Carotid Arterial Pressure Research Articles

Patients with amnestic mild cognitive impairment have higher cerebrovascular impedance than cognitively normal older adults.

Brain hypoperfusion is associated with cognitive impairment. Higher cerebrovascular impedance modulus (Z) may contribute to brain hypoperfusion. We tested hypotheses that patients with amnestic mild cognitive impairment (aMCI) (i.e., those who have a high risk of developing Alzheimer's disease) have higher Z than age-matched cognitively normal individuals, and that high Z is correlated with brain hypoperfusion. Fifty-eight patients with aMCI (67 ± 7 yr) and 25 cognitively normal subjects (CN, 65 ± 6 yr) underwent simultaneous measurements of carotid artery pressure (CAP, via applanation tonometry) and middle cerebral arterial blood velocity (CBV, via transcranial Doppler). Z was quantified using cross-spectral and transfer function analyses between dynamic changes in CBV and CAP. Patients with aMCI exhibited higher Z than NC (1.18 ± 0.34 vs. 1.01 ± 0.35 mmHg/cm/s, P = 0.044) in the frequency range from 0.78 to 4.29 Hz. The averaged Z in the frequency range (0.78-3.13 Hz) of high coherence (>0.9) was inversely correlated with total cerebral blood flow measured with 2-D Doppler ultrasonography normalized by the brain tissue mass (via structural MRI) across both patients with aMCI and NC (r = -0.311, P = 0.007), and in patients with aMCI alone (r = -0.306, P = 0.007). Our findings suggest that patients with aMCI have higher cerebrovascular impedance than cognitively normal older adults and that increased cerebrovascular impedance is associated with brain hypoperfusion.NEW & NOTEWORTHY This is the first study to compare cerebrovascular impedance between patients with amnestic mild cognitive impairment (aMCI) and age-matched cognitively normal individuals. Patients with aMCI had higher cerebrovascular impedance modulus than age-matched cognitively normal individuals, which was correlated with brain hypoperfusion. These results suggest the presence of cerebrovascular dysfunction in the dynamic regulation of cerebral blood flow in older adults who have high risks of Alzheimer's disease.

Evaluation of Cognitive and Biochemical Brain Status in Patients after Carotid Endarterectomy

INTRODUCTION: In the large studies such as NASCET, ESCT, VACS, ACAS and ACST-1, the role of alteration of the cognitive functions of a patient in the early and long-term postoperative periods have not been determined.
 AIM: To evaluate the biochemical parameters of cerebral functions, the cognitive status of patients, and their interrelation after carotid endarterectomy.
 MATERIALS AND METHODS: The study involved 60 patients divided into two groups. The mean age was 67.3 ± 7.9 years, there were 49 (81%) men and 19 (19%) women. Group A included ‘symptomatic’ patients (n = 30) who underwent carotid endarterectomy and had a history of an acute cerebrovascular event. Group B included ‘asymptomatic’ patients (n = 30) who underwent carotid endarterectomy but had no history of cerebrovascular events. As part of the study, the following data were evaluated within a 6-month period: cognitive status (on MMSE, FAB, MoCA-test, NIHSS scales), biochemical parameters (S100b protein, neuron specific enolase (NSE), brain derived neurotrophic growth factor (BDNF)) and the ultrasound data of the carotid arteries.
 RESULTS: Patients of group A showed improvement of the cognitive status by the 6th month on MMSE scale (p = 0.001) and in MoCA-test (p = 0.09) relative to the initial parameters; on FAB scale relative to the data after 1 month (p = 0.01); a decline of the level of neurological deficit on NIHSS scale (p = 0.01). In group A, an inverse correlation was found between the results on MMSE scale and resistance index (r = -0.675; p = 0.005), and a direct correlation between the results on FAB scale and the end diastolic pressure in the internal carotid artery (r = +0.912; p = 0.005) according to the ultrasound data. The data obtained in group B, reflected improvement of the cognitive status by the 6th month only by 2 points on MoCA test (p = 0. 03) relative to the initial data. Besides, in 6 months after the surgery, there was a 2-fold increase in S100b marker (p = 0.01) and NSE protein (p = 0.02) and a 1.5-fold increase in BDNF protein as compared to the initial values (p = 0.005).
 CONCLUSIONS: Carotid endarterectomy leads to improvement of the cognitive status evaluated on MMSE, FAB, MoCA, NIHSS scales in the long-term postoperative period in symptomatic patients. The extent of improvement of neuropsychological status depends on the level of the end diastolic pressure and resistance index in the internal carotid artery on the operated side.

Autoregulated and Non-Autoregulated Blood Flow Restriction on Acute Arterial Stiffness.

This study aimed to investigate the acute effects of autoregulated and non-autoregulated applied pressures during blood flow restriction resistance exercise to volitional fatigue on indices of arterial stiffness using the Delfi Personalized Tourniquet System. Following a randomized autoregulated or non-autoregulated blood flow restriction familiarization session, 20 physically active adults (23±5 years; 7 females) participated in three randomized treatment-order sessions with autoregulated and non-autoregulated and no blood flow restriction training. Participants performed four sets of dumbbell wall squats to failure using 20% of one repetition maximum. Blood flow restriction was performed with 60% of supine limb occlusion pressure. Testing before and post-session included an ultrasonic scan of the carotid artery, applanation tonometry, and blood pressure acquisition.Carotid-femoral pulse wave velocity increased in the non-autoregulated and no blood flow restriction training groups following exercise while carotid-radial pulse wave velocity increased in the no blood flow restriction training group (all p<0.05). Carotid-femoral pulse wave velocity exhibited an interaction effect between autoregulated and non-autoregulated blood flow restriction in favor of autoregulated blood flow restriction (p<0.05). Autoregulated blood flow restriction training does not influence indices of arterial stiffness while non-autoregulated and no blood flow restriction training increases central stiffness.

Non-contact quantification of aortic stenosis and mitral regurgitation using carotid waveforms from skin displacements.

Objective. Early diagnosis of heart problems is essential for improving patient prognosis.Approach. We created a non-contact imaging system that calculates the vessel-induced deformation of the skin to estimate the carotid artery pressure displacement waveforms. We present a clinical study of the system in patients (n= 27) with no underlying condition, aortic stenosis (AS), or mitral regurgitation (MR).Main results. Displacement waveforms were compared to aortic catheter pressures in the same patients. The morphologies of the pressure and displacement waveforms were found to be similar, and pulse wave analysis metrics, such as our modified reflection indices (RI) and waveform duration proportions, showed no significant differences. Compared with the control group, AS patients displayed a greater proportion of time to peak (p= 0.026 andp= 0.047 for catheter and displacement, respectively), whereas augmentation index (AIx)was greater for the displacement waveform only (p= 0.030). The modified RI for MR (p= 0.047 andp= 0.004 for catheter and displacement, respectively) was lower than in the controls. AS and MR were also significantly different for the proportion of time to peak (p= 0.018 for the catheter measurements), RI (p= 0.045 andp= 0.002 for the catheter and displacement, respectively), and AIx (p= 0.005 for the displacement waveform).Significance. These findings demonstrate the ability of our system to provide insights into cardiac conditions and support further development as a diagnostic/telehealth-based screening tool.

Carotid Stenting Can Improve Contralateral Perfusion and Function

For patients with carotid artery stenosis, carotid endarterectomy and carotid angioplasty and stenting are two methods that are effective in reducing stroke risk. These procedures have also been known to increase perfusion to the ipsilateral hemisphere and improve function; however, it is unknown if these procedures can improve function by increasing perfusion to the contralateral hemisphere. Longitudinal language assessment and neuroimaging data from this case study offers evidence that supports stenting of the contralateral common carotid artery and blood pressure elevation to improve collateral blood flow and, in turn, language performance.

A HEAD-TO-HEAD COMPARISON OF PULSE TRANSIT TIME USING SECOND-DERIVATIVE AND INTERSECTING TANGENTS METHODS

Objective: Determination of aortic stiffness as measured by carotid-femoral pulse wave velocity (CFPWV) is based on pulse transit time (PTT). PTT is determined by identification of the foot of the pressure wave using either the peak of the second-derivative or the intersecting tangents algorithm. The aim of this study was to examine if there are any differences when these algorithms are performed on the same arterial pressure waveforms. Design and method: Carotid and femoral arterial pressure waveforms were simultaneously recorded using the piezoelectric sensors of the Complior Analyse system. Waveforms were extracted and imported into In-house software (MATLAB; MathWorks, Natick, Massachusetts, USA) to calculate the PTT only on valid pressure waveforms without artifacts that are due to movements. Results: In 105 human subjects (59 ± 18 years; 64% men) including a mix of 59% hypertensive, 34% with chronic kidney disease, 16% diabetic and 13% with cardiovascular disease, the average brachial blood pressure was 125 ± 18/73 ± 10 mmHg. A total of 6 203 pairs of simultaneous carotid and femoral arterial pressure waveforms were analysed. The PTT using the second-derivative algorithm was 68.4 ± 18.6 ms (CFPWV: 9.48 ± 3.18 m/s), similar to PTT using the intersecting tangents method that was 68.6 ± 18.8 (CFPWV: 9.45 ± 3.12). This difference while statistically significant given the high number of observation points (P &lt; 0.001), is not considered to be clinically significant. Conclusions: Based on our findings, both algorithms perform similarly and can be used interchangeably when high quality acquisition are used. However, device-based algorithms may perform differently given variabilities in quality assessment criteria.

Lung aeration reduces blood pressure surges caused by umbilical cord milking in preterm lambs.

Umbilical cord milking (UCM) at birth causes surges in arterial blood pressure and blood flow to the brain, which may explain the high risk of intraventricular haemorrhage (IVH) in extremely preterm infants receiving UCM. This high risk of IVH has not been reported in older infants. We hypothesized that lung aeration before UCM, reduces the surge in blood pressure and blood flow induced by UCM. At 126 days' gestation, fetal lambs (N = 8) were exteriorised, intubated and instrumented to measure umbilical, pulmonary, cerebral blood flows, and arterial pressures. Prior to ventilation onset, the umbilical cord was briefly (2-3 s) occluded (8 times), which was followed by 8 consecutive UCMs when all physiological parameters had returned to baseline. Lambs were then ventilated. After diastolic pulmonary blood flow markedly increased in response to ventilation, the lambs received a further 8 consecutive UCMs. Ovine umbilical cord is shorter than the human umbilical cord, with ∼10 cm available for UCMs. Therefore, 8 UCMs/occlusions were done to match the volume reported in the human studies. Umbilical cord clamping occurred after the final milk. Both umbilical cord occlusions and UCM caused significant increases in carotid arterial blood flow and pressure. However, the increases in systolic and mean arterial blood pressure (10 ± 3 mmHg vs. 3 ± 2 mmHg, p = 0.01 and 10 ± 4 mmHg vs. 6 ± 2 mmHg, p = 0.048, respectively) and carotid artery blood flow (17 ± 6 ml/min vs. 10 ± 6 ml/min, p = 0.02) were significantly greater when UCM occurred before ventilation onset compared with UCM after ventilation. UCM after ventilation onset significantly reduces the increases in carotid blood flow and blood pressure caused by UCM.

Results of carotid endarterectomy with the use of temporary shunts with reduced retrograde pressure in the internal carotid artery - analysis of the multicenter Russian register.

The aim of the study was to assess the role of a temporary carotid shunt in patients undergoing carotid endarterectomy. This was a retrospective, multicentric (n = 159) study carried out between January 2005 and October 2020. The study included 3114 patients undergoing carotid endarterectomy who had a reduced retrograde internal carotid artery pressure (<60% of systolic blood pressure). A temporary carotid shunt was used in 1328 patients and 1786 patients underwent carotid endarterectomy without a shunt. The in-hospital outcomes were comparable in terms of the incidence of deaths, myocardial infarctions, and stroke between the two groups. However, asymptomatic strokes (confirmed on computed tomography) occurred more frequently in the group where the temporary shunt was used (34 (2.5%) vs. 10 (0.55%), p < 0.0001). The composite endpoints of adverse events were also higher in the group where a temporary shunt was used (44 (3.3%) vs. 28 (1.5%), p = 0.002). The risk of symptomatic stroke (both fatal and non-fatal) was higher in the group where a temporary shunt was not used, though this was statistically not significant. Logistic regression analysis identified diabetes mellitus and stenosis (81-90%) of the contralateral internal carotid artery to be important predictors for stroke. Temporary carotid shunts during carotid endarterectomy were associated with increased rates of asymptomatic stroke. There were no statistically significant differences in the incidence of non-fatal or fatal stroke, myocardial infarction, and mortality.

Comparison of hemodynamic indices of dialysis patients in continuous renal replacement therapy and intermittent renal replacement therapy methods with ultrasonic cardiac output monitor in intensive care unit

Introduction: Acute kidney injury (AKI) is a common complication in the intensive care unit (ICU) and is independently associated with end-stage renal disease and higher mortality in the ICU. There are different methods to supporting kidney function in critically ill patients. The renal replacement therapy (RRT) can be conducted continuously, intermittently, or in combination. Objectives: The purpose of our study is to investigate the hemodynamic indices of dialysis patients in the ICU by two methods high flow continuous renal replacement therapy (CRRT) and intermittently renal replacement therapy (IRRT) of ultrasonic cardiac output monitor (USCOM). Patients and Methods: In this study conducted at Sina hospital, patients requiring dialysis hospitalized to the ICU were studied. Around 48 patients benefited from rapid CRRT or IRRT in the opinion of a specialist. Basic patient information was recorded. To check hemodynamic parameters during dialysis, USCOM was carried out to check corrected flow time value (FTc) parameters, systemic vascular resistance (SVR) and cardiac output. Results were compared between the IRRT and CRRT groups. Results: This study was conducted on 48 patients who were candidates for dialysis. Patients were divided into high flow CRRT and IRRT groups based on clinical indications. In CRRT group, 19 patients (79.2%) and in the IRRT group, 20 patients (83.3%) were male (P=0.712). Their mean age was 68.70 ± 8.25 years in the CRRT group and 68.58 ± 7.19 years in the IRRT group. All patients had cardiac output monitored using USCOM or ultrasound. The mean Sequential Organ Failure Assessment (SOFA) score in the CRRT group was 7 and in the IRRT group was 6, with no significant difference among them. FTc value variable or modified flow time in the carotid artery, cardiac output, cardiac index, SVR variable and mean arterial pressure in in the two groups at four evaluated times (before dialysis, 15 minutes later, one hour later and end of dialysis) from the study the difference were not statistically significant. Conclusion: Although previos studies have recommended CRRT, our study showed significant difference may not be existed between IRRT and CRRT.

Sex-specific associations of reservoir-excess pressure parameters with age and subclinical vascular remodeling.

Central artery reservoir pressure and excess pressure (XSP) are associated with cardiovascular disease (CVD) events and mortality. However, sex differences in the trajectory of central reservoir pressure and XSP with advancing age and their relations with vascular markers of subclinical CVD risk are incompletely understood. Therefore, we tested the hypothesis that central reservoir pressure and XSP would be positively associated with advancing age and vascular markers of subclinical CVD risk in men and women. Healthy adults ( n = 398; aged 18-80 years, 60% female individuals) had central (carotid) artery pressure waveforms acquired by applanation tonometry. Reservoir pressure and XSP peaks and integrals were derived retrospectively from carotid pressure waveforms using custom written software. Carotid artery intimal-medial thickness (IMT) was measured by ultrasonography, and aortic stiffness was determined from carotid-femoral pulse wave velocity (cfPWV). Reservoir pressure peak, reservoir pressure integral and XSP integral were higher with age in both men and women ( P < 0.05), whereas XSP peak was lower with age in men ( P < 0.05). In women, both reservoir pressure peak ( β = 0.231, P < 0.01) and reservoir pressure integral ( β = 0.254, P < 0.01) were associated with carotid artery IMT, and reservoir pressure peak was associated with cfPWV ( β = 0.120, P = 0.02) after adjusting for CVD risk factors. Central artery reservoir pressure and XSP were higher with advancing age in men and women, and reservoir pressure peak was associated with both carotid artery wall thickness and aortic stiffness in women but not men. Central reservoir pressure peak may provide some insight into sex differences in vascular remodeling and subclinical CVD risk with advancing age in healthy adults.

Lipid profile peculiarities and matrix Gla protein concentration in Ukrainian pediatric patients with heterozygous familial hypercholesterolemia

Atherosclerotic changes in the vascular walls begin early in childhood, especially in association with familial hypercholesterolemia (FH). The process may be subclinical, which nevertheless requires therapeutic and preventive measures. Purpose - to evaluate baseline lipid profiles, the thickness of carotid intima-media complexes, blood pressure indices and the association with concentration changes of dephosphorylated-uncarboxylated matrix Gla protein (dp-uc MGP) as a marker of subclinical arterial lesions in different age groups of pediatric patients with FH. Materials and methods. Children with heterozygous FH (n=15), stratified by age and sex, were included in the study. The control group consisted of healthy peers (n=21). Blood samples were analyzed to determine levels of total (TC), low-density (LDL-C), very-low-density (VLDL-C), high-density (HDL-C), remnant (rC) and non-high-density (non-HDL-C) cholesterol, triglycerides (TG), apolipoproteins A1 (apoA1) and B (apoB), lipoprotein (a), and dp-uc MGP. The intima-media complex thickness of the common carotid artery and blood pressure were measured in all study subjects. The obtained data were processed using the accepted methods of medical statistics and SAS® OnDemand for Academics. Results. Lipid profile changes in pediatric patients with FH were characterized by high levels of LDL-C, non-HDL-C and lipoprotein (a) in the 5-9 years age group; in the 10-14 years age group - high levels of LDL-C, TG, rC, non-HDL-C and lipoprotein (a); in the 15-18 years age group - high levels of LDL-C, TG, non-HDL-C and lipoprotein (a). At the same time, the most marked dyslipidemia changes were evident in children aged 10-14 years in the FH group. apoA1 levels were significantly decreased in all FH children. Elevated levels of lipoprotein (a) (&gt;30 mg/dL) in FH children were found in all age groups, suggesting that elevated lipoprotein (a) levels can be used as a factor for cardiovascular risk stratification. Dp-uc MGP levels were significantly elevated in all age groups of FH children compared to healthy peers. Conclusions. A lipid profile examination is necessary to diagnose FH in children, along with family health history and cascade screening. As atherosclerotic changes at 5-18 years of age remain subclinical, and the instrumental tests available in routine medical practice are not sensitive enough to detect them, therefore, preventive or therapeutic measures cannot be initiated promptly. The evaluation of circulating matrix Gla protein in pediatric patients with FH can be used as a marker of vascular wall calcification, which may allow early preventive measures against microcalcification to be developed. The research was carried out in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the Local Ethics Committee of the participating institution. The informed consent of the patient was obtained for conducting the studies. No conflict of interests was declared by the authors.

Abstract 211: Epinephrine Does Not Correct Post-ROSC Hypoperfusion Despite Normalizing Blood Pressure A Rat Model Of Severe Pediatric Asphyxial Cardiac Arrest

In children resuscitated from cardiac arrest, systemic hypotension occurs frequently and is associated with worse outcome. The first-line vasoactive treatment for post-arrest hypotension is continuous infusion of epinephrine. Epinephrine dose is titrated to maintain normal blood pressure for age. Epinephrine, however, also leads to vasoconstriction which may impair organ perfusion after resuscitation.We hypothesized that epinephrine infusion during the post-resuscitation period restores systemic blood pressure but not flow to vital organs. Using a model of severe pediatric asphyxial cardiac arrest in developing rats, we simultaneously measured blood pressure (ABP) and flow in carotid (Fc) and femoral (Ff) arteries after resuscitation. We then compared the effects of epinephrine or saline infusions on blood pressure vs flow. One hour after resuscitation from 11.5 minutes of asphyxial arrest, ABP, Fc and Ff were 61.73 ± 2.68; 42.58 ± 3.84; and 19.53 ± 7.00 % of baseline. Epinephrine infusion increased ABP in a dose-dependent manner, reaching 95.13 ± 7.93 % of baseline at 0.5 μg/kg/min. Saline infusion at equivalent volumes increased ABP only marginally to 69.88 ± 2.60 % of baseline. In contrast to its effect on ABP, epinephrine infusion increased Fc only to 49.55 ± 6.49 and Ff to 53.28 ± 7.13 % of baseline. Saline infusion at equivalent volumes, on the other hand, had a more salutary effect than epinephrine on improving blood flow (Fc 64.62 ± 6.64 and Ff 60.25 ± 7.60 % of baseline). Notably, a single 10 cc/kg saline bolus, administered when ABP decreased to ~80% of baseline post-ROSC, increased blood flow and ABP to 100% and 90% of baseline, respectively. These data indicate that epinephrine infusion in the post-arrest period adversely affects arterial blood flow despite normalizing arterial blood pressure. Continued fluid resuscitation with crystalloids potentially has beneficial effect on correcting post-ROSC hypoperfusion. Future studies need to explore the impact of targeting flow rather than blood pressure in the post-arrest period and its association to post-arrest end-organ function in children.

A hydroalcoholic extract of Senecio nutans SCh. Bip (Asteraceae); its effects on cardiac function and chemical characterization

Ethnopharmacology relevanceThe plant Senecio nutans SCh. Bip. is used by Andean communities to treat altitude sickness. Recent evidence suggests it may produce vasodilation and negative cardiac inotropy, though the cellular mechanisms have not been elucidated. PurposeTo determinate the mechanisms action of S. nutans on cardiovascular function in normotensive animals. MethodsThe effect of the extract on rat blood pressure was measured with a transducer in the carotid artery and intraventricular pressure by a Langendorff system. The effects on sheep ventricular intracellular calcium handling and contractility were evaluated using photometry. Ultra-high-performance liquid-chromatography with diode array detection coupled with heated electrospray-ionization quadrupole-orbitrap mass spectrometric detection (UHPLC-DAD-ESI-Q-OT-MSn) was used for extract chemical characterization. ResultsIn normotensive rats, S. nutans (10 mg/kg) reduced mean arterial pressure (MAP) by 40% (p < 0.05), causing a dose-dependent coronary artery dilation and decreased left ventricular pressure. In isolated cells, S. nutans extract (1 μg/ml) rapidly reduced the [Ca2+]i transient amplitude and sarcomere shorting by 40 and 49% (p < 0.001), respectively. The amplitude of the caffeine evoked [Ca2+]i transient was reduced by 24% (p < 0.001), indicating reduced sarcoplasmic reticulum (SR) Ca2+ content. Sodium-calcium exchanger (NCX) activity increased by 17% (p < 0.05), while sarcoendoplasmic reticulum Ca2+-ATPase (SERCA) activity was decreased by 21% (p < 0.05). LC-MS results showed the presence of vitamin C, malic acid, and several antioxidant phenolic acids reported for the first time. Dihydroeuparin and 4-hydroxy-3-(3-methylbut-2-enyl) acetophenone were abundant in the extract. ConclusionIn normotensive animals, S. nutans partially reduces MAP by decreasing heart rate and cardiac contractility. This negative inotropy is accounted for by decreased SERCA activity and increased NCX activity which reduces SR Ca2+ content. These results highlight the plant's potential as a source of novel cardio-active phytopharmaceuticals or nutraceuticals.

Aerobic exercise training reduces cerebrovascular impedance in older adults: a 1-year randomized controlled trial.

Older adults have higher cerebrovascular impedance than young individuals which may contribute to chronic brain hypoperfusion. Besides, middle-aged athletes exhibit lower cerebrovascular impedance than their sedentary peers. We examined whether aerobic exercise training (AET) reduces cerebrovascular impedance in sedentary older adults. We conducted a proof-of-concept trial that randomized 73 older adults to 1 yr of AET (n = 36) or stretching and toning (SAT, n = 37) interventions. Cerebrovascular impedance was estimated from simultaneous recordings of carotid artery pressure (CAP) via applanation tonometry and cerebral blood flow velocity (CBFV) in the middle cerebral artery via transcranial Doppler using transfer function analysis. Fifty-six participants completed 1-yr interventions, and 41 of those completed cerebrovascular impedance measurements. AET group showed a significant increase in V̇o2peak after the intervention [estimated marginal mean (95% confidence interval); from 22.8 (21.6 to 24.1) to 24.9 (23.6 to 26.2) mL·kg-1·cm-1, P < 0.001], but not SAT [from 21.7 (20.5 to 22.9) to 22.3 (21.1 to 23.7) mL·kg-1·cm-1, P = 0.114]. Coherence between changes in CBFV and CAP was >0.90 in the frequency range of 0.78-3.12 Hz. The averaged cerebrovascular impedance modulus (Z) in this frequency range decreased after 1-yr AET [from 1.05 (0.96 to 1.14) to 0.95 (0.92 to 1.06) mmHg·s·cm-1, P = 0.023], but not SAT [from 0.96 (0.87 to 1.04) to 1.01 (0.92 to 1.10) mmHg·s·cm-1, P = 0.138]. Reductions in Z were correlated positively with reductions in carotid pulse pressure (r = 0.628, P = 0.004) and inversely with mean CBFV (r = -0.563, P = 0.012) in the AET group. One-year AET reduces cerebrovascular impedance in older adults, which may benefit brain perfusion.NEW & NOTEWORTHY Estimation of cerebrovascular impedance is essential for understanding dynamic cerebral blood flow regulation. This randomized controlled trial demonstrated that aerobic exercise training reduced cerebrovascular impedance in older adults, which may benefit brain perfusion.

Role of the angiotensin type 1 receptor in modulating the carotid chemoreflex in an ovine model of renovascular hypertension.

The carotid body has been implicated as an important mediator and putative target for hypertension. Previous studies have indicated an important role for angiotensin II in mediating carotid body function via angiotensin type-1 receptors (AT1R); however, their role in modulating carotid body function during hypertension is unclear. Using a large preclinical ovine model of renovascular hypertension, we hypothesized that acute AT1R blockade would lower blood pressure and decrease carotid body-mediated increases in arterial pressure. Adult ewes underwent either unilateral renal artery clipping or sham surgery. Two weeks later, flow probes were placed around the contralateral renal and common carotid arteries. In both hypertensive and sham animals, carotid body stimulation using potassium cyanide caused dose-dependent increases in mean arterial pressure but a reduction in renal vascular conductance. These responses were not different between groups. Infusion of angiotensin II led to an increase in arterial pressure and reduction in renal blood flow. The sensitivity of the renal vasculature to angiotensin II was significantly attenuated in hypertension compared with the sham animals. Systemic inhibition of the AT1R did not alter blood pressure in either group. Interestingly carotid body-evoked arterial pressure responses were attenuated by AT1R blockade in renovascular hypertension but not in shams. Taken together, our findings indicate a decrease in vascular reactivity of the non-clipped kidney to angiotensin II in hypertension. The CB-evoked increase in blood pressure in hypertension is mediated in part, by the AT1R. These findings indicate a differential role of the AT1R in the carotid body versus the renal vasculature.

Influence of postural changes on haemodynamics in internal carotid artery bifurcation aneurysm using numerical methods

Cerebral intracranial aneurysms are serious problems that can lead to stroke, coma, and even death. The effect of blood flow on cerebral aneurysms and their relationship with rupture are unknown. In addition, postural changes and their relevance to haemodynamics of blood flow are difficult to measure in vivo using clinical imaging alone. Computational simulations investigating the detailed haemodynamics in cerebral aneurysms have been developed in recent times not only to understand the progression and rupture but also for clinical evaluation and treatment. In the present study, the haemodynamics of a patient-specific case of a large aneurysm on the left side internal carotid bifurcation (LICA) and no aneurysm on the right side internal carotid bifurcation (RICA) was investigated. The simulation of these patient-specific models using fluid–structure interaction provides a valuable comparison of flow behavior between normal and aneurysm models. The influences of postural changes were investigated during standing, sleeping, and head-down (HD) position. Significant changes in flow were observed during the HD position and quit high arterial blood pressure in the internal carotid artery (ICA) aneurysm model was established when compared to the normal ICA model. The velocity increased abruptly during the HD position by more than four times (LICA and RICA) and wall shear stress by four times (LICA) to ten times (RICA). The complex spiral flow and higher pressures prevailing within the dome increase the risk of aneurysm rupture.

The Sheep as a Comprehensive Animal Model to Investigate Interdependent Physiological Pressure Propagation and Multiparameter Influence on Cerebrospinal Fluid Dynamics.

The present study aims to develop a suitable animal model for evaluating the physiological interactions between cerebrospinal fluid (CSF) dynamics, hemodynamics, and abdominal compartment pressures. We seek to contribute to the enhanced recognition of the pathophysiology of CSF-dependent neurological disorders like hydrocephalus and the improvement of available treatment options. To date, no comprehensive animal model of CSF dynamics exists, and establishing an accurate model will advance our understanding of complex CSF physiology. Persisting knowledge gaps surrounding the communication and pressure propagation between the cerebrospinal space and adjacent anatomical compartments exacerbate the development of novel therapies for neurological diseases. Hence, the need for further investigation of the interactions of vascular, craniospinal, and abdominal pressures remains beyond dispute. Moreover, the results of this animal study support the optimization of in vitro test benches for medical device development, e.g., ventriculoperitoneal shunts. Six female white alpine sheep were surgically equipped with pressure sensors to investigate the physiological values of intracranial, intrathecal, arterial, central venous, jugular venous, vesical pressure, and four differently located abdominal pressures. These values were measured simultaneously during the acute animal trial with sheep under general anesthesia. Both carotid and femoral arterial blood pressure indicate a reliable and comparable representation of the systematic blood pressure. However, the jugular venous pressure and the central venous pressure in sheep in dorsal recumbency do not correlate well under general anesthesia. Furthermore, there is a trend for possible comparability of lateral intraventricular and lumbar intrathecal pressure. Nevertheless, animal body position during measurements must be considered since different body constitutions can alter the horizontal line between the cerebral ventricles and the lumbar subarachnoid space. While intra-abdominal pressure measurement in the four different abdominal quadrants yielded greater inter-individual variability, intra-vesical pressure measurements in our setting delivered comparable values for all sheep. We established a novel and comprehensive ovine animal model to investigate interdependent physiologic pressure propagation and multiparameter influences on CSF dynamics. The results of this study will contribute to further in vitro bench testing, the derivation of novel quantitative models, and the development of a pathologic ovine hydrocephalus model.

Carotid Reservoir Pressure Decrease After Prolonged Head Down Tilt Bed Rest in Young Healthy Subjects Is Associated With Reduction in Left Ventricular Ejection Time and Diastolic Length.

BackgroundThe arterial pressure waveform reflects the interaction between the heart and the arterial system and carries potentially relevant information about circulatory status. According to the commonly accepted ‘wave transmission model’, the net BP waveform results from the super-position of discrete forward and backward pressure waves, with the forward wave in systole determined mainly by the left ventricular (LV) ejection function and the backward by the wave reflection from the periphery, the timing and amplitude of which depend on arterial stiffness, the wave propagation speed and the extent of downstream admittance mismatching. However, this approach obscures the ‘Windkessel function’ of the elastic arteries. Recently, a ‘reservoir-excess pressure’ model has been proposed, which interprets the arterial BP waveform as a composite of a volume-related ‘reservoir’ pressure and a wave-related ‘excess’ pressure.MethodsIn this study we applied the reservoir-excess pressure approach to the analysis of carotid arterial pressure waveforms (applanation tonometry) in 10 young healthy volunteers before and after a 5-week head down tilt bed rest which induced a significant reduction in stroke volume (SV), end-diastolic LV volume and LV longitudinal function without significant changes in central blood pressure, cardiac output, total peripheral resistance and aortic stiffness. Forward and backward pressure components were also determined by wave separation analysis.ResultsCompared to the baseline state, bed rest induced a significant reduction in LV ejection time (LVET), diastolic time (DT), backward pressure amplitude (bP) and pressure reservoir integral (INTPR). INTPR correlated directly with LVET, DT, time to the peak of backward wave (bT) and stroke volume, while excess pressure integral (INTXSP) correlated directly with central pressure. Furthermore, Δ.INTPR correlated directly with Δ.LVET, and Δ.DT, and in multivariate analysis INTPR was independently related to LVET and DT and INTXSP to central systolic BP.ConclusionThis is an hypothesis generating paper which adds support to the idea that the reservoir-wave hypothesis applied to non-invasively obtained carotid pressure waveforms is of potential clinical usefulness.

Temporary shunt and carotid endarterectomy (review of literature)

The main idea of this article is based on the uncertainty of the current recommendations, according to which a temporary shunt (TS) during carotid endarterectomy (CEE) can be used selectively, routinely, and even completely abandon its use. This statement is supported by the low level of evidence (class B) of the conclusion that indications for the use of TS are established only on the basis of a decrease in retrograde pressure in the internal carotid artery (ICA) and/or indicators of cerebral oximetry. Thus, the low efficiency of these procedures makes it possible not to use them at all.

Establishing a Multidisciplinary Cavernous Carotid Injury Simulation to Train Neurosurgical, Otolaryngology, and Anesthesia Residents.

Carotid artery injuries are serious complications of endoscopic endonasal surgery. As these occur rarely, simulation training offers an avenue for technique and algorithm development in resident learners. This study develops a realistic cadaveric model for the training of crisis resource management in the setting of cavernous carotid artery injury. An expanded endonasal approach and right cavernous carotid injury is performed on a cadaveric head. The cadaver's right common carotid artery is cannulated and connected to a perfusion pump delivering pressurized simulated blood. A simulation mannequin is incorporated into the model to allow for vital sign feedback. Surgical and anesthesia resident learners are tasked with obtaining vascular control with a muscle patch technique and medical management over the course of 3 clinical scenarios with increasing complexity. Crisis management instructions for an endoscopic endonasal approach to the cavernous carotid artery and blood pressure control were provided to the learners prior to beginning the simulation. An independent reviewer evaluated the learners on communication skills, crisis management algorithms, and implementation of appropriate skill sets. After each scenario, residents were debriefed on how to improve technique based on evaluation scores in areas of situational awareness, decision-making, communications and teamwork, and leadership. After the simulation, learners provided feedback on the simulation and this data was used to improve future simulations. The benefit of this cadaveric model is ease of set-up, cost-effectiveness, and reproducibility.