Angiotensin II acutely increases arterial stiffness as monitored by cardio-ankle vascular index (CAVI) in anesthetized rabbits

Evaluating the relationship between ocular blood flow and systemic organ blood flow in hemorrhagic shock using a rabbit model

This study aimed to investigate the feasibility of utilizing noninvasive ocular blood flow measurements as potential indicators of systemic circulation in rabbits experiencing hemorrhagic shock. Using Laser speckle flowgraphy, ocular blood flow indices, relative flow volume (RFV), and mean blur rate in the choroidal area (MBR-CH) were assessed in New Zealand White rabbits (n = 10) subjected to controlled blood removal and return. Hemodynamic parameters and biochemical markers were monitored alongside ocular circulation during blood removal and return phases. Additionally, correlations between ocular parameters and systemic indices were examined. The results indicated that RFV and MBR-CH exhibited significant correlations with renal and intestinal blood flows, with stronger correlations observed during blood removal. Additionally, ocular blood flow changes closely mirrored systemic dynamics, suggesting their potential as real-time indicators of shock progression and recovery. These findings indicate that ocular blood flow measurements may serve as real-time indicators of the systemic circulation status during hemorrhagic shock, offering potential insights into shock management and guiding tailored interventions. Thus, noninvasive ocular blood flow evaluation holds promise as an innovative tool for assessing systemic circulation dynamics during hemorrhagic shock.

The role of arterial stiffness in the onset of Takotsubo cardiomyopathy observed with noradrenaline administration and intracranial blood injection in rabbits

Takotsubo cardiomyopathy (TCM) has been reported to occur after subarachnoid hemorrhage, and the involvement of a critical activity of catecholamines has been mentioned, but the details of its onset have not been fully clarified. Recently, proper arterial stiffness could be measured with cardio-ankle vascular index. Therefore, we aimed to clarify the role of arterial stiffness in onset of TCM using rabbits under infusion of noradrenaline and injection of blood into brain ventricle. Rabbits were divided into three groups: infusion of noradrenaline (group A), infusion of noradrenaline + injection of saline into the brain ventricle (group B), infusion of noradrenaline + injection of blood in the brain ventricle (group C). Aortic arterial stiffness beta (_Aβ) and femoral arterial stiffness beta (_Fβ) were defined according to definition of the cardio-ankle vascular index. Blood pressure (BP), _Aβ, _Fβ, and femoral vessel resistance (FVR) were measured. Left ventricular movement were monitored with echocardiography. BP increased uniformly in all three groups. _Fβ in the group A, B and C increased from 3.6 ± 3.2, 3.6 ± 3.6 and 3.9_ ± 4.2 to 15 ± 2, 17.9 ± 2.4, 34.8 ± 9.1 due to the ICP enhancements in addition to noradrenaline administration, respectively. _Fβ in groups B and C was significantly larger than that in group A. On echocardiography, a much higher akinesic area of the apex was observed in group C compared with group A and B. Cardiac movements similar to TCM were observed slightly in group B and definitely in group C. Noradrenaline administration infusion and blood injection into the brain ventricle induced TCM accompanying with enhanced femoral arterial stiffness. These results suggested that elevated arterial stiffness might be involved in the formation of TCM in addition to a critical activity of catecholamines and an increase in intracranial pressure with blood injection.

Role of Rho Kinase in Regulating Arterial Stiffness in Anesthetized Rabbits

The effects of Rho kinase inhibitors fasudil and ripasudil on arterial stiffness were assessed using anesthetized rabbits, where the aortic β and femoral β were measured as a stiffness parameter at each arterial region. Intravenous administration of fasudil and ripasudil dose-dependently decreased blood pressure and femoral vascular resistance and increased femoral arterial blood flow, which appeared according to their in vitro potencies for Rho kinase inhibition. Both drugs increased the aortic β but decreased the femoral β at hypotensive doses. These results suggest that the inhibition of Rho kinase contributes to reducing elastic recoil in the aorta and an increase in compliance in the femoral artery. In addition, the Rho kinase-associated Ca2+-independent mechanism of arterial vascular smooth muscle contraction may be essential in the regulation of femoral arterial stiffness.

Differential Effects of Ca2+ Channel Blockers Nifedipine and Cilnidipine on Arterial Elasticity in the Aortic and Femoral Arterial Segments of Anesthetized Rabbits

Ca2+ channel blockers have potent vasodilatory effects and excellent efficacy in preserving organ blood flow. These hemodynamic actions may be partly controlled by the functional stiffness of conduit arteries. In this study, we assessed the effects of the L-type Ca2+ channel blocker nifedipine on aortic and femoral arterial stiffness (referred to as aortic β and femoral β, respectively) in anesthetized rabbits. To further clarify the involvement of the autonomic nervous system, we compared the effects of nifedipine with those of the L/N-type Ca2+ channel blocker cilnidipine. Further, the effect of the α-adrenergic receptor blocker doxazosin on the effects of nifedipine on arterial elasticity was examined. An antihypertensive dose of nifedipine (300 µg/kg, administered intravenously) was found to increase the aortic β but hardly affected the femoral β. An antihypertensive dose of cilnidipine (30 µg/kg, administered intravenously) increased the aortic β but decreased the femoral β. Interestingly, nifedipine decreased the femoral β in the presence of the α-adrenoceptor blocker doxazosin (1 mg/kg, administered intravenously). These effects suggest that L-type Ca2+ channel blockers essentially increase vascular elasticity via the decrement in arterial stiffness in the femoral artery segment, which is modified by the presence or absence of the inhibitory effect of each drug on reflex sympathetic nerve activity, while decreasing vascular elasticity via the increment in arterial stiffness in the aortic segment independently of sympathetic nerve activity.

Rapid Rise in Cardio-Ankle Vascular Index as a Predictor of Impending Cardiovascular Events -Smooth Muscle Cell Contraction Hypothesis for Plaque Rupture

Predictive factors for vascular events have not been established. The vasculature of the atheroma is supplied by penetration of the vasa vasorum through the smooth muscle cell layer from the adventitia. Smooth muscle cell contraction induces compression of the vasa vasorum, resulting in ischemia in intimal atheromatous lesions. Cardio-ankle vascular index (CAVI) has become known as an index of arterial stiffness of the arterial tree from the origin of the aorta to the ankle. CAVI reflects the progress of arteriosclerosis, and a rapid rise in CAVI indicates arterial smooth muscle cell contraction. We hypothesized that rapidly increased arterial stiffness evaluated by CAVI may be a predictor of impending cardiovascular events.

Assessment of Arterial Stiffness Using the Cardio-Ankle Vascular Index – What We Know and What We Strive for

Currently, the importance of assessing arterial stiffness as an integral indicator of cardiovascular risk, an indicator of arteriosclerosis, and a predictor of cardiovascular events has been demonstrated. The traditional indicator of arterial stiffness-pulse wave velocity-depends on the level of blood pressure, which makes it difficult to use it for dynamic assessment. The proposed new arterial stiffness index-the cardio-ankle vascular index (CAVI), does not depend on the level of blood pressure and is more convenient in practical use. CAVI has been widely used in clinical medicine for the past 15 years as an index for assessing cardiovascular diseases and risk factors, which has allowed for the expansion and deepening of research on this topic. This review focuses primarily on recent publications and new opportunities for evaluating vascular function using CAVI. The review provides information on solving methodological problems in evaluating CAVI, highlights the relationship between CAVI and future cardiovascular events, and provides cross-sectional data on the Association of CAVI with the presence of cardiovascular diseases and their risk factors. The results of studies on the effect of drug therapy and measures to control risk factors for cardiovascular diseases on CAVI are presented. While it remains unclear how much changes in CAVI over time can affect the forecast, research is currently being conducted in this direction. The use of CAVI also opens up new perspectives in the assessment of cardiovascular interactions, the study of vascular function in vasculitis and vascular injuries, as well as in geriatric medicine (concepts of premature vascular aging and excess vascular aging).

Real-Time Evaluation of Regional Arterial Stiffening, Resistance, and Ocular Circulation During Systemic Administration of Adrenaline in White Rabbits

Purpose

To evaluate continuous variations of ocular microcirculation by laser speckle flowgraphy and those of regional stiffening by pulse wave velocity (PWV) and vascular resistance under systemic adrenaline administration in rabbits.

Methods

Six 16-week-old male rabbits were evaluated. The mean blur rates in the retinal vessel (MBR-RV) and choroid (MBR-CH) were measured. We assessed blood pressure (BP), femoral and carotid vascular resistance, and the heart–ankle (ha)-PWV, heart–femoral (hf)-PWV, and femoral–ankle (fa)-PWV. Adrenaline (100, 300, and 1000 ng/kg) was intravenously administered over a 10-minute period during which the parameters were measured simultaneously every 2 minutes.

Results

The MBR-RV and MBR-CH values were dose-dependently increased by the adrenaline in parallel with increased BP. At the load of 100 ng/kg adrenaline, the ΔMBR-RV and ΔMBR-CH showed positive correlations with the variation rate in mean arterial blood pressure. Also, the variation rate in carotid vascular resistance and the Δfa-PWV and Δhf-PWV were significantly positively correlated with both the ΔMBR-RV and ΔMBR-CH. At the 300-ng/kg phase, the correlations between the Δha-PWV and both ΔMBR-RV and ΔMBR-CH were canceled; instead, the Δhf-PWV showed a significant negative correlation with the ΔMBR-RV and ΔMBR-CH. At the 1000-ng/kg phase, Δha-PWV again showed significant positive correlations with the ΔMBR-RV and ΔMBR-CH.

Conclusions

These results indicate the possibility that under a systemic administration of adrenaline in rabbits, not only the BP value but also the vascular resistance and arterial function are related to the variation in ocular microcirculation.

Translational Relevance

A real-time evaluation system of systemic regional arterial function and ocular microcirculation in rabbits was developed.

The influence of hemorrhagic shock on ocular microcirculation by obtained by laser speckle flowgraphy in a white rabbit model

PURPOSE

To clarify the continuous changes in the retinal vessels' and choroid's microcirculation during hemorrhagic shock and resuscitation in a rabbit model.

METHODS

Hemorrhagic shock by the removal of blood (30 mL) and resuscitation by a blood-return technique was induced in anesthetized male New Zealand White rabbits (n = 10). We evaluated the retinal vessel blood flow (relative flow volume: RFV) and choroidal blood flow (mean blur rate in the choroid area: MBR-CH) by laser speckle flowgraphy (LSFG), with simultaneous measurements of systemic hemodynamics and laboratory parameters.

RESULTS

RFV and MBR-CH showed significant decreases immediately after the initiation of blood removal and recovered by blood return. The lactate concentration tended to increase from baseline by the blood-removal operation, and it was significantly higher at the end of observation period. The %RFV and %MBR-CH each showed a significant positive correlation with mean arterial blood pressure, cardiac output, carotid blood flow, and central venous pressure. %RFV showed a significant positive correlation with %central venous oxygen saturation and negatively correlated with %lactate. The %hemoglobin did not show a significant correlation with %RFV or %MBR-CH.

CONCLUSION

This rabbit hemorrhagic shock model confirmed that ocular microcirculation measurements by LSFG feasibly reflect variations in systemic hemodynamics during hemorrhagic shock and recovery.

Cardio-Ankle Vascular Index in the Persons with Pre-Diabetes and Diabetes Mellitus in the Population Sample of the Russian Federation

The aim of this study was to evaluate Cardio-Ankle Vascular Index (CAVI) and increased arterial stiffness predictors in patients with carbohydrate metabolism disorders (CMD) in the population sample of Russian Federation. Methods: 1617 patients (age 25–64 years) were enrolled in an observational cross-sectional study Epidemiology of Cardiovascular Diseases and Their Risk Factors in the Regions of the Russian Federation (ESSE-RF). The standard ESSE-RF protocol has been extended to measure the cardio-ankle vascular index (CAVI), a marker of arterial stiffness. Patients were divided into three groups: patients with type 2 diabetes mellitus (n = 272), patients with prediabetes (n = 44), and persons without CMD (n = 1301). Results: Median CAVI was higher in diabetes and prediabetes groups compared with group without CMD (p = 0.009 and p < 0.001, respectively). Elevated CAVI (≥9.0) was detected in 16.8% of diabetes patients, in 15.9% of those with prediabetes, and in 9.0% of those without CMD (p < 0.001). The factors affecting on CAVI did not differ in CVD groups. In logistic regression the visceral obesity, increasing systolic blood pressure (SBP) and decreasing glomerular filtration rate (GFR) were associated with a pathological CAVI in CMD patients, and age, diastolic blood pressure (DBP), and cholesterol in persons without CMD. Conclusions: the CAVI index values in the prediabetes and diabetes patients were higher than in normoglycemic persons in a population sample of the Russian Federation. Since the identified disorders of arterial stiffness in prediabetes are similar to those in diabetes, their identification is important to prevent further cardiovascular complications.

[Cardio-ankle vascular index (CAVI) in diagnostics, risk and severity evaluation of magistral vessels lesion in patients with cardio-vascular diseases and type 2 diabetes]

Assesment of arterial stiffness the substantional prognostic factor for evaluating complications of cardiovascular diseases (CVD) in patients with atherosclerosis, hypertension and type 2 diabetes, may be performed using different parameters, including cardio-ankle vascular index (CAVI). The main purpose of this review is to analyze data from studies where CAVI is used to test the arterial wall stiffness in magistral vessels. CAVI measurement is non-invasive and performed by portable devices which makes it comfortable for ambulatory use in patients who come for a check-up and also in those who already are hospitalized. It does not require any special knowledge from investigator and the test lasts a couple of minutes long. CAVI does not depend on blood pressure changes and is more specific in structural changes of arterial wall assessment than brachial-ankle pulse wave velocity (baPWV). CAVI shows considerable correlation with markers of CVD like atherosclerotic plaques in vessels, diastolic disfunction of left ventricle and angina pectoris. CAVI may be used for early monitoring and assessing the lesions of target organs in patients with atherosclerosis, chronic hypertension and type 2 diabetes. Establishing CAVI as a standart parameter in assessing patients who are at risk of CVD can help to improve complications prevention, reduce mortality and prolong their lifespan.