Internal Carotid Artery Blood Flow Research Articles

Dynamic cerebral autoregulation is preserved during orthostasis and intrathoracic pressure regulation in healthy subjects: A pilot study.

Resistance breathing may restore cardiac output (CO) and cerebral blood flow (CBF) during hypovolemia. We assessed CBF and cerebral autoregulation (CA) during tilt, resistance breathing, and paced breathing in 10 healthy subjects. Blood velocities in the internal carotid artery (ICA), middle cerebral arteries (MCA, four subjects), and aorta were measured by Doppler ultrasound in 30° and 60° semi-recumbent positions. ICA blood flow and CO were calculated. Arterial blood pressure (ABP, Finometer), and end-tidal CO2 (ETCO2) were recorded. ICA blood flow response was assessed by mixed-models regression analysis. The synchronization index (SI) for the variable pairs ABP-ICA blood velocity, ABP-MCA velocities in 0.005-0.08 Hz frequency interval was calculated as a measure of CA. Passive tilting from 30° to 60° resulted in 12% decrease in CO (p = 0.001); ICA blood flow tended to fall (p = 0.04); Resistance breathing restored CO and ICA blood flow despite a 10% ETCO2 drop. ETCO2 and CO contributed to ICA blood flow variance (adjusted R2: 0.9, p < 0.0001). The median SI was low (<0.2) indicating intact CA, confirmed by surrogate date testing. The peak SI was transiently elevated during resistance breathing in the 60° position. Resistance breathing may transiently reduce CA efficiency. Paced breathing did not restore CO or ICA blood flow.

Reduced fetal cerebral blood flow predicts perinatal mortality in a mouse model of prenatal alcohol and cannabinoid exposure

BackgroundChildren exposed prenatally to alcohol or cannabinoids individually can exhibit growth deficits and increased risk for adverse birth outcomes. However, these drugs are often co-consumed and their combined effects on early brain development are virtually unknown. The blood vessels of the fetal brain emerge and mature during the neurogenic period to support nutritional needs of the rapidly growing brain, and teratogenic exposure during this gestational window may therefore impair fetal cerebrovascular development.Study DesignTo determine whether prenatal polysubstance exposure confers additional risk for impaired fetal-directed blood flow, we performed high resolution in vivo ultrasound imaging in C57Bl/6J pregnant mice. After pregnancy confirmation, dams were randomly assigned to one of four groups: drug-free control, alcohol-exposed, cannabinoid-exposed or alcohol-and-cannabinoid-exposed. Drug exposure occurred daily between Gestational Days 12–15, equivalent to the transition between the first and second trimesters in humans. Dams first received an intraperitoneal injection of either cannabinoid agonist CP-55,940 (750 µg/kg) or volume-equivalent vehicle. Then, dams were placed in vapor chambers for 30 min of inhalation of either ethanol or room air. Dams underwent ultrasound imaging on three days of pregnancy: Gestational Day 11 (pre-exposure), Gestational Day 13.5 (peri-exposure) and Gestational Day 16 (post-exposure).ResultsAll drug exposures decreased fetal cranial blood flow 24-hours after the final exposure episode, though combined alcohol and cannabinoid co-exposure reduced internal carotid artery blood flow relative to all other exposures. Umbilical artery metrics were not affected by drug exposure, indicating a specific vulnerability of fetal cranial circulation. Cannabinoid exposure significantly reduced cerebroplacental ratios, mirroring prior findings in cannabis-exposed human fetuses. Post-exposure cerebroplacental ratios significantly predicted subsequent perinatal mortality (p = 0.019, area under the curve, 0.772; sensitivity, 81%; specificity, 85.70%) and retroactively diagnosed prior drug exposure (p = 0.005; AUC, 0.861; sensitivity, 86.40%; specificity, 66.7%).ConclusionsFetal cerebrovasculature is significantly impaired by exposure to alcohol or cannabinoids, and co-exposure confers additional risk for adverse birth outcomes. Considering the rising potency and global availability of cannabis products, there is an imperative for research to explore translational models of prenatal drug exposure, including polysubstance models, to inform appropriate strategies for treatment and care in pregnancies affected by drug exposure.

Hemorrhage at high altitude: impact of sustained hypobaric hypoxia on cerebral blood flow, tissue oxygenation, and tolerance to simulated hemorrhage in humans.

With ascent to high altitude (HA), compensatory increases in cerebral blood flow and oxygen delivery must occur to preserve cerebral metabolism and consciousness. We hypothesized that this compensation in cerebral blood flow and oxygen delivery preserves tolerance to simulated hemorrhage (via lower body negative pressure, LBNP), such that tolerance is similar during sustained exposure to HA vs. low altitude (LA). Healthy humans (4F/4M) participated in LBNP protocols to presyncope at LA (1130m) and 5-7days following ascent to HA (3800m). Internal carotid artery (ICA) blood flow, cerebral delivery of oxygen (CDO2) through the ICA, and cerebral tissue oxygen saturation (ScO2) were determined. LBNP tolerance was similar between conditions (LA: 1276 ± 304s vs. HA: 1208 ± 306s; P = 0.58). Overall, ICA blood flow and CDO2 were elevated at HA vs. LA (P ≤ 0.01) and decreased with LBNP under both conditions (P < 0.0001), but there was no effect of altitude on ScO2 responses (P = 0.59). Thus, sustained exposure to hypobaric hypoxia did not negatively impact tolerance to simulated hemorrhage. These data demonstrate the robustness of compensatory physiological mechanisms that preserve human cerebral blood flow and oxygen delivery during sustained hypoxia, ensuring cerebral tissue metabolism and neuronal function is maintained.

Cerebral Blood Flow Patterns in Patients With Low-Flow Carotid Artery Stenosis, a 4D-PCMRI Assessment.

Compromised cerebral blood flow can contribute to future ischemic events in patients with symptomatic carotid artery disease. However, there is limited knowledge of the effects on cerebral hemodynamics resulting from a reduced internal carotid artery (ICA) blood flow rate (BFR). Investigate how reduced ICA-BFR, relates to BFR in the cerebral arteries. Prospective. Thirty-eight patients, age 72 ± 6 years (11 female). 3-Tesla, four-dimensional phase-contrast magnetic resonance imaging (4D-PCMRI). Patients with ischemic stroke or transient ischemic attack were evaluated regarding the degree of stenosis. 4D-PCMRI was used to measure cerebral BFR in 38 patients with symptomatic carotid stenosis (≥50%). BFR in the cerebral arteries was assessed in two subgroups based on symptomatic ICA-BFR: reduced ICA-flow (<160 mL/minutes) and preserved ICA-flow (≥160 mL/minutes). BFR laterality was defined as a difference in the paired ipsilateral-contralateral arteries. Patients were grouped based on ICA-BFR (reduced vs. preserved). Statistical tests (independent sample t-test/paired t-test) were used to compare groups and hemispheres. Significance was determined at P < 0.05. The degree of stenosis was not significantly different, 80% (95% confidence interval [CI] = 73%-87%) in the reduced ICA-flow vs. 72% (CI = 66%-76%) in the preserved ICA-flow; P = 0.09. In the reduced ICA-flow group, a significantly reduced BFR was found in the ipsilateral middle cerebral artery and anterior cerebral artery (A1), while significantly increased in the contralateral A1. Retrograde BFR was found in the posterior communicating artery and ophthalmic artery. Significant BFR laterality was present in all paired arteries in the reduced ICA-flow group, contrasting the preserved ICA-flow group (P = 0.14-0.93). 4D-PCMRI revealed compromised cerebral BFR due to carotid stenosis, not possible to detect by solely analyzing the degree of stenosis. In patients with reduced ICA-flow, collaterals were not sufficient to maintain symmetrical BFR distribution to the two hemispheres. 2 TECHNICAL EFFICACY: Stage 3.

Transcranial Doppler in Childhood Moyamoya: An Underutilized Tool?

BackgroundChildren with moyamoya are at high risk for incident and recurrent stroke. Transcranial Doppler (TCD) ultrasound is an attractive option to screen high-risk populations for moyamoya and to provide stroke risk stratification information due to its safety and cost-effectiveness. We used TCD to evaluate cerebral blood flow velocities in children with presurgical moyamoya and to determine if velocities differ between children with stable and unstable disease. MethodsFourteen participants aged ≤21 years with a radiographic diagnosis of moyamoya or moyamoya-like arteriopathy underwent a research TCD at a median age of 7.2 years. TCDs were performed outside of the setting of acute stroke and before surgical revascularization. Arteriopathy was classified as unstable if the participant had a stroke or transient ischemic attack within three months preceding the TCD. ResultsMiddle cerebral artery and internal carotid artery (ICA) blood flow velocities were elevated. The median M1 velocity was 138 cm/s (interquartile range [IQR] 106 to 168). Individual M1 flow velocities were a median of 5.0 S.D.s above age-based normative values. The median distal ICA velocity was 146 cm/s (IQR 124 to 163). Individual ICA flow velocities were a median of 5.9 S.D.s above normative values. Participants with unstable arteriopathy had higher M1 velocities compared with those with stable arteriopathy (170 vs 119 cm/s, P = 0.0003). We did not identify velocity differences based on comorbid conditions or age. ConclusionsThese preliminary data suggest that TCD is a promising tool for screening for cerebral arteriopathies in high-risk pediatric populations and assessment for unstable disease.

Radiological features of internal carotid artery occlusion caused by pituitary apoplexy: illustrative case.

Pituitary apoplexy rarely causes internal carotid artery (ICA) occlusion and acute ischemic stroke. Some cases have been reported, but the neuroimaging findings, including cerebral angiography, have not been discussed. A 55-year-old male suffered the sudden onset of right cervical pain and left mild hemiparesis. Computed tomography indicated a pituitary mass, and magnetic resonance angiography showed a right ICA occlusion. The initial diagnosis was ICA occlusion caused by ICA dissection. His symptoms worsened and the region of cerebral infarction expanded, so the patient was transferred to our hospital. Magnetic resonance imaging and cerebral angiography showed the sudden stoppage of right ICA blood flow caused by local compression of the tumor near the distal dural ring. The diagnosis was acute ischemic stroke resulting from ICA pseudo-occlusion caused by pituitary apoplexy, and emergent endoscopic transsphenoidal resection was performed. Postoperatively, the right ICA was completely patent, and hemiparesis was improved with rehabilitation. ICA occlusion caused by pituitary apoplexy is very rare, but emergent treatment is necessary. However, the pathology is difficult to diagnose quickly. Neuroimaging findings showing that the ICA is easily stenosed or occluded if rapidly compressed by the tumor near the distal dural ring may be useful to rapidly diagnose and treat.

The Prevalence and Impact of Vertebral Artery Hypoplasia on Cerebral Hemodynamics

AbstractBackgroundVertebral artery hypoplasia (VAH) is an anatomical variation that may be associated with lower cerebral blood flow. We demonstrated the prevalence of VAH to be approximately 26% in a pilot study of healthy adults (n = 39). The purpose of this study was to expand on these findings by determining the prevalence of VAH and its impact on cerebral hemodynamics in a larger sample size of middle‐aged and older adults.MethodA total of 550 participants (66 ± 9 years; 346 females) underwent 4D flow MRI scans to evaluate the internal carotid arteries (ICA), vertebral arteries, and basilar artery. VAH+ (positive for VAH) was determined from the 4D flow MRI scans using both diameter (&lt;2.5 mm) and flow (&lt;47 mL/min).ResultWe identified 152 participants as VAH+ (prevalence of 28%). The prevalence of VAH+ was similar between females (n = 95; 27%) and males (n = 57; 28%). VAH predominantly occurred in the right vertebral artery (n = 102; 67%). As expected within VAH+ participants, the hypoplastic vertebral artery diameter was smaller (2.0±0.2 mm vs. 2.8±0.5 mm; p&lt;0.001), blood flow was lower (29±10 ml/min vs. 100±44 ml/min; p&lt;0.001), and pulsatility index was higher (1.8±0.6 a.u. vs. 1.3±0.3 a.u.; p&lt;0.001) compared to the contralateral artery. There were no differences in ICA diameter (p = 0.875), blood flow (p = 0.553) or pulsatility index (p = 0.984) between VAH+ and no VAH. When evaluating the basilar artery, the diameter was smaller (2.7±0.4 mm vs. 2.8±0.4 mm; p = 0.037) with lower blood flow (105±35 ml/min vs. 116±37 ml/min; p&lt;0.001) in VAH+ compared with no VAH. Males with VAH+ had higher basilar artery pulsatility index compared with males with no VAH (1.4±0.4 a.u. vs. 1.2±0.3 a.u.; p = 0.004), but this was not apparent in females (p = 0.544). When comparing global cerebral blood flow, there was a trend for lower flow in VAH+ compared with no VAH (p = 0.096).ConclusionWe demonstrated VAH prevalence to be around 28%, with similar prevalence in both males and females. VAH was associated with impaired regional flow and with elevated basilar artery cerebral pulsatility in males.

Cerebral hemodynamic effects of head-up CPR in a porcine model

AimTo assess the hemodynamic effects of head elevation on cerebral perfusion during cardiopulmonary resuscitation (CPR) in a porcine model of cardiac arrest. MethodsVF was induced in eight 65 kg pigs that were treated with CPR after five minutes of no flow. Mean arterial pressure (MAP) was measured at the descending thoracic aorta. Internal carotid artery blood flow (CBF) was measured with an ultrasound probe. Cerebral perfusion pressure (CerPP) was calculated in two ways (CerPPICAP and CerPPreported) using the same intracranial pressure (ICP) measurement. CePPreported was calculated as MAP-ICP. CerPPICAP was calculated by using intracranial arterial pressure (ICAP) – ICP. The animals were switched between head up (HUP) and supine (SUP) CPR every five minutes for a total of twenty minutes of resuscitation. ResultsMAP and coronary perfusion pressure measurements were similar in both CPR positions (p = 0.36 and p = 0.1, respectively). ICP was significantly lower in the HUP CPR group (14.7 ± 1 mm Hg vs 26.9 ± 1 mm Hg, p < 0.001) as was ICAP (30.1 ± 2 mm Hg vs 42.6 ± 1 mmHg, p < 0.001). The proportional decrease in ICP and ICAP resulted in similar CerPPICAP comparing HUP and SUPCPR (p = 0.7). CBF was significantly lower during HUPCPR when compared to SUPCPR (58.5 ± 3 ml/min vs 78 ± 4 ml/min, p < 0.001). A higher CerPPreported was found during the HUP compared to SUP-CPR, when MAP was used (36.6 ± 2 mm Hg vs 23 ± 2 mm Hg, p < 0.001) without correcting for the hydrostatic pressure drop. ConclusionHUP did not affect cerebral perfusion pressure and it significantly decreased internal carotid blood flow.

The effect of oscillatory hemodynamics on the cardiovascular responses to simulated hemorrhage during isocapnia.

During cerebral hypoperfusion induced by lower body negative pressure (LBNP), cerebral tissue oxygenation is protected with oscillatory arterial pressure and cerebral blood flow at low frequencies (0.1 Hz and 0.05 Hz), despite no protection of cerebral blood flow or oxygen delivery. However, hypocapnia induced by LBNP contributes to cerebral blood flow reductions, and may mask potential protective effects of hemodynamic oscillations on cerebral blood flow. We hypothesized that under isocapnic conditions, forced oscillations of arterial pressure and blood flow at 0.1 Hz and 0.05 Hz would attenuate reductions in extra- and intracranial blood flow during simulated hemorrhage using LBNP. Eleven human participants underwent three LBNP profiles: a nonoscillatory condition (0 Hz) and two oscillatory conditions (0.1 Hz and 0.05 Hz). End-tidal (et) CO2 and etO2 were clamped at baseline values using dynamic end-tidal forcing. Cerebral tissue oxygenation (ScO2), internal carotid artery (ICA) blood flow, and middle cerebral artery velocity (MCAv) were measured. With clamped etCO2, neither ICA blood flow (ANOVA P = 0.93) nor MCAv (ANOVA P = 0.36) decreased with LBNP, and these responses did not differ between the three profiles (ICA blood flow: 0 Hz: 2.2 ± 5.4%, 0.1 Hz: -0.4 ± 6.6%, 0.05 Hz: 0.2 ± 4.8%; P = 0.56; MCAv: 0 Hz: -2.3 ± 7.8%, 0.1 Hz: -1.3 ± 6.1%, 0.05 Hz: -3.1 ± 5.0%; P = 0.87). Similarly, ScO2 did not decrease with LBNP (ANOVA P = 0.21) nor differ between the three profiles (0 Hz: -2.6 ± 3.3%, 0.1 Hz: -1.6 ± 1.5%, 0.05 Hz: -0.2 ± 2.8%; P = 0.13). Contrary to our hypothesis, cerebral blood flow and tissue oxygenation were protected during LBNP with isocapnia, regardless of whether hemodynamic oscillations were induced.NEW & NOTEWORTHY We examined the role of forcing oscillations in arterial pressure and blood flow at 0.1 Hz and 0.05 Hz on extra- and intracranial blood flow and cerebral tissue oxygenation during simulated hemorrhage (using lower body negative pressure, LBNP) under isocapnic conditions. Contrary to our hypothesis, both cerebral blood flow and cerebral tissue oxygenation were completely protected during simulated hemorrhage with isocapnia, regardless of whether oscillations in arterial pressure and cerebral blood flow were induced. These findings highlight the protective effect of preventing hypocapnia on cerebral blood flow under simulated hemorrhage conditions.

Imaging methods in assessing the surveillance of type 2 diabetes mellitus for cerebrovascular reserve and brain disease in patients with hemodynamically significant carotid stenosis

Introduction. Type 2 diabetes is the most common form of endocrine disease. Diabetes is a well-established risk factor for stroke. Carotid endarterectomy (CEE) is the main method of preventing a serious complication of stroke in patients with carotid stenosis. Consequently, the assess of type 2 diabetes on the results of CEE is an urgent problem of angiosurgery.Aim: To assess effect of type 2 diabetes on cerebrovascular reserve capacity and brain structure in patients with carotid atherosclerosis by ultrasound and magnetic resonance diagnostic.Material and Methods. 44 patients with hemodynamically significant stenosis of the internal carotid arteries (ICA), who underwent ultrasound and magnetic resonance examinations of the carotid arteries at the pre- and postoperative stages were included in this study. Two groups were formed: group I (n =15) – with a verified diagnosis of type 2 diabetes, group II (n = 29) – without diabetes. To assess the cerebrovascular reserve, functional hypercapnic and hyperoxic tests were performed.Results. The analysis of the results showed statistically significant differences in the ICA blood flow in both groups. Intergroup comparison before surgery in the middle cerebral artery on the side of hemodynamically significant stenosis revealed a statistically significant difference in pulsation and peripheral resistance index. In the common carotid arteries on both sides, significant intergroup differences were found in the velocity parameters of blood flow after the CEE operation. The reactivity index in patients with surgical stenosis with type 2 diabetes in the hyperoxic test was statistically significantly different on the side of the stenosis compared to the same indicator in the group without diabetes. There were no statistically significant differences in the hypercapnic test. The value of reactivity index indicates a negative or paradoxical reaction.Conclusion. The use of simple and accessible functional tests to assess cerebrovascular reserve, plaque structure and changes in the brain in patients with type 2 diabetes at the stage of preoperative preparation according to ultrasound and MRI studies allows us to correct the treatment and subsequent protection of the brain at the stage of surgery to prevent possible complications.

Internal Carotid Artery Blood Flow Response to Anaesthesia, Pneumoperitoneum and Head-Up Tilt During Laparoscopic Cholecystectomy: A Clinical Study

Background: Control of cerebral blood flow (CBF) is complex and is only beginning to be elucidated. There is paucity of information on how implementation of pneumoperitoneum and head-up tilt under general anaesthesia affects CBF. This study was designed to observe changes that occur in the internal carotid artery (ICA) blood flow with pneumoperitoneum and head-up position and corelate these changes with changes in cardiac output in patients undergoing laparoscopic cholecystectomy.Methods: ICA blood velocity and diameter was measured by Doppler ultrasound in 35 ASA grade I and II patients undergoing laparoscopic cholecystectomy, at four time points: awake, after anaesthesia induction, after induction of pneumoperitoneum, and after head-up tilt; and ICA blood flow was calculated. Simultaneously, heart rate, blood pressure, and end-tidal carbon dioxide (ETCO2) were recorded, and cardiac output was calculated.Results: ICA blood flow decreased upon anesthesia induction from 164 mL/minute to 151 ml/minute (p&gt;0.05). ICA blood flow increased with pneumoperitoneum (from 164 mL/minute to 179ml/minute p= 0.04). Head-up tilt resulted in decrease in ICA blood flow (from 164 mL/minute to 151ml/ minute, P = 0.09).Conclusion: ICA blood flow significantly increased after the creation of pneumoperitoneum in patients undergoing elective laparoscopic cholecystectomy under general anaesthesia. Induction of anaesthesia and head-up tilt, however, did not have any significant change in ICA blood flow. We suggest that ICA blood flow during anaesthesia is influenced by an interplay of actions of anaesthetic agents, positive pressure ventilation and patient position besides the changes in blood pressure, ETCO2 and cardiac output.

Carbohydrate ingestion attenuates the reduction in complex cognitive function and cerebral blood flow during prolonged passive heat stress in humans

PurposeTo determine whether carbohydrate ingestion would reduce cognitive dysfunction in humans following long duration passive heat stress (PHS) versus consuming electrolytes alone. MethodsFifteen young (27 ± 4 y) healthy adults were exposed to 120 min of PHS through the use of a liquid perfused suit (50 °C) on two randomized visits. Subjects consumed fluids supplemented with electrolytes (E) or electrolytes + carbohydrates (E + C). Pre- and post-heat stress, body mass (BM) and plasma osmolality (pOsm) were measured. Heart rate (HR), blood pressure (BP), Physiological Strain Index (PSI), core temperature (Tc), plasma glucose, respiration rate (RR), end-tidal CO2 (PetCO2) and internal carotid artery (ICA) blood flow were recorded at baseline and every 15 min of heat stress. Cognitive function was assessed via the Automated Neuropsychological Assessment Metric at baseline and at 30- and 120 min during heat stress. ResultsThere were no significant differences between fluid conditions for BM, pOsm, PSI, Tc, RR or PetCO2. Plasma glucose was ∼75% greater in the E + C condition compared to the E condition after 90 min of PHS (P < 0.05). Cognitive function (120 min) was impaired following PHS only in E condition (P < 0.05) and performance on complex cognitive tasks were better by ∼22–340% in the E + C vs. E (P < 0.05). Compared to the E condition, HR and BP were lower and ICA blood flow, vascular conductance, and glucose delivery was ∼90% greater in the E + C after 90 min of PHS (P < 0.05). ConclusionsThese data are the first to demonstrate that carbohydrate ingestion may have a protective effect on cognitive function during long duration PHS. Furthermore, this protection was associated with preserved ICA blood flow and glucose delivery to the brain.

A machine learning approach to predict cerebral perfusion status based on internal carotid artery blood flow

Background and objectiveCerebral blood flow (CBF), or perfusion, is a prerequisite for maintaining brain metabolism and normal physiological functions. Diagnosing and evaluating cerebral perfusion status is crucial to managing brain disease. However, cerebral perfusion imaging devices are complicated to operate, should be controlled by specialized technicians, are often large, and are usually installed in fixed places such as hospitals. It is significantly difficult for clinicians to obtain the cerebral perfusion status in time. Considering that CBF is mainly supplied by the internal carotid artery (ICA), this study proposes a cerebral perfusion status prediction model that can automatically quantify the level of cerebral perfusion in patients by modeling the association between ICA blood flow and cerebral perfusion. Materials and methodsForty-eight participants were enrolled in the study after screening. We collected participants’ ICA ultrasound and brain magnetic resonance imaging (MRI) data before and after dobutamine injection based on a rigorous experimental paradigm and built an ICA-cerebral perfusion datasetdd. Support vector machine (SVM), k-nearest neighbor (KNN), decision tree (DT), random forest (RF), gradient boosting decision tree (GBDT), and extreme gradient boosting (XGBOOST) were used for early prediction of cerebral perfusion status. The SHAP analysis was adopted to reveal the impact of interpretable predictions for each feature. ResultsThe XGBOOST model demonstrated the best overall classification performance with an accuracy of 78.01%, sensitivity of 96.67%, specificity of 98.23%, F1 score of 74.57%, Matthews correlation coefficient (MCC) of 62.17%, and area under the receiver operating characteristic curve (AUC) of 87.08%. Accelerated speed, peak systolic flow velocity, and resistance index of ICA blood flow are important factors for cerebral perfusion prediction. ConclusionsThe proposed method paves a new avenue for the study of predicting cerebral perfusion status automatically and providesv a noninvasive, real-time, and low-cost alternative to brain perfusion imaging. Moreover, this analysis identifies highly predictive features for the cerebral perfusion status and gives clinicians an intuitive understanding of the influence of key features. The prediction models can serve as an early warning tool that offers sufficient time for clinicians to take early intervention measures.

Internal carotid artery blood flow and pulsatility index in cognitively impaired people with chronic heart failure.

Mild cognitive impairment and dementia are common and serious co-morbidities in people with chronic heart failure (HF) as they increase hospitalization rates, mortality and health care costs. Upon other factors, dysregulated cerebral perfusion might contribute to brain pathology. We aimed to evaluate the association of non-invasively measured blood flow (BF) and pulsatility index (PI) of the internal carotid artery (ICA) with (i) chronic HF parameters, (ii) brain morphologic measures and (iii) cognitive impairment. This post-hoc analysis of the observational, prospective Cognition.Matters-HF study included 107 chronic HF patients without atrial fibrillation or carotid artery stenosis (aged 63±10years; 19% women). Using extracranial sonography, we measured ICA-BF and ICA-PI 1.5cm distal of the carotid bifurcation. Brain magnetic resonance imaging was performed on a 3-Tesla scanner to quantify cerebral atrophy, hippocampal atrophy and white matter hyperintensities. Extensive neuropsychological testing tested the cognitive domains intensity of attention, visual/verbal memory and executive function (including its subdomains selectivity of attention, visual/verbal fluency and working memory) using a comprehensive test battery. (i) Neither ICA-BF (median 630 (quartiles 570, 700) mL/min) nor ICA-PI (1.05 (0.96. 1.23)) related to left ventricular ejection fraction, left atrial volume index or NT-proBNP. (ii) Higher ICA-PI (r=0.25; P=0.011), but not ICA-BF (r=0.08; P=0.409), associated with increased volume of white matter hyperintensities beyond ageing, while neither ICA-PI nor ICA-BF related to cerebral or hippocampal atrophy indices. (iii) ICA-BF, but not ICA-PI, positively correlated with age-adjusted T-scores of executive function (r=0.38; P<0.001) and its subdomains working memory (r=0.32; P<0.001) and visual/verbal fluency (r=0.32; P<0.001). In a multivariate linear model of executive function, only ICA-BF (T=3.79; P<0.001), but not HF or magnetic resonance imaging parameters, remained a significant correlate of executive function. ICA-BF and ICA-PI, measured in broadly available extracranial sonography, independently related to measures of functional and structural brain changes in people with chronic HF, respectively. Due to limitations of this cross-sectional approach without a healthy control group, larger controlled longitudinal studies are needed to further elucidate the role of ICA-BF dysregulation and its implication for clinical care in this vulnerable cohort.

Associations between Aortic Stiffness, Cerebral Artery Resistance and White Matter Integrity in Women with a History of Preeclampsia

Purpose: Preeclampsia is a pregnancy complication characterized by new-onset hypertension and systemic organ dysfunction. Women with a history of preeclampsia (hxPE) have a greater cerebral white matter ischemic damage burden and a three-fold elevated risk of vascular dementia later in life compared with healthy pregnancy independent of traditional cardiovascular risk factors. Aortic stiffness promotes the transmission of deleterious pulsatile pressure to the distal cerebral circulation, resulting in increased cerebrovascular resistance (CVR) that contributes to compromised brain blood flow and structure. We hypothesized that young women with hxPE would have greater aortic stiffness and CVR compared to healthy pregnancy, and CVR would be related to lower cerebral white matter microstructural integrity (WMI). Methods: Women with hxPE (N=10) were matched with healthy pregnancy controls (N=11) by age (28-42 years), educational attainment, body mass index, and postpartum duration (1-5 years). Aortic stiffness was quantified as carotid-femoral pulse wave velocity (CFPWV). 4D flow and diffusion tensor magnetic resonance images were acquired to evaluate internal carotid and middle cerebral artery (MCA) blood flow velocity and WMI (fractional anisotropy), respectively (3T MRI, GE). CVR index was calculated as the ratio of central mean arterial pressure to regional flow velocity. Results: Women with hxPE tended to exhibit higher CFPWV compared with controls (6.3±0.8 vs 5.6±0.7 m/s, P=0.09 adjusted for mean arterial pressure). CVR did not differ at the internal carotid artery (2.2±0.4 vs 2.0±0.3 mmHg s cm -1 , P=0.30) but was higher at the MCA among women with hxPE (2.4±0.3 vs 2.1±0.4 mmHg s cm -1 , P=0.08). In the entire group, CFPWV was associated with greater CVR at the internal carotid (r=0.41, P=0.07) and MCA (r=0.48, P=0.03). Although WMI did not differ between groups, greater MCA CVR was related to lower WMI overall (r=-0.45, P=0.049) and in select white matter tracts (corpus callosum genu, r=-0.53, P=0.02; cingulum hippocampus, r=-0.43, P=0.06; superior frontooccipital fasciculus, r=-0.46, P=0.04). Conclusions: Women with hxPE had elevated aortic stiffness that was associated with greater CVR. Greater CVR was related to lower WMI in subcortical watershed regions susceptible to reduced perfusion. These findings indicate that aortic stiffness may contribute to early declines in WMI via CVR in women with hxPE. Supported by AHA Transformational Project Award (969732) to GLP and NIH grant 1S10OD025025-01 to VM This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Cerebral blood flow response to cardiorespiratory oscillations in healthy humans

Dynamic cerebral autoregulation (CA) characterizes the cerebral blood flow (CBF) response to abrupt changes in arterial blood pressure (ABP). CA operates at frequencies below 0.15Hz. ABP regulation and probably CA are modified by autonomic nervous activity. We investigated the CBF response and CA dynamics to mild increase in sympathetic activity. Twelve healthy volunteers underwent oscillatory lower body negative pressure (oLBNP), which induced respiratory-related ABP oscillations at an average of 0.22Hz. We recorded blood velocity in the internal carotid artery (ICA) by Doppler ultrasound and ABP. We quantified variability and peak wavelet power of ABP and ICA blood velocity by wavelet analysis at low frequency (LF, 0.05-0.15Hz) and Mayer waves (0.08-0.12Hz), respectively. CA was quantified by calculation of the wavelet synchronization gamma index for the pair ABP-ICA blood velocity in the LF and Mayer wave band. oLBNP increased ABP peak wavelet power at the Mayer wave frequency. At the Mayer wave, ABP peak wavelet power increased by >70% from rest to oLBNP (p<0.05), while ICA blood flow velocity peak wavelet power was unchanged, and gamma index increased (from 0.49 to 0.69, p<0.05). At LF, variability in both ABP and ICA blood velocity and gamma index were unchanged from rest to oLBNP. Despite an increased gamma index at Mayer wave, ICA blood flow variability was unchanged during increased ABP variability. The increased synchronization during oLBNP did not cause less stable CBF or less active CA. Sympathetic activation seems to improve the mechanisms of CA.

Metformin effect on internal carotid artery blood flow assessed by area under the curve of carotid artery Doppler in women with polycystic ovarian syndrome.

Insulin resistance (IR) was reported in most polycystic ovarian syndrome (PCOS) cases. Metformin, a biguanide drug, successfully reduced IR. Homeostatic Model Assessment for IR (HOMA-IR) and Doppler parameters assessed metformin's effectiveness. To verify whether the area under the curve of the internal carotid artery (AUC-ICA) Doppler wave can be a useful marker for assessing IR among PCOS cases who presented with menstrual irregularity and were treated with metformin over 6 mo. An observational, cross-sectional study recruited 54 eligible PCOS women; the anthropometrics were as follows: age, body mass index (BMI), menstrual cycle days, biochemical serum cholesterol, low and high-density lipoprotein, sex hormone-binding globulin, fasting blood glucose, and HOMA-IR, hormonal testosterone, luteinizing hormone over follicle-stimulating hormone ratio, and ultrasonic pulsatility index (PI) and resistance index (RI), carotid artery intima-media thickness (CIMT) and (AUC-ICA) parameters were initially recorded and repeated 3 mo and 6 mo later with metformin tab 500 mg; three times/day for 6 mo. In addition, AUC-ICA was assessed by taking repeated systolic and diastolic wave height measurements. Metformin caused a progressive reduction in BMI, menstrual cycle days, biochemical hormonal, and Doppler parameters (CIMT, PI, RI, and AUC-ICA). AUC-ICA correlated strongly to all PCOS parameters. AUC-ICA correlated inversely with treatment time (r = -0.98, P < 0.001) and positively with HOMA-IR (r = 0.98, P < 0.0001). Via the best subset regression model, the AUC-ICA had the highest predictive value for HOMA-IR. AUC-ICA preceded PI, RI, and CIMT with a strong, meaningful correlation to all PCOS parameters, making it a reliable marker for the assessment of IR, especially during metformin therapy. Further studies are recommended to promote the application in practice.

The effect of a mesenteric traction syndrome on internal carotid artery blood flow

PurposeDuring abdominal surgery, manipulation of internal organs may induce a “mesenteric traction syndrome” (MTS) including a triad of flushing, hypotension, and tachycardia that lasts for approximately 30 min. We evaluated whether MTS affects internal carotid artery blood flow.MethodsThis prospective cohort study included 27 patients aged 65 ± 11 years (mean ± SD) undergoing stomach resection (n = 12), esophageal resection (n = 14), or gastro-entero anastomosis (n = 1) during propofol-remifentanil and thoracic epidural anesthesia. Duplex ultrasound determined internal carotid artery blood flow, laser Doppler flowmetry assessed forehead skin blood flow, and near-infrared spectroscopy determined cerebral oxygenation. Development of MTS was defined by flushing within 60 min after incision.ResultsSeven patients developed MTS 22 [20–26; median (IQR)] min after incision and at that time the change in heart rate (to 87 ± 13 vs. 70 ± 11 bpm; P = 0.0007) and skin blood flow (to 214 (134–269) vs. 84 (59-112 PU; P = 0.0044) was higher in the patients who developed MTS as compared to those who did not, while mean arterial pressure (63 ± 13 vs. 64 ± 14 mmHg; P = 0.1433), cerebral oxygenation (69 ± 9% vs. 63 ± 10%; P = 0.2485), and internal carotid artery flow (225 ± 53 vs. 203 ± 69 ml/min; P = 0.9529) were similar.ConclusionHemodynamic perturbations are observed in some patients in response to manipulation of the viscera, but the development of MTS appears not to influence internal carotid artery flow.Clinical trial registrationhttps://clinicaltrials.gov/ct2/show/NCT02951273?term=NCT02951273&amp;amp;rank=1, identifier: NCT02951273.

Assessment of extracranial carotid artery disease using digital twins – A pilot study

To improve risk stratification in extracranial internal carotid artery disease (CAD), patients who would benefit maximally from revascularization must be identified. In cardiology, the fractional flow reserve (FFR) has become a reference standard for evaluating the functional severity of coronary artery stenosis, and noninvasive surrogates thereof relying on computational fluid dynamics (CFD) have been developed. Here, we present a CFD-based workflow using digital twins of patients’ carotid bifurcations derived from computed tomography angiography for the noninvasive functional assessment of CAD. We reconstructed patient-specific digital twins of 37 carotid bifurcations. We implemented a CFD model using common carotid artery peak systolic velocity (PSV) acquired with Doppler ultrasound (DUS) as inlet boundary condition and a two-element Windkessel model as oulet boundary condition. The agreement between CFD and DUS on the PSV in the internal carotid artery (ICA) was then compared. The relative error for the agreement between DUS and CFD was 9% ± 20% and the intraclass correlation coefficient was 0.88. Furthermore, hyperemic simulations in a physiological range were feasible and unmasked markedly different pressure drops along two ICA stenoses with similar degree of narrowing under comparable ICA blood flow. Hereby, we lay the foundation for prospective studies on noninvasive CFD-based derivation of metrics similar to the FFR for the assessment of CAD.

Carbohydrate Ingestion Attenuates Cognitive Dysfunction Following Long-Duration Passive Heat Stress In Humans

PURPOSE: To determine if electrolyte or carbohydrate supplementation would reduce cognitive dysfunction in humans following long-duration passive heat stress. METHODS: Fifteen subjects performed 2 visits of 120 minutes of passive heat stress wearing liquid perfused suits infused with 50 °C water. In random order, subjects consumed fluids supplemented with electrolytes (E) or electrolytes+carbohydrates (E + C). Pre- and post-heat stress, body mass (BM) and plasma osmolality (pOsm) were measured. Heat rate, blood pressure, Physiological Strain Index (PSI), core temperature (TC), plasma glucose, plasma lactate, respiration rate, end-tidal CO2, internal carotid artery (ICA) velocity, and ICA diameter were recorded every 15 minutes. Cognitive function was assessed via the Automated Neurophysiological Assessment Metric (simple vs. complex cognitive tasks) at 30 minutes and at 120 minutes. RESULTS: There were no significant differences between fluid conditions (E & E + C) for BM loss (0.33 ± 0.2 & 0.22 ± 0.2 kg), pOsm (Δ3.6 ± 8.0 & 5.9 ± 6.7 mmol/L), peak-PSI (6.2 ± 0.3 & 5.9 ± 0.3), peak TC (38.9 ± 0.1 & 38.9 ± 0.1 °C), and ICA diameter (0.42 ± 0.01 & 0.42 ± 0.01 cm). Plasma glucose was significantly higher in the E + C condition at 60, 75, 90, 105, & 120 minutes (P < 0.05). No significant differences were noted between the 2 fluid conditions for the simple cognitive tasks however, in both fluid conditions, cognitive function was impaired following the bout of passive heat stress. Interestingly, compared to the E condition, the E + C condition demonstrated improved performance on all complex cognitive tasks (P < 0.05). Furthermore, compared to the E condition, the E + C condition demonstrated a significant increase in ICA blood velocity, blood flow, and vascular conductance at 90, 105, and 120 minute time points (P < 0.05) and a significant decrease in mean arterial pressure and heart rate at 60, 75, 90, 105, and 120 minute time points (P < 0.05). CONCLUSIONS: These data are the first to suggest that exogenous glucose administration may have a protective effect on cognitive function during long-duration passive heat stress. Furthermore, this protection is associated with elevated global cerebral blood flow and glucose delivery to the brain.