Determinants of prehospital and in-hospital delay in patients with symptomatic carotid stenosis and their influence on the outcome after elective carotid endarterectomy.

BACKGROUND: This study analyses the determinants of prehospital (index event to admission) and in-hospital delay (admission to carotid endarterectomy (CEA)). In addition, the analysis addresses the association between prehospital or in-hospital delay and outcomes after CEA for symptomatic patients in German hospitals. MATERIALS AND METHODS: This retrospective analysis is based on the nationwide German statutory quality assurance database. 55 437 patients were included in the analysis. Prehospital delay was grouped as follows: 180-15, 14-8, 7-3, 2-0 days or 'in-hospital index event'. In-hospital delay was divided into: 0-1, 2-3 and >3 days. The primary outcome event (POE) was in-hospital stroke or death. Univariate and multivariable regression analyses were performed for statistical analysis. The slope of the linear regression line is given as the ß-value, and the rate parameter of the logistic regression is given as the adjusted OR (aOR). RESULTS: Prehospital delay was 0-2 days in 34.9%, 3-14 days in 29.5% and >14 days in 18.6%. Higher age (ß=-1.08, p<0.001) and a more severe index event (transitory ischaemic attack: ß=-4.41, p<0.001; stroke: ß=-6.05, p<0.001, Ref: amaurosis fugax) were determinants of shorter prehospital delay. Higher age (ß=0.28, p<0.001) and female sex (ß=0.09, p=0.014) were associated with a longer in-hospital delay. Index event after admission (aOR 1.23, 95% CI: 1.04 to 1.47) and an intermediate in-hospital delay of 2-3 days (aOR 1.15, 95% CI: 1.00 to 1.33) were associated with an increased POE risk. CONCLUSIONS: This study revealed that older age, higher American Society of Anesthesiology (ASA) stage, increasing severity of symptoms and ipsilateral moderate stenosis were associated with shorter prehospital delay. Non-specific symptoms were associated with a longer prehospital delay. Regarding in-hospital delay, older age, higher ASA stage, contralateral occlusion, preprocedural examination by a neurologist and admission on Fridays or Saturdays were associated with lagged treatment. A very short (<2 days) prehospital and intermediate in-hospital delay (2-3 days) were associated with increased risk of perioperative stroke or death.

Use of an embolic protection device during carotid artery stenting is associated with lower periprocedural risk.

OBJECTIVE: To investigate associations between individual embolic protection device (EPD) use and respective center policy with periprocedural outcomes after carotid artery stenting (CAS). METHODS: This analysis is based on the nationwide German statutory quality assurance database and was funded by Germany's Federal Joint Committee Innovation Fund (G-BA Innovationsfonds, 01VSF19016 ISAR-IQ). According to their policy towards EPD use, hospitals were categorized as routine EPD (>90%), selective EPD (10-90%), or sporadic EPD (<10%) centers. Primary study outcome was in-hospital stroke or death. Univariate and multivariate regression analyses were performed. RESULTS: Overall, 19 302 patients who had undergone CAS between 2013 and 2016 were included. The highest in-hospital stroke or death rate was found in sporadic EPD centers, followed by selective and routine EPD centers (3.1% vs 2.9% vs 1.8%; P<0.001). Across the whole cohort, EPD use was associated with a lower in-hospital stroke or death rate (OR=0.60; 95% CI 0.50 to 0.72). In the multivariate regression analysis, EPD use was independently associated with a lower in-hospital stroke rate (aOR=0.66; 95% CI 0.46 to 0.94). Regarding center policy, routine EPD centers showed a significantly lower in-hospital mortality compared with sporadic EPD centers (aOR=0.44; 95% CI 0.22 to 0.88). CONCLUSIONS: In a contemporary real-world cohort with low risk of selection bias, EPD use was associated with a lower in-hospital risk of stroke. A center policy of routine EPD use was associated with lower mortality. These data support routine use of EPD during CAS to enhance patient safety.

Association between hospital ownership and patient selection, management, and outcomes after carotid endarterectomy or carotid artery stenting : - Secondary data analysis of the Bavarian statutory quality assurance database.

BACKGROUND: This study analyses the association between hospital ownership and patient selection, treatment, and outcome of carotid endarterectomy (CEA) or carotid artery stenting (CAS). METHODS: The analysis is based on the Bavarian subset of the nationwide German statutory quality assurance database. All patients receiving CEA or CAS for carotid artery stenosis between 2014 and 2018 were included. Hospitals were subdivided into four groups: university hospitals, public hospitals, hospitals owned by charitable organizations, and private hospitals. The primary outcome was any stroke or death until discharge from hospital. Research was funded by Germany's Federal Joint Committee Innovation Fund (01VSF19016 ISAR-IQ). RESULTS: In total, 22,446 patients were included. The majority of patients were treated in public hospitals (62%), followed by private hospitals (17%), university hospitals (16%), and hospitals under charitable ownership (6%). Two thirds of patients were male (68%), and the median age was 72 years. CAS was most often applied in university hospitals (25%) and most rarely used in private hospitals (9%). Compared to university hospitals, patients in private hospitals were more likely asymptomatic (65% vs. 49%). In asymptomatic patients, the risk of stroke or death was 1.3% in university hospitals, 1.5% in public hospitals, 1.0% in hospitals of charitable owners, and 1.2% in private hospitals. In symptomatic patients, these figures were 3.0%, 2.5%, 3.4%, and 1.2% respectively. Univariate analysis revealed no statistically significant differences between hospital groups. In the multivariable analysis, compared to university hospitals, the odds ratio of stroke or death in asymptomatic patients treated by CEA was significantly lower in charitable hospitals (OR 0.19 [95%-CI 0.07-0.56, p = 0.002]) and private hospitals (OR 0.47 [95%-CI 0.23-0.98, p = 0.043]). In symptomatic patients (elective treatment, CEA), patients treated in private or public hospitals showed a significantly lower odds ratio compared to university hospitals (0.36 [95%-CI 0.17-0.72, p = 0.004] and 0.65 [95%-CI 0.42-1.00, p = 0.048], respectively). CONCLUSIONS: Hospital ownership was related to patient selection and treatment, but not generally to outcomes. The lower risk of stroke or death in the subgroup of electively treated patients in private hospitals might be due to the right timing, the choice of treatment modality or actually to better structural and process quality.

Macro- and microvascular contributions to cerebral structural alterations in patients with asymptomatic carotid artery stenosis.

Atherosclerosis can underly internal carotid artery stenosis (ICAS), a major risk factor for ischemic stroke, as well as small vessel disease (SVD). This study aimed to investigate hemodynamics and structural alterations associated with SVD in ICAS patients. 28 patients with unilateral asymptomatic ICAS and 30 age-matched controls underwent structural (T1-/T2-weighted and diffusion tensor imaging [DTI]) and hemodynamic (pseudo-continuous arterial spin labeling and dynamic susceptibility contrast) magnetic resonance imaging. SVD-related alterations were assessed using free water (FW), FW-corrected DTI, and peak-width of skeletonized mean diffusivity (PSMD). Furthermore, cortical thickness, cerebral blood flow (CBF), and capillary transit time heterogeneity (CTH) were analyzed. Ipsilateral to the stenosis, cortical thickness was significantly decreased in the posterior dorsal cingulate cortex (p = 0.024) and temporal pole (p = 0.028). ICAS patients exhibited elevated PSMD (p = 0.005), FW (p < 0.001), and contralateral alterations in FW-corrected DTI metrics. We found significantly lateralized CBF (p = 0.011) and a tendency for lateralized CTH (p = 0.067) in the white matter (WM) related to ICAS. Elevated PSMD and FW may indicate a link between SVD and WM changes. Contralateral alterations were seen in FW-corrected DTI, whereas hemodynamic and cortical changes were mainly ipsilateral, suggesting SVD might influence global brain changes concurrent with ICAS-related hemodynamic alterations.

Intraoperative Completion Studies and their Associations with Carotid Endarterectomy Outcomes.

OBJECTIVE: This study aimed at assessing outcomes after carotid endarterectomy (CEA) in dependence of center policy with respect to imaging intraoperative completion study (ICS i ) usage. SUMMARY BACKGROUND DATA: Although randomized controlled studies are missing, a beneficial effect was shown for ICS i techniques (i.e., angiography and intraoperative duplex ultrasound) after CEA. METHODS: This secondary data analysis is based on the German statutory quality assurance database. Research was funded by Germany's Federal Joint Committee Innovation Fund (G-BA Innovationsfonds, 01VSF19016 ISAR-IQ). According to their ICS i policy, hospitals were categorized as routine ICSi (>90%), selective ICSi (10-90%), or sporadic ICSi (<10%) centers . Primary study outcome was in-hospital stroke or death. Multivariable regression analyses were performed. RESULTS: Between 2012 and 2016, a total of 119,800 patients underwent CEA. In-hospital stroke or death rates were lower in routine ICSicenters (1.7%) compared to selective (2.1%) and sporadic ICSicenters (2.0%). The multivariable regression analysis showed, that in routine ICSicenters , ICS i use was associated with lower rates of stroke or death (aOR 0.64; 95% CI 0.44-0.93). In selective ICSicenters , ICS i was not associated with the occurrence of either of the assessed outcomes. In sporadic ICSicenters , ICS i was associated with higher rates of stroke or death (aOR 1.91; 95% CI 1.26-2.91). CONCLUSIONS: Lowest in-hospital stroke or death rates are achieved in r outine ICSicenters . While ICS i is associated with a lower perioperative risk in r outine ICSicenters , it might act as a surrogate marker for worse outcomes due to intraoperative irregularities in sporadic ICSicenters . Routine use of ICS i is advisable.

Spectral computed tomography angiography using a gadolinium-based contrast agent for imaging of pathologies of the aorta.

OBJECTIVES: Especially patients with aortic aneurysms and multiple computed tomography angiographies (CTA) might show medical conditions which oppose the use of iodine-based contrast agents. CTA using monoenergetic reconstructions from dual layer CT and gadolinium (Gd-)based contrast agents might be a feasible alternative in these patients. Therefore, the purpose of this study was to evaluate the feasibility of clinical spectral CTA with a Gd-based contrast agent in patients with aortic aneurysms. METHODS: Twenty-one consecutive scans in 15 patients with and without endovascular aneurysm repair showing contraindications for iodine-based contrast agents were examined using clinical routine doses (0.2 mmol/kg) of Gd-based contrast agent with spectral CT. Monoenergetic reconstructions of the spectral data set were computed. RESULTS: There was a significant increase in the intravascular attenuation of the aorta between pre- and post-contrast images for the MonoE40 images in the thoracic and the abdominal aorta (p < 0.001 for both). Additionally, the ratio between pre- and post-contrast images was significantly higher in the MonoE40 images as compared to the conventional images with a factor of 6.5 ± 4.5 vs. 2.4 ± 0.5 in the thoracic aorta (p = 0.003) and 4.1 ± 1.8 vs. 1.9 ± 0.5 in the abdominal aorta (p < 0.001). CONCLUSIONS: To conclude, our study showed that Gd-CTA is a valid and reliable alternative for diagnostic imaging of the aorta for clinical applications. Monoenergetic reconstructions of computed tomography angiographies using gadolinium based contrast agents may be a useful alternative in patients with aortic aneurysms and contraindications for iodine based contrast agents.

Endovascular aortic repair with sac embolization for the prevention of type II endoleaks (the EVAR-SE study): study protocol for a randomized controlled multicentre study in Germany.

BACKGROUND: Beyond a certain threshold diameter, abdominal aortic aneurysms (AAA) are to be treated by open surgical or endovascular aortic aneurysm repair (EVAR). In a quarter of patients who undergo EVAR, inversion of blood flow in the inferior mesenteric artery or lumbar arteries may lead to type II endoleak (T2EL), which is associated with complications (e.g. AAA growth, secondary type I endoleak, rupture). As secondary interventions to treat T2EL often fail and may be highly invasive, prevention of T2EL is desirable. The present study aims to assess the efficacy of sac embolization (SE) with metal coils during EVAR to prevent T2EL in patients at high risk. METHODS: Over a 24-month recruitment period, a total of 100 patients undergoing EVAR in four vascular centres (i.e. Klinikum rechts der Isar of the Technical University of Munich, University Hospital Augsburg, University Hospital Dresden, St. Joseph's Hospital Wiesbaden) are to be included in the present study. Patients at high risk for T2EL (i.e. ≥ 5 efferent vessels covered by endograft or aneurysmal thrombus volume <40%) are randomized to one group receiving standard EVAR and another group receiving EVAR with SE. Follow-up assessments postoperatively, after 30 days, and 6 months involve contrast-enhanced ultrasound scans (CEUS) and after 12 months an additional computed tomography angiography (CTA) scan. The presence of T2EL detected by CEUS or CTA after 12 months is the primary endpoint. Secondary endpoints comprise quality of life (quantified by the SF-36 questionnaire), reintervention rate, occurrence of type I/III endoleak, aortic rupture, death, alteration of aneurysm volume, or diameter. Standardized evaluation of CTA scans happens through a core lab. The study will be terminated after the final follow-up visit of the ultimate patient. DISCUSSION: Although preexisting studies repeatedly indicated a beneficial effect of SE on T2EL rates after EVAR, patient relevant outcomes have not been assessed until now. The present study is the first randomized controlled multicentre study to assess the impact of SE on quality of life. Further unique features include employment of easily assessable high-risk criteria, a contemporary follow-up protocol, and approval to use any commercially available coil material. Overcoming limitations of previous studies might help SE to be implemented in daily practice and to enhance patient safety. TRIAL REGISTRATION: ClinicalTrials.gov NCT05665101. Registered on 23 December 2022.

Dermal features derived from optoacoustic tomograms via machine learning correlate microangiopathy phenotypes with diabetes stage.

Skin microangiopathy has been associated with diabetes. Here we show that skin-microangiopathy phenotypes in humans can be correlated with diabetes stage via morphophysiological cutaneous features extracted from raster-scan optoacoustic mesoscopy (RSOM) images of skin on the leg. We obtained 199 RSOM images from 115 participants (40 healthy and 75 with diabetes), and used machine learning to segment skin layers and microvasculature to identify clinically explainable features pertaining to different depths and scales of detail that provided the highest predictive power. Features in the dermal layer at the scale of detail of 0.1-1 mm (such as the number of junction-to-junction branches) were highly sensitive to diabetes stage. A 'microangiopathy score' compiling the 32 most-relevant features predicted the presence of diabetes with an area under the receiver operating characteristic curve of 0.84. The analysis of morphophysiological cutaneous features via RSOM may allow for the discovery of diabetes biomarkers in the skin and for the monitoring of diabetes status.

Optoacoustic biomarkers of lipids, hemorrhage and inflammation in carotid atherosclerosis.

Imaging plays a critical role in exploring the pathophysiology and enabling the diagnostics and therapy assessment in carotid artery disease. Ultrasonography, computed tomography, magnetic resonance imaging and nuclear medicine techniques have been used to extract of known characteristics of plaque vulnerability, such as inflammation, intraplaque hemorrhage and high lipid content. Despite the plethora of available techniques, there is still a need for new modalities to better characterize the plaque and provide novel biomarkers that might help to detect the vulnerable plaque early enough and before a stroke occurs. Optoacoustics, by providing a multiscale characterization of the morphology and pathophysiology of the plaque could offer such an option. By visualizing endogenous (e.g., hemoglobin, lipids) and exogenous (e.g., injected dyes) chromophores, optoacoustic technologies have shown great capability in imaging lipids, hemoglobin and inflammation in different applications and settings. Herein, we provide an overview of the main optoacoustic systems and scales of detail that enable imaging of carotid plaques in vitro, in small animals and humans. Finally, we discuss the limitations of this novel set of techniques while investigating their potential to enable a deeper understanding of carotid plaque pathophysiology and possibly improve the diagnostics in future patients with carotid artery disease.

Opening a window to skin biomarkers for diabetes stage with optoacoustic mesoscopy.

Being the largest and most accessible organ of the human body, the skin could offer a window to diabetes-related complications on the microvasculature. However, skin microvasculature is typically assessed by histological analysis, which is not suited for applications to large populations or longitudinal studies. We introduce ultra-wideband raster-scan optoacoustic mesoscopy (RSOM) for precise, non-invasive assessment of diabetes-related changes in the dermal microvasculature and skin micro-anatomy, resolved with unprecedented sensitivity and detail without the need for contrast agents. Providing unique imaging contrast, we explored a possible role for RSOM as an investigational tool in diabetes healthcare and offer the first comprehensive study investigating the relationship between different diabetes complications and microvascular features in vivo. We applied RSOM to scan the pretibial area of 95 participants with diabetes mellitus and 48 age-matched volunteers without diabetes, grouped according to disease complications, and extracted six label-free optoacoustic biomarkers of human skin, including dermal microvasculature density and epidermal parameters, based on a novel image-processing pipeline. We then correlated these biomarkers to disease severity and found statistically significant effects on microvasculature parameters as a function of diabetes complications. We discuss how label-free RSOM biomarkers can lead to a quantitative assessment of the systemic effects of diabetes and its complications, complementing the qualitative assessment allowed by current clinical metrics, possibly leading to a precise scoring system that captures the gradual evolution of the disease.

Patients with Acute Limb Ischemia Might Benefit from Endovascular Therapy-A 17-Year Retrospective Single-Center Series of 985 Patients.

Acute lower limb ischemia (ALI) is a common vascular emergency, requiring urgent revascularization by open or endovascular means. The aim of this retrospective study was to evaluate patient demographics, treatment and periprocedural variables affecting the outcome in ALI patients in a consecutive cohort in a tertiary referral center. Primary outcome events (POE) were 30-day (safety) and 180-day (efficacy) combined mortality and major amputation rates, respectively. Secondary outcomes were perioperative medical and surgical leg-related complications and the 5-year combined mortality and major amputation rate. Statistical analysis used descriptive and uni- and multivariable Cox regression analysis. In 985 patients (71 ± 9 years, 56% men) from 2004 to 2020, the 30-day and 180-day combined mortality and major amputation rates were 15% and 27%. Upon multivariable analysis, older age (30 d: aHR 1.17; 180 d: 1.27) and advanced Rutherford ischemia stage significantly worsened the safety and efficacy POE (30 d: TASC IIa aHR 3.29, TASC IIb aHR 3.93, TASC III aHR 7.79; 180 d: TASC IIa aHR 1.97, TASC IIb aHR 2.43, TASC III aHR 4.2), while endovascular treatment was associated with significant improved POE after 30 days (aHR 0.35) and 180 days (aHR 0.39), respectively. Looking at five consecutive patient quintiles, a significant increase in endovascular procedures especially in the last quintile could be observed (17.5% to 39.5%, p < 0.001). Simultaneously, the re-occlusion rate as well as the number of patients with any previous revascularization increased. In conclusion, despite a slightly increasing early re-occlusion rate, endovascular treatment might, if possible, be favorable in ALI treatment.

Stronger influence of systemic than local hemodynamic-vascular factors on resting-state BOLD functional connectivity.

Correlated fluctuations in the blood oxygenation level dependent (BOLD) signal of resting-state functional MRI (i.e., BOLD-functional connectivity, BOLD-FC) reflect a spectrum of neuronal and non-neuronal processes. In particular, there are multiple hemodynamic-vascular influences on BOLD-FC on both systemic (e.g., perfusion delay) and local levels (e.g., neurovascular coupling). While the influence of individual factors has been studied extensively, combined and comparative studies of systemic and local hemodynamic-vascular factors on BOLD-FC are scarce, notably in humans. We employed a multi-modal MRI approach to investigate and compare distinct hemodynamic-vascular processes and their impact on homotopic BOLD-FC in healthy controls and patients with unilateral asymptomatic internal carotid artery stenosis (ICAS). Asymptomatic ICAS is a cerebrovascular disorder, in which neuronal functioning is largely preserved but hemodynamic-vascular processes are impaired, mostly on the side of stenosis. Investigated indicators for local hemodynamic-vascular processes comprise capillary transit time heterogeneity (CTH) and cerebral blood volume (CBV) from dynamic susceptibility contrast (DSC) MRI, and cerebral blood flow (CBF) from pseudo-continuous arterial spin labeling (pCASL). Indicators for systemic processes are time-to-peak (TTP) from DSC MRI and BOLD lags from functional MRI. For each of these parameters, their influence on BOLD-FC was estimated by a comprehensive linear mixed model. Equally across groups, we found that individual mean BOLD-FC, local (CTH, CBV, and CBF) and systemic (TTP and BOLD lag) hemodynamic-vascular factors together explain 40.7% of BOLD-FC variance, with 20% of BOLD-FC variance explained by hemodynamic-vascular factors, with an about two-times larger contribution of systemic versus local factors. We conclude that regional differences in blood supply, i.e., systemic perfusion delays, exert a stronger influence on BOLD-FC than impairments in local neurovascular coupling.

Clinical and Translational Imaging and Sensing of Diabetic Microangiopathy: A Narrative Review.

Microvascular changes in diabetes affect the function of several critical organs, such as the kidneys, heart, brain, eye, and skin, among others. The possibility of detecting such changes early enough in order to take appropriate actions renders the development of appropriate tools and techniques an imperative need. To this end, several sensing and imaging techniques have been developed or employed in the assessment of microangiopathy in patients with diabetes. Herein, we present such techniques; we provide insights into their principles of operation while discussing the characteristics that make them appropriate for such use. Finally, apart from already established techniques, we present novel ones with great translational potential, such as optoacoustic technologies, which are expected to enter clinical practice in the foreseeable future.

Bony Stroke: Ischemic Stroke Caused by Mechanical Stress on Brain Supplying Arteries From Anatomical Bone or Cartilage Anomalies.

BACKGROUND: Bone or cartilage anomalies with affection of brain supplying arteries are a potential structural cause for ischemic stroke. In the following, we termed this entity bony stroke. Due to rarity of their description, there is no standardized workup and therapy for bony strokes. METHODS: Retrospectively, we extracted diagnostic and therapeutic workup of all patients considered to have had a bony stroke between January 2017 to March 2022 at our comprehensive care center. RESULTS: In total, 6 patients classified as a bony stroke were identified among 4200 acute patients with ischemic stroke treated during the study period. Each patient had recurrent ischemic strokes in the dependent vascular territory before diagnosis. Diagnosis was achieved by a combination of imaging devices, including sonography, computed tomography, and magnetic resonance imaging. In addition to conventional static imaging, the application of dynamic imaging modalities with the patients' head in rotation or reclination confirmed a vessel affection following head movements in 3 patients (50%). Treatment options were interdisciplinary assessed and included the following: conservative treatment (n=1), endovascular stenting (n=2) or occlusion (n=2), surgical removal of bone/ cartilage (n=2), and surgical bypass treatment (n=1). In follow-up (mean 11.7 months), no patient experienced further ischemia. CONCLUSIONS: As a differential diagnosis, bony strokes may be considered in patients with recurrent ischemic stroke of unknown cause in one dependent vascular territory. Interdisciplinary evaluation and treatment may eliminate risk of stroke recurrence.

Skeletal muscle optoacoustics reveals patterns of circulatory function and oxygen metabolism during exercise.

Imaging skeletal muscle function and metabolism, as reported by local hemodynamics and oxygen kinetics, can elucidate muscle performance, severity of an underlying disease or outcome of a treatment. Herein, we used multispectral optoacoustic tomography (MSOT) to image hemodynamics and oxygen kinetics within muscle during exercise. Four healthy volunteers underwent three different hand-grip exercise challenges (60s isometric, 120s intermittent isometric and 60s isotonic). During isometric contraction, MSOT showed a decrease of HbO2, Hb and total blood volume (TBV), followed by a prominent increase after the end of contraction. Corresponding hemodynamic behaviors were recorded during the intermittent isometric and isotonic exercises. A more detailed analysis of MSOT readouts revealed insights into arteriovenous oxygen differences and muscle oxygen consumption during all exercise schemes. These results demonstrate an excellent capability of visualizing both circulatory function and oxygen metabolism within skeletal muscle under exercise, with great potential implications for muscle research, including relevant disease diagnostics.

Non-invasive multispectral optoacoustic tomography resolves intrahepatic lipids in patients with hepatic steatosis.

Hepatic steatosis is characterized by intrahepatic lipid accumulation and may lead to irreversible liver damage if untreated. Here, we investigate whether multispectral optoacoustic tomography (MSOT) can offer label-free detection of liver lipid content to enable non-invasive characterization of hepatic steatosis by analyzing the spectral region around 930 nm, where lipids characteristically absorb. In a pilot study, we apply MSOT to measure liver and surrounding tissues in five patients with liver steatosis and five healthy volunteers, revealing significantly higher absorptions at 930 nm in the patients, while no significant difference was observed in the subcutaneous adipose tissue of the two groups. We further corroborated the human observations with corresponding MSOT measurements in high fat diet (HFD) - and regular chow diet (CD)-fed mice. This study introduces MSOT as a potential non-invasive and portable technique for detecting/monitoring hepatic steatosis in clinical settings, providing justification for larger studies.

External Validity of Randomised Controlled Trials on Carotid Revascularisation: Trial Populations May Not Always Reflect Patients in Clinical Practice.

OBJECTIVE: The external validity of randomised controlled trials (RCTs) and their transferability to clinical practice is under investigated. This study aimed to analyse the exclusion criteria of recent carotid RCTs comparing carotid endarterectomy (CEA) and carotid artery stenting, and to assess the eligibility of consecutive clinical practice cohorts to those RCTs. METHODS: An analysis of the clinical and anatomical exclusion criteria of RCTs for asymptomatic (SPACE-2, ACST-2, CREST-1, and CREST-2) and symptomatic carotid stenosis (SPACE-1, CREST-1, ICSS, and EVA-3S) was performed. Two hundred consecutive asymptomatic and 200 consecutive symptomatic patients, treated by CEA, or transfemoral or transcarotid artery stenting at a tertiary referral university centre were assessed for their potential eligibility for each corresponding RCT. RCT patient data were pooled and differences from the clinical practice cohort analysed. Statistics were descriptive and comparative using Fisher's exact and t tests. RESULTS: The number of clinical and anatomical exclusion criteria differed widely between RCTs. Potential eligibility rates of the clinical practice cohort for RCTs with regard to asymptomatic carotid stenosis were 80.5% (ACST-2), 79.5% (SPACE-2), 47% (CREST-1), and 20% (CREST-2). For RCTs on symptomatic carotid stenosis the eligibility rates were 89% (ICSS), 86.5% (EVA-3S), 64% (SPACE-1), and 39% (CREST-1). Both clinical practice cohorts were older by about three years and patients were more often male vs. the RCTs. Furthermore, a history of smoking (asymptomatic patients), hypertension (symptomatic patients), and atrial fibrillation was diagnosed more often, whereas hypercholesterolaemia and coronary heart disease (asymptomatic patients) were less prevalent. More clinical practice patients were on antiplatelets, anticoagulants, and lipid lowering drugs. Symptomatic clinical practice patients presented more often with retinal ischaemia and less often with minor hemispheric strokes than patients in the RCTs. CONCLUSION: The external validity of contemporary carotid RCTs varies considerably. Patients in routine clinical practice differ from RCT populations with respect to age, comorbidities, and medication. These data are of interest for clinicians and guideline authors and may be relevant for the design of future comparative trials.

Resting-state BOLD functional connectivity depends on the heterogeneity of capillary transit times in the human brain A combined lesion and simulation study about the influence of blood flow response timing.

Functional connectivity (FC) derived from blood oxygenation level dependent (BOLD) functional magnetic resonance imaging at rest (rs-fMRI), is commonly interpreted as indicator of neuronal connectivity. In a number of brain disorders, however, metabolic, vascular, and hemodynamic impairments can be expected to alter BOLD-FC independently from neuronal activity. By means of a neurovascular coupling (NVC) model of BOLD-FC, we recently demonstrated that aberrant timing of cerebral blood flow (CBF) responses may influence BOLD-FC. In the current work, we support and extend this finding by empirically linking BOLD-FC with capillary transit time heterogeneity (CTH), which we consider as an indicator of delayed and broadened CBF responses. We assessed 28 asymptomatic patients with unilateral high-grade internal carotid artery stenosis (ICAS) as a hemodynamic lesion model with largely preserved neurocognitive functioning and 27 age-matched healthy controls. For each participant, we obtained rs-fMRI, arterial spin labeling, and dynamic susceptibility contrast MRI to study the dependence of left-right homotopic BOLD-FC on local perfusion parameters. Additionally, we investigated the dependency of BOLD-FC on CBF response timing by detailed simulations. Homotopic BOLD-FC was negatively associated with increasing CTH differences between homotopic brain areas. This relation was more pronounced in asymptomatic ICAS patients even after controlling for baseline CBF and relative cerebral blood volume influences. These findings match simulation results that predict an influence of delayed and broadened CBF responses on BOLD-FC. Results demonstrate that increasing CTH differences between homotopic brain areas lead to BOLD-FC reductions. Simulations suggest that CTH increases correspond to broadened and delayed CBF responses to fluctuations in ongoing neuronal activity.

[Important recommendations of the German-Austrian S3 guidelines on management of extracranial carotid artery stenosis]. / Wichtige Empfehlungen der deutsch-österreichischen S3-Leitlinie zum Management extrakranieller Karotisstenosen.

BACKGROUND: Lesions of the extracranial carotid artery are the cause of 10-15 % of all cases of cerebral ischemia. The aims of the updated S3 guidelines are evidence-based and consensus-based recommendations for action on comprehensive care of patients with extracranial carotid stenosis in Germany and Austria. METHODS: A systematic literature search (1990-2019) and methodical assessment of existing guidelines and systematic reviews were carried out. Consensus answers to 37 key questions with evidence-based recommendations. RESULTS: The prevalence of extracranial carotid stenosis is approximately 4% and increases after the age of 65 years. The most important examination method is duplex sonography. Randomized controlled studies (RCT) have shown that carotid endarterectomy (CEA) of an asymptomatic 60-99% carotid artery stenosis reduces the absolute risk of stroke (absolute risk reduction, ARR) within 5 years in comparison to drug treatment alone by 4.1%. Due to an improved pharmaceutical prevention of arteriosclerosis, the S3 guidelines recommend a prophylactic CEA of a 60-99% stenosis only for patients without an increased surgical risk. Additionally, one or more clinical or imaging results should be present, which indicate an increased risk of carotid-related stroke in the follow-up. For medium-grade (50-69 %) and high-grade (70-99 %) symptomatic stenoses the ARRs after 5 years are 4.6% and 15.6%, respectively. Systematic reviews of RCTs have shown that CEA is associated with a ca. 50% lower periprocedural risk of stroke compared to carotid artery stenting (CAS). There are no differences in the long-term course. The CEA is recommended for high-grade asymptomatic, medium-grade and high-grade symptomatic carotid stenosis as a standard procedure, alternatively CAS can be considered. For both procedures the periprocedural stroke rate/mortality during hospitalization should be a maximum of 2% (asymptomatic stenosis) or 4% (symptomatic stenosis). CONCLUSION: Both CEA and CAS necessitate a critical evaluation of the indications and strict quality criteria. Future studies should evaluate even better selection criteria for an individual, optimal, conservative, operative or endovascular treatment.

Hemodynamic MRI parameters to predict asymptomatic unilateral carotid artery stenosis with random forest machine learning.

Background: Internal carotid artery stenosis (ICAS) can cause stroke and cognitive decline. Associated hemodynamic impairments, which are most pronounced within individual watershed areas (iWSA) between vascular territories, can be assessed with hemodynamic-oxygenation-sensitive MRI and may help to detect severely affected patients. We aimed to identify the most sensitive parameters and volumes of interest (VOI) to predict high-grade ICAS with random forest machine learning. We hypothesized an increased predictive ability considering iWSAs and a decreased cognitive performance in correctly classified patients. Materials and methods: Twenty-four patients with asymptomatic, unilateral, high-grade carotid artery stenosis and 24 age-matched healthy controls underwent MRI comprising pseudo-continuous arterial spin labeling (pCASL), breath-holding functional MRI (BH-fMRI), dynamic susceptibility contrast (DSC), T2 and T2* mapping, MPRAGE and FLAIR. Quantitative maps of eight perfusion, oxygenation and microvascular parameters were obtained. Mean values of respective parameters within and outside of iWSAs split into gray (GM) and white matter (WM) were calculated for both hemispheres and for interhemispheric differences resulting in 96 features. Random forest classifiers were trained on whole GM/WM VOIs, VOIs considering iWSAs and with additional feature selection, respectively. Results: The most sensitive features in decreasing order were time-to-peak (TTP), cerebral blood flow (CBF) and cerebral vascular reactivity (CVR), all of these inside of iWSAs. Applying iWSAs combined with feature selection yielded significantly higher receiver operating characteristics areas under the curve (AUC) than whole GM/WM VOIs (AUC: 0.84 vs. 0.90, p = 0.039). Correctly predicted patients presented with worse cognitive performances than frequently misclassified patients (Trail-making-test B: 152.5s vs. 94.4s, p = 0.034). Conclusion: Random forest classifiers trained on multiparametric MRI data allow identification of the most relevant parameters and VOIs to predict ICAS, which may improve personalized treatments.