Effect of beta blockade with and without sympathomimetic activity (ISA) on sympathovagal balance and baroreflex sensitivity

Baroreflex Sensitivity and Long-Term Dementia Risk in Older Adults

BACKGROUND

Increased blood pressure (BP) variability is linked to dementia risk, but the relationship between baroreflex sensitivity (BRS), a fundamental mechanism for maintaining stable BP, and dementia risk is undetermined.

METHODS

We tested the hypothesis that impaired BRS is associated with increased dementia risk in 1819 older adults (63% women; age, 71.0±6.3 years) from the community-based Rotterdam Study. Cardiac BRS was determined from a 5-minute beat-to-beat BP recording at supine rest between 1997 and 1999. Cardiac BRS measures the correlation between changes in consecutive beat-to-beat systolic BP and subsequent responses in heartbeat intervals, with a higher value indicating better BRS. The primary outcome was incident dementia ascertained from baseline through January 1, 2020; the secondary outcome was all-cause mortality.

RESULTS

During a median follow-up of 14.8 years, 421 participants developed dementia. The association of cardiac BRS with dementia risk differed by antihypertensive medication use (Pinteraction=0.03) and was only observed in participants not taking antihypertensives. Specifically, in those not taking antihypertensive medication, reduced BRS was associated with a higher risk of dementia (adjusted hazard ratio comparing bottom versus top quintiles, 1.60 [95% CI, 1.07-2.40]; Ptrend=0.02). Reduced BRS was also associated with an increased risk of death (corresponding hazard ratio, 1.76 [95% CI, 1.32-2.35]). The association remained after adjusting for average BP and BP variability.

CONCLUSIONS

Impaired BRS partly explains hypertension-related brain damage and excessive dementia risk beyond conventional BP measures, making it a potential novel biomarker for the early detection and prevention of dementia.

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.

Baroreflex sensitivity is higher during acute psychological stress in healthy subjects under β-adrenergic blockade

Acute psychological stress challenges the cardiovascular system with an increase in BP (blood pressure), HR (heart rate) and reduced BRS (baroreflex sensitivity). β-adrenergic blockade enhances BRS during rest, but its effect on BRS during acute psychological stress is unknown. This study tested the hypothesis that BRS is higher during acute psychological stress in healthy subjects under β-adrenergic blockade. Twenty healthy novice male bungee jumpers were randomized and studied with (PROP, n=10) or without (CTRL, n=10) propranolol. BP and HR responses and BRS [cross-correlation time-domain (BRSTD) and cross-spectral frequency-domain (BRSFD) analysis] were evaluated from 30 min prior up to 2 h after the jump. HR, cardiac output and pulse pressure were lower in the PROP group throughout the study. Prior to the bungee jump, BRS was higher in the PROP group compared with the CTRL group [BRSTD: 28 (24-42) compared with 17 (16-28) ms·mmHg-1, P<0.05; BRSFD: 27 (20-34) compared with 14 (9-19) ms·mmHg-1, P<0.05; values are medians (interquartile range)]. BP declined after the jump in both groups, and post-jump BRS did not differ between the groups. In conclusion, during acute psychological stress, BRS is higher in healthy subjects treated with non-selective β-adrenergic blockade with significantly lower HR but comparable BP.

Increased baroreflex sensitivity and heart rate variability in migraine patients

OBJECTIVES

We investigated whether spontaneous baroreflex sensitivity and heart rate variability (HRV) are different in migraine patients compared to healthy controls.

MATERIAL AND METHODS

Sixteen female migraine patients without aura aged 18-30 years and 14 age-matched healthy female controls were included. Continuous finger blood pressure and ECG were measured supine during paced breathing in the laboratory. Continuous finger blood pressure was measured the following 24-h period. Spontaneous baroreflex sensitivity (time-domain cross correlation baroreflex sensitivity) as well as HRV parameters were calculated.

RESULTS

Spontaneous baroreflex sensitivity measured in the 24-h period was increased in patients (20.6 ms/mmHg) compared to controls (15.7 ms/mmHg, P = 0.031). HRV parameters were increased during paced breathing in patients (P < 0.045).

CONCLUSIONS

The results suggest that central hypersensitivity in migraine also includes cardiovascular reactivity and may be important for the understanding of the mechanisms for the effect of antihypertensive drugs for migraine prophylaxis.

Effect of 35 years beta-adrenergic blockade therapy on autonomic cardiovascular modulation. A case study

The influence of long duration beta-blockade on autonomic and cardiovascular function remains not completely understood. The aim of this study was to evaluate the effect of long duration beta-adrenergic blockade treatment for hypertension control, on autonomic cardiovascular control in a 78-year-old male patient in relation to population findings. Heart rate variability was determined in the frequency domain (Total power, low frequency power and high frequency power), during baseline (supine and standing) and during 24 hour Holter recording. Results were compared with heart rate and heart rate variability data obtained from a normal healthy male population as a function of age. Circadian rhythm remained present. Heart rate during daytime was lower compared to the population group. None of the heart rate variability parameters were different from the normal population age group. Our results show that after 35 years of beta-blockade treatment, autonomic modulation of cardiac function remains within normal limits for that age group. Blood pressure remained at the higher limits (120-150/60-80 mmHg), but under control.

The Leu7Pro polymorphism of preproNPY is associated with decreased insulin secretion, delayed ghrelin suppression, and increased cardiovascular responsiveness to norepinephrine during oral glucose tolerance test

CONTEXT

Neuropeptide Y (NPY) plays a role in angiogenesis, cardiovascular regulation, and hormone secretion. The leucine7 to proline7 (Leu7Pro) polymorphism of preproNPY is associated with vascular diseases and has an impact on hormone levels in healthy subjects.

OBJECTIVE

The current study investigated the role of the Leu7Pro polymorphism in metabolic and cardiovascular autonomic regulation.

DESIGN AND SUBJECTS

A 5-h oral glucose tolerance test was performed on 27 healthy volunteers representing two preproNPY genotypes (Leu7/Pro7 and Leu7/Leu7) matched for age, sex, body mass index and physical activity.

MAIN OUTCOME MEASURES

Simultaneously we performed cardiovascular autonomic function tests and plasma measurements of sympathetic transmitters, glucose, insulin, and ghrelin.

RESULTS

The subjects with Leu7/Pro7 genotype had decreased plasma NPY, norepinephrine (NE), and insulin concentrations and insulin to glucose ratios. The suppression of ghrelin concentrations after glucose ingestion was delayed in these subjects. They also had increased heart rate variability indices and baroreflex sensitivity. However, they displayed significant negative association of NE concentration with variability of low-frequency R-R-intervals and with baroreflex sensitivity.

CONCLUSIONS

The Leu7Pro polymorphism of preproNPY is related to decreased level of basal sympathetic activity, decreased insulin secretion, and delayed ghrelin suppression during oral glucose tolerance test. The increased responsiveness of autonomic functions to NE associated with the polymorphism may be connected to increased cardiovascular vulnerability.

Relation between actual heart rate and autonomic effects of beta blockade in healthy men

This study evaluated the effect of beta blockade on cardiac autonomic control and its dependence on heart rate change. The relations between RR interval duration, heart rate variability (HRV), and baroreflex sensitivity (BRS) were studied in 111 healthy men and in 21 male volunteers before and after a 100-mg oral dose of metoprolol. HRV and BRS correlated significantly with mean RR (r = 0.39, r = 0.57). Metoprolol administration increased both mean RR (from 996 to 1,176 ms, p <0.001), BRS from 24 to 36 ms/mm Hg (p = 0.003), and the SD of RR from 61 to 74 ms (p = 0.05). However, metoprolol-induced changes of HRV and BRS became insignificant (p = 0.69 and 0.48) after they were normalized to the same cycle length, suggesting that the improvement of cardiac autonomic control after beta blockade could be explained by a change of heart rate.

Hopelessness is associated with decreased heart rate variability during championship chess games

OBJECTIVE

Clinical observations suggest that negative affects such as helplessness/hopelessness (HE/HO) may induce autonomic duration; affects were assessed for every move after reconstruction of the games. In all games compiled, 18 situation of intense confidence/optimism and 20 of intense helplessness/hopelessness were observed.

RESULTS

Intense affects of HE/HO were associated with decreasing HF-HRV (Fisher exact test, p =.003), increasing "nervousness" (p =.0005), decreasing "optimism" (p =.0005), and decreasing "calmness" (p =.0005).

CONCLUSIONS

Investigation of championship chess game players with an ELO strength > or = 2300 in a natural field setting revealed increasing HE/HO being associated with reduced HF-HRV suggestive of vagal withdrawal. Thus, our data may help link negative mood states, autonomic nervous system disturbances, and cardiac events.

Cardiovascular effects of ophthalmic 0.5% timolol aqueous solution and 0.1% timolol hydrogel

The objective of this randomized, double-masked, cross-over study was to compare the cardiovascular effects of two glaucoma formulations, ophthalmic 0.5% timolol aqueous solution and 0.1% timolol hydrogel. Twenty-four young healthy subjects received for 2 weeks either twice daily 0.5% timolol solution or once daily 0.1% timolol hydrogel. Heart rate (HR), blood pressure, atrio-ventricular conduction (PR interval), corrected QT time (QTc) and heart rate variability (HRV) were measured in supine position and during head-up tilted position. The mean peak concentrations of timolol in plasma were significantly higher after administration of 0.5% aqueous solution than after 0.1% hydrogel. A 0.5% timolol aqueous solution decreased HR on average by 3 bpm in supine position and by 7 bpm in head-up tilted position while no significant effects were observed with 0.1% timolol hydrogel. During tilt test HR was significantly lower after administration of timolol aqueous solution than after timolol hydrogel (mean +/- SD, 77 +/- 11 bpm versus 86 +/- 13 bpm, P < 0.05). Timolol aqueous solution slightly decreased QTc during tilt (5.9 +/- 5.6 ms, P < 0.01). During tilt tests, timolol aqueous solution slightly increased atrio-ventricular conduction (7.2 ms, P = 0.02). No significant differences were found in HRV. These results indicate that in healthy volunteers, ophthalmic 0.5% timolol aqueous solution produces more pronounced cardiac beta-blocking effects than 0.1% timolol hydrogel.

Cardiovascular indices of peripheral and central sympathetic activation

OBJECTIVE

A number of sympathetic nervous system (SNS) parameters have been used in cardiovascular psychophysiology. This study aimed to describe the pattern and redundancy of a set of SNS parameters during peripherally induced changes of cardiac sympathetic activation and reflex modulation of central SNS control. Preejection period (PEP) was assessed as a marker of peripheral sympathetic activation. Low-frequency blood pressure variability (BPV) was assessed as an estimate of central SNS control.

METHODS

Peripheral beta-sympathetic stimulation and blockade were achieved with epinephrine and esmolol hydrochloride (beta1-blockade), respectively. Changes in central SNS output were induced by loading and unloading arterial baroreceptors with norepinephrine and nitroprusside sodium, respectively. This single-blinded, crossover study in 24 healthy men also included two placebo control periods. PEP was derived from impedance cardiography and adjusted individually for heart rate. BPV was calculated by power spectral analyses of beat-to-beat heart rate and systolic blood pressure (Finapres system) data.

RESULTS

PEP decreased during epinephrine infusion (-40.1 +/- 3.8 ms, p <.0001) and increased during esmolol infusion (+6.6 +/- 3.5 ms, p =.05). PEP was shortened after central SNS activation by nitroprusside (-16.8 +/- 2.9 ms, p < 0.0001). Systolic BPV in the low-frequency range (0.07-0.14 Hz, Mayer waves) increased during nitroprusside infusion (+0.44 +/- 0.19 ln mm Hg(2), p =.03) and decreased during norepinephrine infusion (-0.67 +/- 0.13 ln mm Hg(2), p < 0.0001). Low-frequency BPV did not change significantly during epinephrine or esmolol infusion.

CONCLUSIONS

Our data provide empirical evidence of separable peripheral and central sympathetic response components. The combined report of low-frequency BPV and PEP gives distinct information on both central SNS control and the level of sympathetic cardiac activation achieved.