Greater intima-media thickness in the carotid bulb is associated with reduced baroreflex sensitivity

Spontaneous baroreflex sensitivity is attenuated in male UCD-type 2 diabetes mellitus rats: A link between metabolic and autonomic dysfunction

Patients with type 2 diabetes mellitus (T2DM) have impaired arterial baroreflex function, which may be linked to the co-existence of obesity. However, the role of obesity and its related metabolic impairments on baroreflex dysfunction in T2DM is unknown. This study aimed to investigate the role of visceral fat and adiponectin, the most abundant cytokine produced by adipocytes, on baroreflex dysfunction in T2DM rats. Experiments were performed in adult male UCD-T2DM rats assigned to the following experimental groups (n = 6 in each): prediabetic (Pre), diabetes-onset (T0), 4 weeks after onset (T4), and 12 weeks after onset (T12). Age-matched healthy Sprague-Dawley rats were used as controls. Rats were anesthetized and blood pressure was directly measured on a beat-to-beat basis to assess spontaneous baroreflex sensitivity (BRS) using the sequence technique. Dual-energy X-ray absorptiometry (DEXA) was used to assess body composition. Data are presented as mean ± SD. BRS was significantly lower in T2DM rats compared with controls at T0 (T2D: 3.7 ± 3.2 ms/mmHg vs Healthy: 16.1 ± 8.4 ms/mmHg; P = 0.01), but not at T12 (T2D: 13.4 ± 8.1 ms/mmHg vs Healthy: 9.2 ± 6.0 ms/mmHg; P = 0.16). T2DM rats had higher visceral fat mass, adiponectin, and insulin concentrations compared with control rats (all P < 0.01). Changes in adiponectin and insulin concentrations over the measured time-points mirrored one another and were opposite those of the BRS in T2DM rats. These findings demonstrate that obesity-related metabolic impairments may contribute to an attenuated spontaneous BRS in T2DM, suggesting a link between metabolic and autonomic dysfunction.

Adverse childhood experiences are associated with altered cardiovascular reactivity to head-up tilt in young adults

Adverse childhood experiences (ACEs) are associated with greater prevalence of cardiovascular disease and altered acute stress reactivity. The current study investigated the effect of ACEs on hemodynamic and autonomic responses to orthostatic stress imposed by 60° head-up tilt (HUT) in young adults. Two-hundred twenty-six healthy young adults (age = 22.6 ± 1.5 yr; n = 116 females) without cardiovascular disease participated and had complete data. Participants underwent supine blood pressure (BP), R-R interval (RRI), cardiac output (CO), total peripheral resistance (TPR), and cardiovagal baroreflex sensitivity (cvBRS) testing followed by a transition to 60° HUT where measures were reassessed. Childhood adversity exposures were assessed based on categorical exposure and nonexposure to childhood household dysfunction and maltreatment, and <4 and ≥4 types of ACEs. Significantly greater increases in SBP (P < 0.05), DBP, MAP, and TPR (P < 0.01; all) following 60° HUT were observed in individuals with ≥4 compared with those with <4 types of ACEs. Attenuated decreases in RRI and cvBRS were observed in those with ≥4 types of ACEs (P < 0.05). Experiencing ≥4 types of ACEs was associated with augmented BP and TPR reactivity and a blunted decrease in cvBRS in response to 60° HUT in young adults. Results suggest that a reduced vagal response to orthostatic stress is present in those who have experienced ≥4 types of ACEs that may promote autonomic dysfunction. Future research examining the sympathetic and vagal baroreflex branches is warranted.

Heart Rate from Progressive Volitional Cycling Test Is Associated with Endothelial Dysfunction Outcomes in Hypertensive Chilean Adults

BACKGROUND

A progressive volitional cycling test is useful in determining exercise prescription in populations with cardiovascular and metabolic diseases. However, little is known about the association between heart rate during this test and endothelial dysfunction (EDys) parameters in hypertensive (HTN) patients.

OBJECTIVE

To investigate the association between EDys markers (flow-mediated dilation [FMD], pulse wave velocity of the brachial artery [PWVba], and carotid-intima media thickness [cIMT]) and heart rate during a cycling test in HTN adults. A secondary aim was to characterize cardiovascular, anthropometric, and body composition outcomes in this population.

METHODS

This was a descriptive clinical study in which adults (men and women) were assigned to one of three groups: HTN, elevated blood pressure (Ele), or a normotensive control group (CG), and completed a progressive cycling test. The primary outcomes were FMD, PWVba, cIMT, and heart rate (HR) at 25-50 watts (HR_25-50), 50-100 watts (HR_50-100), and 75-150 watts (HR_75-150) of the Astrand test. Secondary outcomes included body mass index (BMI), waist circumference, body fat percentage (BF%), skeletal muscle mass (SMM), resting metabolic rate (RMR), and estimated body age, as measured by a bio-impedance digital scale.

RESULTS

Analyses of the associations between FMD, PWV, and HR_25-50, HR_50-100, and HR_75-150 watts revealed no significant association in the HTN, Ele, and CG groups. However, a significant association was found between cIMT and HR_75-150 watts in the HTN group (R² 47.1, β -0.650, p = 0.038). There was also a significant trend (p = 0.047) towards increasing PWVba in the CG, Ele, and HTN groups.

CONCLUSION

Heart rate during a progressive cycling test is associated with the EDys parameters cIMT in HTN patients, with particularly strong predictive capacity for vascular parameters in the second and third stages of the Astrand exercise test compared to normotensive control.

High serum copeptin may be a marker of an increased carotid intima-media thickness in asymptomatic patients with type 1 diabetes

We aimed to study the association of copeptin with carotid intima-media thickness in 60 patients with type 1 diabetes (T1DM-patients). Our results suggest that copeptin might improve the stratification of cardiovascular risk in T1DM-patients. Further research is needed to determine the value in identifying carotid disease of this biochemical marker.

Natural History of Afferent Baroreflex Failure in Adults

OBJECTIVE

To describe the natural history of afferent baroreflex failure (ABF) based on systematic review of clinical and laboratory data in patients with a diagnosis of ABF at Mayo Clinic Rochester.

METHODS

We performed a retrospective chart review of all patients who underwent standardized autonomic reflex testing between 2000 and 2020 and had confirmation of the diagnosis of ABF by an autonomic disorders specialist. Patients were identified using a data repository of medical records. Variables included demographic, all-cause mortality, medications, ABF manifestations, comorbidities, and laboratory (autonomic testing, blood pressure monitoring, echocardiogram, brain imaging, plasma catecholamines, serum sodium level, and kidney function tests).

RESULTS

A total of 104 patients with ABF were identified. Head and neck radiation was the most common etiology (86.5%), followed by neck surgery (5.8%) and other causes (7.7%). The most common findings were hypertension (87.5%), fluctuating blood pressure (78.8%), orthostatic hypotension (91.3%), syncope (58.6%), headache (22.1%), and tachycardia (20.2%). Patients commonly received antihypertensives (66.3%), pressor agents (41.3%), or a combination of both (19.2%). The median latency from completion of radiation to ABF was longer compared to the latency in the surgery group (p < 0.0001). Comorbidities, including complications from neck radiation, were frequently seen and all-cause mortality was 39.4% over a 20-year period.

CONCLUSIONS

ABF should be suspected in patients with prior head and neck cancer treated by radiation or surgery who present with labile hypertension and orthostatic hypotension. Management may require both antihypertensive and pressor medications. The morbidity and mortality in ABF are high.

Seasonal Variations in the Achievement of Guideline Targets for HbA1c, Blood Pressure, and Cholesterol Among Patients With Type 2 Diabetes: A Nationwide Population-Based Study (ABC Study: JDDM49)

OBJECTIVE

Precise monthly achievement rates for reaching guideline targets for HbA_1c, blood pressure (BP), and lipid levels remain unknown. We evaluated achievement rates on a monthly basis in persons with type 2 diabetes mellitus (T2DM) and explored related factors.

RESEARCH DESIGN AND METHODS

This retrospective study initially analyzed data on 104,601 persons with T2DM throughout Japan. Patients whose HbA_1c, BP, and LDL cholesterol were measured ≥12 times during a 24-month period were included. We evaluated monthly achievement rates. Achieved targets were defined as HbA_1c <7%, BP <130/80 mmHg, and LDL cholesterol <100 mg/dL. Achievement of all targets was expressed as the "all ABC achievement."

RESULTS

A total of 4,678 patients were analyzed. The achievement rates of all ABC, HbA_1c, BP, and LDL cholesterol were lowest in winter, with those for systolic BP (SBP) being particularly low (all ABC, summer 15.6%, winter 9.6%; HbA_1c, 53.1%, 48.9%; SBP, 56.6%, 40.9%; LDL cholesterol, 50.8%, 47.2%). In winter, age ≥65 years (odds ratio 0.47 [95% CI 0.34-0.63]) was independently related to decreased achievement rates for SBP, BMI ≥25 kg/m² (BMI 25-30 kg/m², 0.45 [0.29-0.70]; BMI ≥30 kg/m², 0.35 [0.22-0.57]), and diabetes duration ≥10 years (0.53 [0.37-0.76]) were independently related to lower achievement rates for HbA_1c. Insulin use and sulfonylurea use were independently associated with the decreased all ABC achievement rates in both summer and winter.

CONCLUSIONS

The all ABC achievement rate for guideline targets changed on a monthly basis. Seasonal variations in the all ABC achievement rate should be considered when managing T2DM in ordinary clinical practices.

Clinical Implications of Baroreflex Sensitivity in Type 2 Diabetes

The evaluation of baroreflex sensitivity (BRS), which maintains systemic circulatory homeostasis, is an established tool to assess cardiovascular autonomic neuropathy in type 2 diabetes mellitus (T2DM). As BRS plays an important function in blood pressure regulation, reduced BRS leads to an increase in blood pressure variability, which further leads to reduced BRS. This sequence of events becomes a vicious cycle. The major risk factors for reduced BRS are T2DM and essential hypertension, but many other risk factors have been reported to influence BRS. In recent years, reports have indicated that glycemic variability (GV), such as short- and long-term GV that are considered important risk factors for macrovascular and microvascular complications, is involved in reductions in BRS independently of blood glucose levels. In this review, we discuss reduced BRS in T2DM, its features, and the potential for its reversal.

The additional impact of type 2 diabetes on baroreflex sensitivity of coronary artery disease patients might be undetectable in presence of deterioration of mechanical vascular properties

Both deterioration of the mechanical vascular properties of barosensitive vessels and autonomic derangement lead to modification of baroreflex sensitivity (BRS) in coronary artery disease (CAD) individuals. Type 2 diabetes (T2D) reduces BRS as well even in absence of cardiac autonomic neuropathy. The aim of the study is to clarify whether, assigned the degree of mechanical vascular impairment and without cardiac autonomic neuropathy, the additional autonomic dysfunction imposed in CAD patients by T2D (CAD-T2D) decreases BRS further. We considered CAD (n = 18) and CAD-T2D (n = 19) males featuring similar increases of average carotid intima media thickness (ACIMT) and we compared them to age- and gender-matched healthy (H, n = 19) subjects. BRS was computed from spontaneous beat-to-beat variability of heart period (HP) and systolic arterial pressure (SAP) at supine resting (REST) and during active standing (STAND). BRS was estimated via methods including time domain, spectral, cross-spectral, and model-based techniques. We found that (i) at REST BRS was lower in CAD and CAD-T2D groups than in H subjects but no difference was detected between CAD and CAD-T2D individuals; (ii) STAND induced an additional decrease of BRS visible in all the groups but again BRS estimates of CAD and CAD-T2D patients were alike; (iii) even though with different statistical power, BRS markers reached similar conclusions with the notable exception of the BRS computed via model-based approach that did not detect the BRS decrease during STAND. In presence of a mechanical vascular impairment, indexes estimating BRS from spontaneous HP and SAP fluctuations might be useless to detect the additional derangement of the autonomic control in CAD-T2D without cardiac autonomic neuropathy compared to CAD, thus limiting the applications of cardiovascular variability analysis to typify CAD-T2D individuals. Graphical abstract Graphical representation of the baroreflex sensitivity (BRS) estimated from spontaneous fluctuations of heart period and systolic arterial pressure via transfer function (TF) in low frequency (LF) band (from 0.04 to 0.15 Hz). BRS was reported as a function of the group (i.e., healthy (H), coronary artery disease (CAD) and CAD with type 2 diabetes (CAD-T2D) groups) at REST (black bars) and during STAND (white bars). Values are shown as mean plus standard deviation. The symbol "*" indicates a significant difference between conditions within the same group (i.e., H, CAD, or CAD-T2D) and the symbol "§" indicates a significant difference between groups within the same experimental condition (i.e., REST or STAND). BRS cannot distinguish CAD and CAD-T2D groups both at REST and during STAND, while it is useful to distinguish experimental conditions and separate pathological groups from H subjects.

Atherosclerosis of the carotid bulb is associated with the severity of orthostatic hypotension in non-diabetic adult patients: a cross-sectional study

BACKGROUND

The carotid bulb has a high density of baroreceptors that play an important role in maintaining blood pressure. We hypothesized that atherosclerosis of the carotid bulb would reflect the severity of orthostatic hypotension more accurately than would atherosclerosis of other carotid artery segments.

METHODS

This cross-sectional study included 198 non-diabetic adults. We measured the cardio-vascular ankle index as an index of arterial stiffness, intima-media thickness in each carotid artery segment (internal carotid artery, carotid bulb, distal and proximal portions, respectively, of the common carotid artery) as a measure of atherosclerosis, and heart rate variability as a measure of cardiac autonomic function. The sit-to-stand test was used to assess severity of orthostatic hypotension.

RESULTS

Intima-media thickness of the carotid bulb was correlated with orthostatic systolic blood pressure change (r = -0.218, p = 0.002), cardio-ankle vascular index (r = 0.365, p < 0.001) and heart rate variability parameters. Multivariate regression analysis revealed that among all of the segments, only intima-media thickness of the carotid bulb was an independent predictor of orthostatic systolic blood pressure change (p = 0.022).

CONCLUSION

Atherosclerosis of the carotid bulb was associated with severity of orthostatic hypotension, arterial stiffening and cardiac autonomic dysfunction than that of other carotid artery segments.

Glycemic variability in continuous glucose monitoring is inversely associated with baroreflex sensitivity in type 2 diabetes: a preliminary report

Background

It is presently unclear whether glycemic variability (GV) is associated with baroreflex sensitivity (BRS), which is an early indicator of cardiovascular autonomic neuropathy. The present study is the first to examine the relationships between BRS and GV measured using continuous glucose monitoring (CGM).

Methods

This was a multicenter, prospective, open-label clinical trial. A total of 102 patients with type 2 diabetes were consecutively recruited for this study. GV was assessed by measuring the standard deviation (SD), glucose coefficient of variation (CV), and the mean amplitude of glycemic excursions (MAGE) during CGM. The BRS was analyzed from electrocardiogram and blood pressure recordings using the sequence method on the first day of hospitalization.

Results

A total of 94 patients (mean diabetes duration 9.7 ± 9.6 years, mean HbA1c 61.0 ± 16.8 mmol/mol [7.7 ± 1.5%]) were analyzed. In the univariate analysis, CGM-SD (r = − 0.375, p = 0.000), CGM-CV (r = − 0.386, p = 0.000), and MAGE (r = − 0.395, p = 0.000) were inversely related to BRS. In addition to GV, the level of BRS correlated with the coefficient of variation in the R–R intervals (CVR-R) (r = 0.520, p = 0.000), heart rate (HR) (r = − 0.310, p = 0.002), cardio-ankle vascular index (CAVI) (r = − 0.326, p = 0.001), age (r = − 0.519, p = 0.000), and estimated glomerular filtration rate (eGFR) (r = 0.276, p = 0.007). Multiple regression analysis showed that CGM-CV and MAGE were significantly related to a decrease in BRS. These findings remained after adjusting the BRS for age, sex, hypertension, dyslipidemia, HR, eGFR, CAVI, and CGM-mean glucose. Additionally, BRS was divided according to quartiles of the duration of diabetes (Q1–4). BRS decreased after a 2-year duration of diabetes independently of age and sex.

Conclusions

GV was inversely related to BRS independently of blood glucose levels in type 2 diabetic patients. Measurement of BRS may have the potential to predict CV events in consideration of GV.

Trial registration UMIN Clinical Trials Registry UMIN000025964, 28/02/2017

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0683-2) contains supplementary material, which is available to authorized users.

Association between Carotid Intima Media Thickness and Heart Rate Variability in Adults at Increased Cardiovascular Risk

Background: Atherosclerotic carotid intima-media thickness (IMT) may be associated with alterations in the sensitivity of carotid baroreceptors. The aim of this study was to investigate the association between carotid IMT and the autonomic modulation of heart rate variability (HRV). Methods: A total of 101 subjects were enrolled in this prospective observational study. The carotid IMT was determined by duplex ultrasonography. The cardiac autonomic function was determined through HRV measures during the Deep Breathing Test. Linear regression models, adjusted for demographics, comorbidities, body mass index, waist-hip-ratio, and left ventricular ejection fraction were used to evaluate the association between HRV parameters and carotid IMT. Results: Participants had a mean age of 60.4 ± 13.4 years and an estimated 10-year atherosclerotic cardiovascular disease (ASCVD) risk score (using the Pooled Cohort Equations) of 16.4 ± 17. The mean carotid media thickness was highest (0.90 ± 0.19 mm) in the first quartile of the standard deviation of all RR intervals (SDNN) (19.7 ± 5.1 ms) and progressively declined in each subsequent quartile to 0.82 ± 0.21 mm, 0.81 ± 0.16 mm, and 0.68 ± 0.19 in quartiles 2 (36.5 ± 5.9 ms), 3 (57.7 ± 6.2 ms) and 4 (100.9 ± 22.2 ms), respectively. In multivariable adjusted models, there was a statistical significant association between SDNN and carotid IMT (OR -0.002; 95%CI -0.003 to -0.001, p = 0.005). The same significant association was found between carotid IMT and other measures of HRV, including coefficient of variation of RR intervals (CV) and dispersion of points along the line of identity (SD2). Conclusions: In a cohort of individuals at increased cardiovascular risk, carotid IMT as a marker of subclinical atherosclerosis was associated with alterations of HRV indicating an impaired cardiac autonomic control, independently of other cardiovascular risk factors.

Post-Carotid Endarterectomy Hypertension. Part 1: Association with Pre-operative Clinical, Imaging, and Physiological Parameters

OBJECTIVE/BACKGROUND

Post-endarterectomy hypertension (PEH) is a well recognised, but poorly understood, phenomenon after carotid endarterectomy (CEA) that is associated with post-operative intracranial haemorrhage, hyperperfusion syndrome, and cardiac complications. The aim of the current study was to identify pre-operative clinical, imaging, and physiological parameters associated with PEH.

METHODS

In total, 106 CEA patients undergoing CEA under general anaesthesia underwent pre-operative evaluation of 24 hour ambulatory arterial blood pressure (BP), baroreceptor sensitivity, cerebral autoregulation, and transcranial Doppler measurement of cerebral blood flow velocity (CBFv) and pulsatility index. Patients who met pre-existing criteria for treating PEH after CEA (systolic BP [SBP] > 170 mmHg without symptoms or SBP > 160 mmHg with headache/seizure/neurological deficit) were treated according to a previously established protocol.

RESULTS

In total, 40/106 patients (38%) required treatment for PEH at some stage following CEA (26 in theatre recovery [25%], 27 while on the vascular surgical ward [25%]), while seven (7%) had SBP surges > 200 mmHg back on the ward. Patients requiring treatment for PEH had a significantly higher pre-operative SBP (144 ± 11 mmHg vs. 135 ± 13 mmHg; p < .001) and evidence of pre-existing impairment of baroreceptor sensitivity (3.4 ± 1.7 ms/mmHg vs. 5.3 ± 2.8 ms/mmHg; p = .02). However, PEH was not associated with any other pre-operative clinical features, CBFv, or impaired cerebral haemodynamics. Paradoxically, autoregulation was better preserved in patients with PEH. All four cases of hyperperfusion associated symptoms were preceded by PEH. Length of hospital stay was significantly increased in patients with PEH (p < .001).

CONCLUSION

In this study, where all patients underwent CEA under general anaesthesia, PEH was associated with poorly controlled pre-operative BP and impaired baroreceptor sensitivity, but not with other peripheral or central haemodynamic parameters, including impaired cerebral autoregulation.

Baroreflex Sensitivity in Children and Adolescents: Physiology, Hypertension, Obesity, Diabetes Mellitus

The increased prevalence of obesity in children and its complications have led to a greater interest in studying baroreflex sensitivity (BRS) in children. This review of BRS in children and adolescents includes subtopics on: 1. Resting values of BRS and their reproducibility, 2. Genetics of BRS, 3. The role of a primarily low BRS and obesity in the development of hypertension, and 4. Association of diabetes mellitus, BRS, and obesity. The conclusions specific to this age follow from this review: 1. The mean heart rate (HR) influences the measurement of BRS. Since the mean HR decreases during adolescence, HR should be taken into account. 2. A genetic dependency of BRS was found. 3. Low BRS values may precede pathological blood-pressure elevation in children with white-coat hypertension. We hypothesize that low BRS plays an active role in the emergence of hypertension in youth. A contribution of obesity to the development of hypertension was also found. We hypothesize that both factors, a primarily low BRS and obesity, are partially independent risk factors for hypertension in youths. 4. In diabetics, a low BRS compared to healthy children can be associated with insulin resistance. A reversibility of the BRS values could be possible after weight loss.

Association between Birth Characteristics and Cardiovascular Autonomic Function at Mid-Life

Background

Low birth weight is associated with an increased risk of cardiovascular diseases in adulthood. As abnormal cardiac autonomic function is a common feature in cardiovascular diseases, we tested the hypothesis that low birth weight may also be associated with poorer cardiac autonomic function in middle-aged subjects.

Methods

At the age of 46, the subjects of the Northern Finland Birth Cohort 1966 were invited to examinations including questionnaires about health status and life style and measurement of vagally-mediated heart rate variability (rMSSD) from R-R intervals (RRi) and spontaneous baroreflex sensitivity (BRS) in both seated and standing positions. Maternal parameters had been collected in 1965–1966 since the 16^th gestational week and birth variables immediately after delivery. For rMSSD, 1,799 men and 2,279 women without cardiorespiratory diseases and diabetes were included and 902 men and 1,020 women for BRS. The analyses were adjusted for maternal (age, anthropometry, socioeconomics, parity, gestational smoking) and adult variables (life style, anthropometry, blood pressure, glycemic and lipid status) potentially confounding the relationship between birth weight and autonomic function.

Results

In men, birth weight correlated negatively with seated (r = -0.058, p = 0.014) and standing rMSSD (r = -0.090, p<0.001), as well as with standing BRS (r = -0.092, p = 0.006). These observations were verified using relevant birth weight categories (<2,500 g; 2,500–3,999 g; ≥4,000 g). In women, birth weight was positively correlated with seated BRS (r = 0.081, p = 0.010), but none of the other measures of cardiovascular autonomic function. These correlations remained significant after adjustment for potential confounders (p<0.05 for all).

Conclusions

In men, higher birth weight was independently associated with poorer cardiac autonomic function at mid-life. Same association was not observed in women. Our findings suggest that higher, not lower, birth weight in males may contribute to less favourable cardiovascular autonomic regulation and potentially to an elevated cardiovascular risk in later life.

Short and Long-Term Effect of Carotid Artery Stenting on Arterial Blood Pressure Measured through Ambulatory Blood Pressure Monitoring

BACKGROUND

The aim of this study was to assess the short and long-term effects of carotid artery stenting (CAS) procedure on blood pressure (BP) through ambulatory BP monitoring.

METHODS

One hundred fifty three patients who underwent CAS for primary or secondary protection from December 2010 to September 2013 were enrolled to our study. The BP levels of total of 123 patients were monitored for 1 year. Thereafter, the pre-procedure levels of BP were compared with BP levels at the 24-hour and the first year intervals after the procedure.

RESULTS

Systolic and diastolic BP levels at the 24-hour and the first year intervals after CAS were significantly lower than the pre-procedure BP levels. The mean 24-hour systolic BP was 113 ± 13 mmHg and diastolic BP was 63 ± 8 mmHg, both of which were significantly lower (p < 0.001 and p < 0.001 respectively), while the pre-procedure mean systolic BP was 133 ± 10 mmHg and the mean diastolic BP was 75 ± 9 mmHg. Moreover, the mean first-year systolic BP was 125 ± 10 mmHg with a decline of 8 ± 8 mmHg and mean diastolic BP was 71 ± 8 mmHg with a decline of 4 ± 7 mmHg, both of which were again significantly lower compared to the pre-procedure levels (p < 0.001 and p < 0.001 respectively).

CONCLUSIONS

The results of our study suggested that systolic and diastolic BP levels diminished after CAS. Additionally, BP reduction continued even 1 year after the CAS.

Cardiovagal and adrenergic function tests in unilateral carotid artery stenosis patients-a Valsalva manoeuvre tool to show an autonomic dysfunction?

BACKGROUND

The stability of an arterial baroreflex depends also upon the integrity of the afferent limb. For its quantification, we can use a noninvasive test such as baroreceptor sensitivity estimation during Valsalva manoeuvre. The aim of this study was to evaluate potential autonomic dysfunction in patients with unilateral severe carotid disease and compare the results to the results obtained from an age and gender matched group of healthy volunteers.

METHODS

We evaluated dynamic changes during Valsalva manoeuvre (Valsalva ratio, cardiovagal and adrenergic baroreceptor sensitivity, sympathetic indexes and its dynamic ranges) in 41 patients (29 males; 62.9 ± 7.4 years) and compared the results to results obtained from volunteers (62.8 ± 7.0 years).

RESULTS

Valsalva ratio between the patients and control group revealed no significant difference, as well as cardiovagal and adrenergic baroreceptor sensitivity. Sympathetic indexes, except for sympathetic index 2, reflecting the sympathetic vasoconstrictor baroreceptor response in late phase 2 of Valsalva manoeuvre (7.1 ± 13.1 mmHg in patients vs. 11.4 ± 10.2 mmHg in control group; p = 0.012) showed no significant differences between the studied groups. The most prominent dynamic range between the groups was within the sympathetic index 2.

CONCLUSION

With some Valsalva manoeuvre test results, we were not able to show severe autonomic dysfunction in unilateral severe carotid stenosis patients except for lower vasoconstriction response within the late phase 2 of the manoeuvre.

Simple cardiovagal and adrenergic function tests in carotid artery stenosis patients as a potential tool for determining a transient autonomic dysfunction

PURPOSE

The arterial baroreflex depends on the integrity of the afferent limb, which can be quantified using the baroreceptor's sensitivity (BRS) during the Valsalva maneuver (VM). The aim of this study was to evaluate, using autonomic nervous system tests, the autonomic function in patients after a carotid artery angioplasty (CAS).

METHODS

We evaluated the changes in blood pressure (BP) during the VM (Valsalva ratio, BRS, sympathetic indexes) in 41 patients with symptomatic, unilateral, internal carotid artery stenosis.

RESULTS

The Valsalva ratio between the baseline and the post-procedural day (1.3 ± 0.1 vs 1.44 ± 0.3; P = 0.002) and the post-procedural day and a month later (1.44 ± 0.3 vs 1.3 ± 0.3; P = 0.0002) revealed significant differences. This was confirmed with a cardiovagal BRS test. However, the adrenergic BRS did not reveal any differences. Sympathetic indexes [BP fall (SI1) and recovery during phase 2 (SI2)] showed differences for the periods before and a day after the treatment (36.9 ± 18.0 vs 27.2 ± 21.4 and 7.1 ± 13.1 vs 3.0 ± 8.2, respectively; P = 0.004) and for SI1 a day and a month after the treatment (27.2 ± 21.4 vs 37.1 ± 21.8; P = 0.036). The dynamic ranges between S1 and S3 (the difference in the BP between the baseline and the end of phase 2) were also different (P = 0.007 and P = 0.044, respectively).

CONCLUSION

We found heterogeneous responses in the BP regulation obtained with the Valsalva maneuver in our patients; however, we could not confirm that CAS provoked any long-term autonomic dysfunction, except for 1 day after the procedure.

Postprandial hypotension as a risk marker for asymptomatic lacunar infarction

OBJECTIVE

Increasing blood pressure (BP) variability is reported to be a cardiovascular risk factor. However, the clinical implications of postprandial hypotension (PHYPO), a commonly observed BP variability in elderly persons, are poorly understood. Here, we investigated the possible associations between postprandial BP decline and asymptomatic cerebral damage in community residents.

METHODS

Study participants consisted of 1308 general community residents (65 ± 9 years old). Postprandial BP change was calculated from SBP measured just before and 30 min after lunch. PHYPO was defined as a decline in SBP of more than 20 mmHg. The presence of asymptomatic cerebrovascular damage was evaluated by brain MRI.

RESULTS

Prevalence of lacunar infarction was significantly higher in participants with PHYPO (P = 0.004). A postprandial decline in SBP was linearly increased with the number of lacunar lesions (none, n = 1200, -3.4± 11.3 mmHg; one lesion, n = 82, -5.2 ± 11.8; two lesions, n = 18, -6.9 ± 11.5; three lesions, n = 7, -13.4 ± 11.3; and four lesions, n = 1, -27; P = 0.012). Although participants with PHYPO were older (P < 0.001) and had higher preprandial BP (P < 0.001) and faster pulse wave velocity (P = 0.001), multivariate analysis adjusted for these covariates indicated that postprandial BP decline was an independent determinant for the number of lacunar infarctions (P = 0.004). No significant associations were observed with grade of periventricular hyperintensity or frequency of microbleeds. These relationships were also found in an analysis based on central BP, whereas no superiority was seen in the analysis based on central BP.

CONCLUSION

Postprandial BP decline is an overlooked risk marker for asymptomatic lacunar infarction in community residents.

Maximum home systolic blood pressure is a useful indicator of arterial stiffness in patients with type 2 diabetes mellitus: post hoc analysis of a cross-sectional multicenter study

AIMS

Maximum (max) home systolic blood pressure (HSBP) as well as mean HSBP or HSBP variability was reported to increase the predictive value of target organ damage. Yet, the association between max HSBP and target organ damage in patients with type 2 diabetes has never been reported. The aim of this study was to investigate the association between max HSBP and pulse wave velocity (PWV), a marker of arterial stiffness which in turn is a marker of target organ damage, in patients with type 2 diabetes.

METHODS

We assessed the relationship of mean HSBP or max HSBP to PWV, and compared area under the receiver-operating characteristic curve (AUC) of mean HSBP or max HSBP for arterial stiffness in 758 patients with type 2 diabetes.

RESULTS

In the univariate analyses, age, duration of diabetes mellitus, body mass index, mean clinic systolic blood pressure (SBP), mean HSBP and max HSBP were associated with PWV. Multivariate linear regression analyses indicated that mean morning SBP (β=0.156, P=0.001) or max morning SBP (β=0.146, P=0.001) were significantly associated with PWV. AUC (95% CI) for arterial stiffness, defined as PWV equal to or more than 1800 cm per second, in mean morning SBP and max morning SBP were 0.622 (0.582-0.662; P<0.001) and 0.631 (0.591-0.670; P<0.001), respectively.

CONCLUSIONS

Our findings implicate that max HSBP as well as mean HSBP was significantly associated with arterial stiffness in patients with type 2 diabetes.

From the First Spectral Analysis of Blood Pressure Variability in the World to the Present Time: Contribution of the Department of Physiology of the Faculty of Medicine, Masaryk University, Brno

The review shows the significance of blood pressure regulation studies conducted during several decades at the Department of Physiology, Faculty of Medicine, Masaryk University, Brno. Continuous non-invasive blood pressure measurement was first introduced and patented here and, with the obtained data, the first spectral analysis of blood pressure was performed. This method was used in many different physiological studies on the relationship of blood pressure regulation to circulatory parameters, breathing, and baroreflex sensitivity. The article deals with studies on risk stratification of sudden cardiac death according to decreased baroreflex sensitivity, 24-hour heart rate variability, the amount of extrasystoles and late potentials. Importance of the new method of determination of one summation risk index is described here. A summary of the new conception of the relationship between low baroreflex sensitivity and hypertension is presented. Here, not only pathological changes of the vessel wall but also increased sympathetic activity and genetic predisposition play a role. Importance of studies conducted in young adults is highlighted, as inherited BRS decrease contributes to earlier blood pressure increase in the young. This research is highly topical, since prevention of hypertension in childhood is possible. Recent studies are dedicated to blood pressure regulation in young diabetics.

Favorable effects of carotid endarterectomy on baroreflex sensitivity and cardiovascular neural modulation: a 4-month follow-up

Carotid surgery variably modifies carotid afferent innervation, thus affecting arterial baroreceptor sensitivity. Low arterial baroreflex sensitivity is a well-known independent risk factor for cardiovascular diseases. The aim of this study was to assess the 4-mo effects of carotid endarterectomy (CEA) on arterial baroreceptor sensitivity and cardiovascular autonomic profile in patients with unilateral carotid stenosis. We enrolled 20 patients (72 ± 8 yr) with unilateral >70% carotid stenosis. ECG, beat-by-beat blood pressure, and respiration were continuously recorded before and 126 ± 9 days after CEA, at rest and during a 75° head-up tilt. Both pharmacological (modified Oxford technique, BRS) and spontaneous (index α, spectral analysis) arterial baroreflex sensitivity were assessed. Cardiovascular autonomic profile was evaluated by plasma catecholamines and spectral indexes of cardiac sympathovagal modulation [low-frequency R-R interval (LFRR), low frequency-to high frequency ratio (LF/HF), high-frequency R-R interval (HFRR)] and sympathetic vasomotor control [low-frequency systolic arterial pressure (LFSAP)] obtained from heart rate and SAP variability. After CEA, both the index α and BRS were higher (P < 0.02) at rest. SAP variance decreased both at rest and during tilt (P < 0.02). Before surgery, tilt did not modify the autonomic profile compared with baseline. After CEA, tilt increased LF/HF and LFSAP and reduced HFRR compared with rest (P < 0.02). Four months after CEA was performed, arterial baroreflex sensitivity was enhanced. Accordingly, the patients' autonomic profile had shifted toward reduced cardiac and vascular sympathetic activation and enhanced cardiac vagal activity. The capability to increase cardiovascular sympathetic activation in response to orthostasis was restored. Baroreceptor sensitivity improvement might play an additional role in the more favorable outcome observed in patients after carotid surgery.

Maximum value of home blood pressure: a novel indicator of target organ damage in hypertension

The maximum office systolic blood pressure (SBP) has been shown to be a strong predictor of cardiovascular events, independently of the mean SBP level. However, the clinical implications of maximum home SBP have never been reported. We investigated the association between the maximum home SBP and target organ damage (TOD). We assessed the left ventricular mass index (LVMI) and carotid intima-media thickness (IMT) using ultrasonography and the urinary albumin/creatinine ratio (UACR) as measures of TOD in 356 never-treated hypertensive subjects. Home BP was taken in triplicate in the morning and evening, respectively, for 14 consecutive days with a memory-equipped device. The maximum home SBP was defined as the maximum mean triplicate BP reading in the 14-day period for each individual and was significantly correlated with LVMI (r=0.51, P<0.001), carotid IMT (r=0.40, P<0.001), and UACR (r=0.29, P<0.001). The correlation coefficients with LVMI and carotid IMT were significantly larger for the maximum home SBP than the mean home SBP. In multivariate regression analyses, the maximum home SBP was independently associated with LVMI and carotid IMT, regardless of the mean home BP level. In the prediction of left ventricular hypertrophy and carotid atherosclerosis, the goodness-of-fit of the model was significantly improved when the maximum home SBP was added to the sum of the mean office and home BPs (P=0.002 and P<0.001, respectively). These findings indicate that assessment of the maximum home SBP, in addition to the mean home SBP, might increase the predictive value of hypertensive TOD in the heart and artery.

Ventilatory chaos is impaired in carotid atherosclerosis

Ventilatory chaos is strongly linked to the activity of central pattern generators, alone or influenced by respiratory or cardiovascular afferents. We hypothesized that carotid atherosclerosis should alter ventilatory chaos through baroreflex and autonomic nervous system dysfunctions. Chaotic dynamics of inspiratory flow was prospectively evaluated in 75 subjects undergoing carotid ultrasonography: 27 with severe carotid stenosis (>70%), 23 with moderate stenosis (<70%), and 25 controls. Chaos was characterized by the noise titration method, the correlation dimension and the largest Lyapunov exponent. Baroreflex sensitivity was estimated in the frequency domain. In the control group, 92% of the time series exhibit nonlinear deterministic chaos with positive noise limit, whereas only 68% had a positive noise limit value in the stenoses groups. Ventilatory chaos was impaired in the groups with carotid stenoses, with significant parallel decrease in the noise limit value, correlation dimension and largest Lyapunov exponent, as compared to controls. In multiple regression models, the percentage of carotid stenosis was the best in predicting the correlation dimension (p<0.001, adjusted R(2): 0.35) and largest Lyapunov exponent (p<0.001, adjusted R(2): 0.6). Baroreflex sensitivity also predicted the correlation dimension values (p = 0.05), and the LLE (p = 0.08). Plaque removal after carotid surgery reversed the loss of ventilatory complexity. To conclude, ventilatory chaos is impaired in carotid atherosclerosis. These findings depend on the severity of the stenosis, its localization, plaque surface and morphology features, and is independently associated with baroreflex sensitivity reduction. These findings should help to understand the determinants of ventilatory complexity and breathing control in pathological conditions.

Association between depression and intima-media thickness of carotid bulb in asymptomatic young adults

OBJECTIVE

Although there is growing evidence that symptoms of depression influence the development of coronary artery disease, information on the underlying subclinical atherosclerotic process is scant in young adults. The study examined the association between symptoms of depression and subclinical atherosclerosis, determined by carotid intima-media thickness in asymptomatic young individuals.

METHODS

A cross-sectional study was performed in Bogalusa, Louisiana, a semi-rural biracial (black-white) community. A sample of 996 individuals aged 24 to 44 years (71% were white and 43% were male) enrolled in the Bogalusa Heart Study. The variables included symptoms of depression measured by the Center for Epidemiological Studies-Depression Scale; intima-media thickness of different segments of carotid artery by B-mode ultrasonography; measures of adiposity and glucose homeostasis, lipoproteins, and blood pressure; and cigarette smoking status.

RESULTS

Both the adjusted and the unadjusted associations between depression score and carotid bulb intima-media thickness were significant, whereas similar associations with internal carotid and common carotid thickness were nonsignificant. In the multivariable regression model, after adjusting for all covariates, a positive effect of depression scores (Center for Epidemiological Studies-Depression score) and a negative effect of interaction between depression score ratio of total cholesterol (TC)/high-density lipoprotein (HDL) were significant. In a subgroup analysis (among individuals with a ratio of TC/HDL < or = 5) a positive effect of depression on carotid bulb intima-media thickness was significant, whereas the interaction between depression and ratio of TC/HDL was nonsignificant. In subsequent analysis, if individuals with a higher ratio of TC/HDL were included, both depression and negative interaction term were significant.

CONCLUSION

The observations show the detrimental effect of depression on subclinical vascular changes in asymptomatic young individuals. The findings underscore the need for considering depression in risk factor profiling. Further study is recommended to investigate the basis of a lower carotid bulb intima-media thickness among subjects with a high depression score and a high ratio of TC/HDL.

A review of neuroimaging studies of stressor-evoked blood pressure reactivity: emerging evidence for a brain-body pathway to coronary heart disease risk

An individual's tendency to show exaggerated or otherwise dysregulated cardiovascular reactions to acute stressors has long been associated with increased risk for clinical and preclinical endpoints of coronary heart disease (CHD). However, the 'brain-body' pathways that link stressor-evoked cardiovascular reactions to CHD risk remain uncertain. This review summarizes emerging neuroimaging research indicating that individual differences in stressor-evoked blood pressure reactivity (a particular form of cardiovascular reactivity) are associated with activation patterns in corticolimbic brain areas that are jointly involved in processing stressors and regulating the cardiovascular system. As supported empirically by activation likelihood estimates derived from a meta-analysis, these corticolimbic areas include divisions of the cingulate cortex, insula, and amygdala--as well as networked cortical and subcortical areas involved in mobilizing hemodynamic and metabolic support for stress-related behavioral responding. Contextually, the research reviewed here illustrates how behavioral medicine and health neuroscience methods can be integrated to help characterize the 'brain-body' pathways that mechanistically link stressful experiences with CHD risk.

Impaired Baroreceptor Reflex Sensitivity in Acute Stroke Is Associated With Insular Involvement, But Not With Carotid Atherosclerosis

Background and Purpose— Impaired baroreflex sensitivity (BRS) has been previously shown to be of prognostic value in patients with cardiovascular disease and stroke. Because baroreflex seems to be blunted by both carotid atherosclerosis and by lesions affecting central processing, controversy exists regarding the etiology of stroke-related baroreflex changes. The insula may play a central role in baroreflex modulation. The aim of the study was therefore to examine BRS in patients with acute stroke with regard to carotid atherosclerosis and insular involvement.

Methods— We evaluated spontaneous BRS in 96 patients with acute stroke within 72 hours of ictus and 41 control subjects using a sequential crosscorrelation method.

Results— Fifty-two patients with ischemic stroke and 44 patients with intracerebral hemorrhage, mean age 58.4 years, were included. With comparable carotid atherosclerosis profiles, patients with stroke had significantly lower BRS than control subjects (3.3 versus 5.3, P <0.001). Carotid atherosclerosis had no influence on variance of the BRS values in the acute stroke group. Patients with insular involvement had significantly lower BRS than patients with no insular involvement (2.55 versus 4.35, P =0.001) or control subjects (2.55 versus 5.3, P <0.001). Furthermore, patients with left insular involvement had significantly lower BRS than patients with right insular involvement (2.3 versus 3.5, P =0.049). There was no significant difference between patients with no insular lesions and control subjects ( P =0.263).

Conclusions— We demonstrated that baroreflex impairment in acute stroke is not associated with carotid atherosclerosis but with insular involvement. Both insulae seem to participate in processing the baroreceptor information with the left insula being more dominant.

A hyperlipidemic rabbit model provides new insights into pulmonary zinc exposure effects on cardiovascular health

This study ascertains the effects of zinc, a major component of particulate matter, on pulmonary and systemic endpoints using hyperlipidemic rabbits to model diet-induced human atherosclerosis. New Zealand White rabbits were fed a normal or cholesterol-enriched diet and then were intratracheally instilled 1x/week for 4 weeks with saline or 16 microg/kg of zinc, equal parts sulfate and oxide. Physiologic responses, blood after each exposure, and terminal bronchoalveolar lavage (BAL) were assessed. Rabbits fed a cholesterol-rich diet developed hyperlipidemia and had consistently higher circulating leukocyte counts than rabbits fed normal chow. Within minutes after zinc instillation, saturation of peripheral oxygen was decreased in hyperlipidemic rabbits and heart rate was increased in hyperlipidemic rabbits with total serum cholesterol levels greater than 200 mg/dl. Total circulating leukocytes levels were increased 24 h after the first zinc instillation, but upon repeated exposures this effect was attenuated. After repeated zinc exposures, BAL fluid (BALF) N-acetylglucosaminidase activity was increased regardless of hyperlipidemic state. Hyperlipidemic rabbits had an increase in BALF-oxidized glutathione and a decrease in serum nitrite. The study elucidates mechanisms by which the zinc metal component of PM drives cardiovascular health effects, as well as the possible susceptibility induced by hyperlipidemia. Furthermore, the study exemplifies the benefits of monitoring circulatory physiology during exposure as well as after exposure.

The autonomic nervous system and ischemic stroke: a reciprocal interdependence

Signs and symptoms of autonomic nervous system (ANS) dysfunction are frequently reported after ischemic or haemorrhagic stroke and in many cases they exhibit peculiar patterns in relationship with the site and the extension of brain lesion. However if an ANS disorder can cause or predispose to a stroke is far from being correctly known. Evidences in favor of a pathogenetic mechanism of an ANS dysfunction are reported for myocardial infarction and such data are likely to be appropriate also for atherothrombotic type of ischemic stroke. On the other hand, it is well known that many risk factors for this pathology are strongly correlated with an altered functioning of ANS so that a reciprocal interdependence between ANS and stroke can be hypothesized. This review points to evidence the possible relationship existing between these two conditions and suggests a quite different diagnostic and therapeutic approach to both on the basis of their pathogenetic mechanisms.

Percutaneous injection of lidocaine within the carotid body area in carotid artery stenting: an "old-new" technique

Severe bradycardia is a common untoward effect during balloon angioplasty when performing carotid artery stenting. Therefore atropine injection even before dilatation and the presence of an anesthesiologist are advocated in all patients. In the surgical literature, injection of a local anesthetic agent into the carotid sinus before carotid endarterectomy was performed in an attempt to ameliorate perioperative hemodynamic instability. This study was undertaken to test the hypothesis that percutaneous infiltration of the carotid sinus with local anesthetic immediately before balloon dilatation reduces bradycardia and ameliorates the need for atropine injection or the presence of an anesthesiologist. Infiltration of the carotid sinus with 5 ml of 1% lidocaine, 3 min before dilatation, was performed in 30 consecutive patients. No one exhibited any significant rhythm change that required atropine injection. The anesthesiologist did not face any hemodynamic instability during the carotid artery stenting procedure.

Reduced low-frequency heart rate variability relates to greater intimal-medial thickness of the carotid wall in two samples

INTRODUCTION

We investigated the relationship between heart rate variability and preclinical carotid intima-media thickening, a putative index of atherosclerosis.

METHODS

A sample of 350 men and women (mean age 56.8 years) selected for the presence or absence of untreated hypertension was assessed for heart rate variability at rest and separately for carotid intima-media thickness using duplex ultrasonography (Pittsburgh study). Findings from this sample were cross-validated in a subsample of 68 men drawn from the Kuopio Ischemic Heart Disease Risk Factor trial and selected for the presence or absence of angina.

RESULTS

In both samples, regression analyses, controlling for known risk factors, showed a significant negative relationship between mean carotid intima-media thickness and low-frequency (0.05-0.15 Hz) heart rate variability, but not high-frequency variability.

DISCUSSION

The mechanism underlying this relationship remains unclear. The absence of difference in high-frequency variation questions any interpretation in terms of vagal function; the difference in low-frequency variation may implicate vessel wall characteristics or decreased sympathetic nervous system influence.

CONCLUSION

Decreased amplitude of low-frequency heart rate variability seems associated with a preclinical atherosclerotic index.

Arterial stiffness, cardiovagal baroreflex sensitivity and postural blood pressure changes in older adults: the Rotterdam Study

OBJECTIVE

Arterial stiffness may be involved in the impairment of the arterial baroreflex. In the present study the associations between arterial stiffness and cardiovagal baroreflex sensitivity (BRS) and between BRS and postural blood pressure (BP) changes were investigated within the framework of the Rotterdam Study.

METHODS

Arterial stiffness was determined by aortic pulse wave velocity and the carotid distensibility coefficient. Continuous recording of the R-R interval and finger BP was performed with the subject resting supine, and BRS was estimated from the spontaneous changes in systolic BP and corresponding interbeat intervals. Measures of aortic stiffness or carotid distensibility and BRS were available in 2490 and 2083 subjects, respectively. The association between arterial stiffness and ln BRS was investigated by multivariate linear regression analysis and then by analysis of covariance, comparing BRS by quartiles of arterial stiffness.

RESULTS

The mean age of the subjects was 71.7 +/- 6.6 (41.7% men). Aortic stiffness was negatively associated [beta = -0.029; 95% confidence interval (CI): -0.040, -0.019] and the carotid distensibility coefficient positively associated with BRS (beta = 0.017; 95% CI: 0.010, 0.024). An orthostatic decrease in systolic BP was absent in 1609 subjects, between 1 and 10 mmHg in 502 and >10 mmHg in 269 subjects, with corresponding mean values (95% CI) of ln BRS of 1.47 (1.44-1.51), 1.43 (1.37-1.49) and 1.36 (1.28-1.44) ms/mmHg (test for trend P < 0.019). An orthostatic decrease in diastolic BP was absent in 1123 subjects, 1-10 mmHg in 1057 and >10 mmHg in 209 subjects, with corresponding mean values of ln BRS of 1.49 (1.45-1.53), 1.41 (1.37-1.45) and 1.45 (1.36-1.54) ms/mmHg (P < 0.04).

CONCLUSION

In a large population of older subjects, arterial stiffness appears to be an independent determinant of impaired BRS. Within the same population, impaired BRS was associated with orthostatic BP changes.

Effects of birth weight on spontaneous baroreflex sensitivity in adult life

BACKGROUND AND AIM

Several epidemiological studies have suggested a link between low birth weight and coronary heart disease; this may be partly due to the association between low birth weight and conventional risk factors. Among the factors involved in the regulation of cardiovascular homeostasis, baroreflexes play a crucial role. The objective of the present study was to investigate if baroreflex sensitivity (BRS) in adulthood is associated with birth weight.

METHODS AND RESULTS

Two hundred and eleven adults from Turin, Italy, aged 22-24 years, were examined in a cross sectional survey. Birth weight, blood pressure, pulse rate, family history of hypertension, anthropometric and environmental parameters and spontaneous baroreflex sensitivity were evaluated. In this study we observed a significant increase in baroreflex sensitivity across the tertiles of birth weight, even after correction for gender, blood pressure and heart rate; in a regression model, birth weight was positively and independently associated with BRS; moreover, BRS showed a significant negative correlation with adult pulse rate.

CONCLUSION

This finding may be helpful in understanding the association between low birth weight and cardiovascular disease outcome in later life, since baroreflex failure is associated with an increased cardiovascular morbidity and mortality.

Can we detect the development of baroreflex sensitivity in humans between 11 and 20 years of age?

The aim of the study was to determine changes of baroreflex sensitivity in humans between 11 and 20 years of age. Continuous 5 min blood pressure recordings using a Finapres were taken in 415 healthy subjects while in a sitting, resting position (breathing at a frequency of 0.33 Hz). Beat-by-beat values of interbeat intervals (IBI) or heart rate, and systolic and diastolic blood pressures were measured. Baroreflex sensitivity in ms/mmHg (BRS) and in mHz/mmHg (BRSf) was determined at an average frequency of 0.1 Hz by spectral analysis. BRS did not correlate with age, but BRSf significantly decreased with age (p < 0.001). BRS correlated with mean IBI (p < 0.001) in all subjects and also in the particular subgroups, but BRSf was IBI-independent. Results of multiregression equations were BRS = 1.37 – 0.56 × age (years) + 0.02 × IBI (ms) (p < 0.001 for BRS vs. age and for BRS vs. IBI); BRSf = 34.74 – 0.97 × age (years) – 0.001 × IBI (ms) (p < 0.001 only for BRS vs. age), where age was measured in years and IBI was measured in ms. The limits of BRS were estimated for the total group: 5th percentile, 3.9; 50th percentile, 9.1; and 95th percentile, 18.7 ms/mmHg; and limits for BRSf were 5th percentile, 8.5; 50th percentile, 16.4; and 95th percentile, 33.6 mHz/mmHg. We conclude that IBI-dependent BRS was unchanged in the particular age groups, but the standardization of BRS on IBI decreased with age. BRSf was IBI-independent and better reflected the development of the BRS.

Influence of age, body mass index, and blood pressure on the carotid intima-media thickness in normotensive and hypertensive patients

We investigated whether body mass index and blood pressure have an additive influence on the carotid intima-media thickness (IMT). In 27 patients treated for hypertension (47.2+/-8.7 years) and 23 normotensive subjects (44.1+/-8.1 years), 24-h recording of blood pressure was performed. The carotid IMT was determined by ultrasonography and baroreflex sensitivity by a spectral method from 5-min recordings of blood pressure. Significant differences between hypertensive and normotensive subjects were observed for carotid IMT (0.60+/-0.08 vs. 0.51+/-0.07 mm; p<0.001) and baroreflex sensitivity (3.5+/-1.8 vs. 5.6+/-2.1 ms/mm Hg; p<0.001). Hierarchical multiple regression analysis (p<0.01) showed that carotid IMT was positively correlated with age (p<0.001) and body mass index (p<0.05) in normotensive subjects. The increased carotid IMT in hypertensive patients was not additively influenced by either age or body mass index. Baroreflex sensitivity decreased with age (p<0.01) and with carotid IMT (p<0.05) in normotensive subjects only. Multiregression analysis showed that an additive influence of age and body mass index on the development of carotid IMT is essential only in normotensive subjects. In hypertensive subjects the influence of blood pressure predominates, as documented by a comparison of the carotid IMT between hypertensive and normotensive subjects.

The link between carotid artery disease and ischemic stroke may be partially attributable to autonomic dysfunction and failure of cerebrovascular autoregulation triggered by Darwinian maladaptation of the carotid baroreceptors and chemoreceptors

Carotid artery stenosis is generally thought to induce stroke by either compromising cerebral perfusion or inciting embolic phenomena. Carotid baroreceptors and chemoreceptors are vital adaptations for cerebrovascular autoregulation that can behave mal-adaptively in the setting of modern diseases such as atherosclerosis. We hypothesize that acute cerebrovascular events may be partially attributable to autonomic dysfunction and cerebrovascular autoregulatory failure secondary to carotid sensor maladaptations. Specifically, we propose that atherosclerotic disease at the carotid bifurcation can interfere with baroreceptor and chemoreceptor function by buffering against accurate detection of physical and chemical parameters. Misperceptions of hypoxia and hypotension can trigger sympathetic bias and autonomic dysfunction which perturb cerebrovascular autoregulation and vasomotor tone, thereby compromising cerebral perfusion. The preferential association of strokes with morning arousal, stress, acute physical activity, winter months, illness, and older age may relate to this phenomenon. Sympathetic bias promotes inflammation and coagulation, a link likely forged during prehistoric evolution when trauma represented a more significant factor in natural selection. In the setting of carotid sensor dysfunction, the resulting inflammation and coagulation can promote acute cardiovascular events. The ensuing cerebral ischemia can induce further derangement of cerebrovascular autoregulation and upregulate adrenergia, inflammation, and coagulation in a feed-forward manner. Inflammation and coagulation can also exacerbate carotid sensor dysfunction by iteratively worsening atherosclerosis. Angioplasty, stenting, and endarterectomy may inadvertently cause acute and chronic carotid sensor dysfunction through manipulation, material interposition, and balloon-induced baroreceptor injury. Acute strokes during these procedures may result from carotid sensor dysfunction rather than embolization. Carotid body and sinus electro-modulation and non-balloon atherectomy represent new methods to prevent or treat cerebrovascular events. Pharmacologic modulation of autonomic balance, such as adrenergic blockade, long presumed contraindicated due to risk of cerebral hypoperfusion, may counter-intuitively offer benefit during acute strokes. Novel diagnostic paradigms may include functional analysis of carotid sensors as well as measurement of the anatomic thickness of calcified and non-calcified plaque near the carotid body. Carotid sensor dysfunction may be a source of systemic sympathetic bias and autonomic dysfunction observed during aging and, by association, many of the ailments associated with senescence. Modulation of carotid sensors may yield pervasive health benefits beyond those found by treating cerebrovascular disease.

Effects of local arteriosclerosis on carotid baroreflex sensitivity and on heart rate and arterial pressure variability in humans

The study examined whether the alterations in heart rate variability (HRV) and baroreflex sensitivity (BRS) observed in patients with coronary artery disease can also be discerned in otherwise healthy subjects with mild-to-moderate arteriosclerosis in the carotid artery bifurcation. Based on the results of carotid duplex ultrasonography, subjects were designated as either having no arteriosclerotic lesions (n = 18), unilateral (n = 19) or bilateral lesions (n = 18) in the bifurcation. Electrocardiograms were recorded and simultaneous and continuous records of arterial pressure were obtained. Resting HRV was determined by calculating the spectral power density in three frequency bands: 0-0.05 Hz [very low frequency (VLF) band], 0.05-0.15 [low frequency (LF) band] and 0.15-2 Hz (high frequency band), whereas the arterial pressure variability (APV) was determined from spectral power density of the VLF and LF bands. Carotid BRS was evaluated by measuring R-R intervals during application of pulse-synchronous graded pressures (40 to -65 mmHg) in a neck-chamber device. Analysis of variance revealed no effect of mild-to-moderate carotid arteriosclerosis on the spectral components of HRV and APV or on BRS. It thus appears that mild-to-moderate asymptomatic carotid arteriosclerosis does not affect carotid BRS, APV or HRV at rest.

Chronotropic response to exercise testing is associated with carotid atherosclerosis in healthy middle-aged men

AIMS

Chronotropic incompetence, an attenuated heart rate (HR) response to exercise, is an independent predictor of cardiovascular mortality, but it is not known whether chronotropic incompetence is related to carotid atherosclerosis. The association between chronotropic incompetence and carotid atherosclerosis in 8567 (age 47.6+/-8.8 years) healthy men was examined.

METHODS AND RESULTS

Chronotropic incompetence was defined as the failure to achieve 85% of the age-predicted maximal HR (APMHR), <80% HR reserve (HRR), and chronotropic response index (CRI). Carotid atherosclerosis was defined, using B-mode ultrasonography, as stenosis >25% and/or intima-media thickness (IMT) of >1.2 mm. In multivariable adjusted logistic regression models, the subjects who achieved less than 85% of APMHR exhibited an odds ratio (OR) of 1.72 [95% confidence intervals (CI): 1.32-2.22] for carotid atherosclerosis. Subjects with <80% of HRR were 1.45 (95% CI: 1.14-1.84) times more likely to have carotid atherosclerosis after multivariate adjustment. Also, the OR of carotid atherosclerosis across quartiles of CRI (highest to lowest) was 1.51 (95% CI: 1.10-2.09) after multivariate adjustment.

CONCLUSION

These results suggest that the chronotropic response to exercise is associated with carotid atherosclerosis, independent of the established risk factors in healthy men, which could contribute to high incidence of cardiovascular diseases in subjects with chronotropic incompetence.

Baroreflex Sensitivity Is Impaired in Bilateral Carotid Atherosclerosis

BACKGROUND AND PURPOSE

The arterial baroreflex is an important determinant of the short-term regulation of blood pressure and cardiovascular variability. The purpose of our study was to determine whether baroreflex sensitivity (BRS) and heart rate (HR) variability are altered in patients with carotid atherosclerosis (CA) and to assess the impact of characteristics of CA on BRS.

METHODS

BRS and HR variability were prospectively evaluated in 75 consecutive patients undergoing carotid duplex examination in our neurosonology unit. Resting BRS was measured with the sequence method. HR variability was evaluated using spectral analysis.

RESULTS

BRS was significantly reduced in patients with bilateral CA compared with patients without CA (P=0.015) and patients with unilateral CA (P=0.045). BRS was unaltered in patients with unilateral CA compared with patients with no CA. BRS was already reduced in mild (stenosis <50%), bilateral CA and was not further impaired in more severe CA. The association of BRS impairment with bilateral CA remained significant after adjustment for age, hypertension, and a history of stroke or transient ischemic attack. The study of HR variability demonstrated a reduction in the power of high-frequency band in patients with bilateral CA compared with patients with unilateral CA or without CA (P=0.015).

CONCLUSIONS

Bilateral CA is associated with an impairment of BRS and a shift of the sympathovagal balance toward a relative decrease of the parasympathetic component of HR variability. These changes are already present in mild, bilateral CA.

Diabetic neuropathy is a more important determinant of baroreflex sensitivity than carotid elasticity in type 2 diabetes

The object of this study was to evaluate the contribution of carotid distensibilty on baroreflex sensitivity in patients with type 2 diabetes mellitus with at least 2 additional cardiovascular risk factors. Carotid distensibility was measured bilaterally at the common carotid artery in 79 consecutive diabetic patients and 60 matched subjects without diabetes. Spontaneous baroreflex sensitivity assessment was obtained using time and frequency methods. Baroreflex sensitivity was lower in diabetic subjects as compared with nondiabetic control subjects (5.25+/-2.80 ms/mm Hg versus 7.55+/-3.79 ms/mm Hg; P<0.01, respectively). Contrary to nondiabetic subjects, diabetic subjects showed no significant correlation between carotid distensibility and baroreflex sensitivity (r2=0.08, P=0.04 and r2=0.04, P=0.13, respectively). In diabetic subjects, baroreflex sensitivity was significantly lower in subjects with peripheral neuropathy than in those with preserved vibration sensation (4.1+/-0.5 versus 6.1+/-0.4 ms/mm Hg, respectively; P=0.005). Age in nondiabetic subjects, diabetes duration, systolic blood pressure, peripheral or sensitive neuropathy, and carotid distensibility were introduced in a stepwise multivariate analysis to identify the determinants of baroreflex sensitivity. In diabetic patients, neuropathy is a more sensitive determinant of baroreflex sensitivity than the reduced carotid distensibility (stepwise analysis; F ratio=5.1, P=0.028 versus F ratio=1.9, P=0.16, respectively). In diabetic subjects with 2 additional cardiovascular risk factors, spontaneous baroreflex sensitivity is not related to carotid distensibility. Diabetic subjects represent a particular population within the spectrum of cardiovascular risk situations because of the marked neuropathy associated with their metabolic disorder. Therefore, neuropathy is a more significant determinant of baroreflex sensitivity than carotid artery elasticity in patients with type 2 diabetes.