hemispheric blood flow compensation. We enrolled older adults with symptomatic or asymptomatic internal CAS (>70% NASCET criteria; n = 46) and assessed CoW integrity by CT angiography. We evaluated transient hyperemic responses in the middle cerebral arteries (MCA) after common carotid artery compression (CCC; 10 s) by transcranial Doppler sonography (TCD). We compared parameters reflecting autoregulatory function (e.g., transient hyperemic response ratio [THRR], return to baseline time [RTB], changes of vascular resistance) and inter-hemispheric blood flow (residual blood flow velocity). Our findings revealed that CAS was associated with impaired cerebral vascular reactivity. However, we did not observe significant differences in autoregulatory function or inter-hemispheric blood flow between patients with symptomatic and asymptomatic CAS. Moreover, anatomically compromised CoW did not significantly affect these parameters. Notably, we observed an inverse correlation between RTB and THRR, and 49% of CAS patients exhibited a delayed THRR, which associated with decreased inter-hemispheric blood flow. Future studies should investigate how TCD-based evaluation of autoregulatory function and inter-hemispheric blood flow can be used to optimize surgical techniques and patient selection for internal carotid artery revascularization.

The Effect of Circle of Willis Morphology on Retinal Blood Flow in Patients with Carotid Stenosis Measured by Optical Coherence Tomography Angiography.

The Circle of Willis (CoW) is the main collateral system, and its morphological variants are more common in patients who have severe carotid artery stenosis. Earlier data suggest that optical coherence tomography angiography (OCTA) may help to assess the changes in cerebral vascular perfusion by imaging the retinal blood flow. In this single-center prospective clinical study, patients scheduled for carotid endarterectomy (CEA) underwent preoperative computed tomography angiography (CTA) of the extra- and intracranial cerebral circulation. OCTA imaging was performed one week before surgery and postoperatively one month later. The patients were divided into two subgroups based on CTA evaluation of CoW: compromised CoW or non-compromised CoW (containing hypoplastic and normal segments). The effect of the patient's age, OCTA scan quality (SQ), CoW morphology, laterality, and surgery on superficial capillary vessel density (VD) in the macula were assessed in multivariable regression models using linear mixed models. We found that VD significantly decreased with aging (-0.12%; 95%CI: -0.07--0.15; p < 0.001) and was significantly higher in patients with non-compromised CoW morphology (by 0.87% 95%CI (0.26-1.50); p = 0.005). After CEA, retinal blood flow significantly improved by 0.71% (95%CI: 0.18-1.25; p = 0.01). These results suggest that in the case of carotid artery occlusion, patients with non-compromised CoW have more preserved ocular blood flow than subjects with compromised CoW due to remodeling of the intra-orbital blood flow. Measuring the retinal blood flow might be used as a relevant and sensitive indicator of collateral cerebrovascular circulation.