Basal blood pressure variability and reactivity of blood pressure to emotional stress in essential hypertension

Pain perception during baroreceptor unloading by lower body negative pressure

BACKGROUND

People with high blood pressure have reduced sensitivity to pain, known as blood pressure hypoalgesia. One proposed mechanism for this is altered baroreceptor sensitivity. In healthy volunteers, stimulating the carotid baroreceptors causes reduced sensitivity to acute pain; however, this effect may be confounded by a rise in blood pressure due to baroreflex stimulation. The present study tests whether baroreceptor unloading contributes to the physiological mechanism of blood pressure-related hypoalgesia.

METHODS

In the present study, pain perception to thermal stimulation of the forearm was studied in 20 healthy volunteers during baroreceptor unloading by lower body negative pressure (LBNP) at -5 and -20 mmHg. Blood pressure and heart rate were measured continuously throughout. To address issues relating to stimulation order, the sequence of LBNP stimulation was counterbalanced across participants.

RESULTS

Increased heart rate was observed at a LBNP of -20 mmHg, but not -5 mmHg, but neither stimulus had an effect on blood pressure. There was no change in warm or cold sensory detection thresholds, heat or cold pain thresholds nor perceived pain from a 30s long thermal heat stimulus during LBNP.

CONCLUSION

Therefore, baroreceptor unloading with maintained systemic blood pressure did not alter pain perception. The current study does not support the hypothesis that an altered baroreflex may underlie the physiological mechanism of blood pressure-related hypoalgesia.

SIGNIFICANCE

This work provides evidence that, when measured in normotensive healthy young adults, the baroreflex response to simulated hypovolaemia did not lead to reduced pain sensitivity (known as blood pressure hypoalgesia).

Physiological reactivity to acute mental stress in essential hypertension-a systematic review

Objective

Exaggerated physiological reactions to acute mental stress (AMS) are associated with hypertension (development) and have been proposed to play an important role in mediating the cardiovascular disease risk with hypertension. A variety of studies compared physiological reactivity to AMS between essential hypertensive (HT) and normotensive (NT) individuals. However, a systematic review of studies across stress-reactive physiological systems including intermediate biological risk factors for cardiovascular diseases is lacking.

Methods

We conducted a systematic literature search (PubMed) for original articles and short reports, published in English language in peer-reviewed journals in November and December 2022. We targeted studies comparing the reactivity between essential HT and NT to AMS in terms of cognitive tasks, public speaking tasks, or the combination of both, in at least one of the predefined stress-reactive physiological systems.

Results

We included a total of 58 publications. The majority of studies investigated physiological reactivity to mental stressors of mild or moderate intensity. Whereas HT seem to exhibit increased reactivity in response to mild or moderate AMS only under certain conditions (i.e., in response to mild mental stressors with specific characteristics, in an early hyperkinetic stage of HT, or with respect to certain stress systems), increased physiological reactivity in HT as compared to NT to AMS of strong intensity was observed across all investigated stress-reactive physiological systems.

Conclusion

Overall, this systematic review supports the proposed and expected generalized physiological hyperreactivity to AMS with essential hypertension, in particular to strong mental stress. Moreover, we discuss potential underlying mechanisms and highlight open questions for future research of importance for the comprehensive understanding of the observed hyperreactivity to AMS in essential hypertension.

Comparisons of tri-ponderal mass index and body mass index in discriminating hypertension at three separate visits in adolescents: A retrospective cohort study

OBJECTIVE

To estimate whether the new obesity indicator tri-ponderal mass index (TMI) has a better capacity to predict adolescent hypertension (HTN) and HTN subtypes at three separate blood pressure (BP) visits than the conventionally used body mass index (BMI).

METHODS

A total of 36,950 adolescents who had initial normal BP from 2012 to 2019 were included in Suzhou, China. HTN was defined as having three separate visits of elevated BP in 2020. The area under the receiver-operating characteristic curve (AUC), false-positive rate, false-negative rate, total misclassification rates, net reclassification improvement (NRI), and integrated discrimination improvement were calculated to compare the discriminative ability of HTN between BMI and TMI.

RESULTS

TMI had better predictive abilities than BMI among all of the participants when predicting HTN (difference in AUC = 0.019, 95% CI = 0.007-0.031; NRI = 0.067, 95% CI = 0.008-0.127) and isolated systolic hypertension (difference in AUC = 0.021, 95% CI = 0.005-0.036; NRI = 0.106, 95% CI = 0.029-0.183). The difference in prediction abilities between BMI and TMI was more obvious in the subgroup of age ≥16. Also, TMI outperformed BMI in predicting adolescent HTN in girls but not in boys.

CONCLUSION

Compared with BMI, TMI may have a better predictive capacity for HTN, particularly in girls and older adolescents. TMI has the potential to be used as an effective predictor for HTN in clinic practice. Further studies are needed to verify the utility of TMI.

Depiction of Physiological Homeostasis by Self-Coupled System and Its Significance

The negative feedback system (NFS) was regarded as the basic unit of regulation of physiological homeostasis for more than 70 years. However, NFS-based depiction possesses some limitations. The self-coupled system (SCS), a non-stop system in which the output of the current moment becomes the input of the next moment, can also be utilized to depict homeostasis. In SCS-based depiction, all of the related regulatory mechanisms of a homeostasis are regarded as an entity. Then, homeostatic dynamics can be expressed by simple mathematical language. A new disease group was revealed and some useful inferences were obtained through mathematical deduction. They were supported by published studies. SCS-based depiction of homeostasis should be a requisite supplement to medical knowledge systems based on NFS.

Hypertension Prevalence Based on Three Separate Visits and Its Association With Obesity Among Chinese Children and Adolescents

Background: Clinical practice guidelines recommended that hypertension in children and adolescents should be defined based on elevated blood pressure (BP) on at least three separate occasions. Therefore, in the present study, we aimed to estimate the prevalence of hypertension based on three separate visits among Chinese children and adolescents and to examine its relationship with obesity. Methods: A school-based cross-sectional survey was performed in children and adolescents in Jinan, China between September 2012 and September 2014. A total of 7,832 children and adolescents aged 6-17 years were included. Anthropometric data and BP were measured by trained examiners. Elevated BP was defined as BP ≥ 95th percentile for age and sex based on the Chinese reference data. Participants with elevated BP at the first visit underwent a second visit 2 weeks later, and a third visit was conducted if BP was still high at the second visit. Hypertension was defined as having an elevated BP at all three visits. Obesity was defined in three ways by using body mass index, waist circumference, and waist-to-height ratio. Results: The prevalence of elevated BP decreased substantially across three separate visits, with the prevalence of 17.2, 8.6, and 4.9%, respectively. Obesity was an independent risk factor for elevated BP during each visit. Based on the body mass index, obesity was associated with higher risk of elevated BP, with the adjusted odds ratios (ORs) and 95% confidence intervals (CIs) of 8.6 (6.8-11.0), 12.5 (9.1-17.3), and 14.0 (8.9-22.2), respectively, at the first, second and third visit. The ORs of elevated BP were similar in association with obesity defined by waist circumference or waist-to-height ratio. Conclusions: The prevalence of hypertension based on three visits was ~5% in Chinese children and adolescents. There was a dose-response relationship between obesity and elevated BP across three visits.

Association between within-visit systolic blood pressure variability and development of pre-diabetes and diabetes among overweight/obese individuals

Short-term blood pressure variability is associated with pre-diabetes/diabetes cross-sectionally, but there are no longitudinal studies evaluating this association. The objective of this study is to evaluate the association between within-visit systolic and diastolic blood pressure variability and development of pre-diabetes/diabetes longitudinally. The study was conducted among eligible participants from the San Juan Overweight Adults Longitudinal Study (SOALS), who completed the 3-year follow-up exam. Participants were Hispanics, 40-65 years of age, and free of diabetes at baseline. Within-visit systolic and diastolic blood pressure variability was defined as the maximum difference between three measures, taken a few minutes apart, of systolic and diastolic blood pressure, respectively. Diabetes progression was defined as development of pre-diabetes/diabetes over the follow-up period. We computed multivariate incidence rate ratios adjusting for baseline age, gender, smoking, physical activity, waist circumference, and hypertension status. Participants with systolic blood pressure variability ≥10 mmHg compared to those with <10 mmHg, showed higher progression to pre-diabetes/diabetes (RR = 1.77, 95% CI: 1.30-2.42). The association persisted among never smokers. Diastolic blood pressure variability ≥10 mmHg (compared to <10 mmHg) did not show an association with diabetes status progression (RR = 1.20, 95% CI: 0.71-2.01). Additional adjustment of baseline glycemia, C-reactive protein, and lipids (reported dyslipidemia or baseline HDL or triglycerides) did not change the estimates. Systolic blood pressure variability may be a novel independent risk factor and an early predictor for diabetes, which can be easily incorporated into a single routine outpatient visit at none to minimal additional cost.

The effects of social context on the hormonal and behavioral responsiveness of human fathers

We tested first-time fathers with their 22-month old toddlers to determine whether social context variables such as pre-test absence from the child and presence of the mother affected physiological measures associated with paternal responsiveness. Heart rate and blood pressure readings as well as blood samples to determine prolactin, testosterone and cortisol levels were taken before and after the 30-min father-toddler interactions. Fathers were tested on a day when they were away from their child for several hours before testing ('without-child' day) and on another day where they remained with their child throughout the day ('with-child' day). Most measures decreased over the 30-min test period but relative decreases were context-dependent. Men maintained higher prolactin levels when they were away from their children longer before testing on the 'without-child' day. Cortisol levels decreased during both tests and they decreased more on the 'with-child' day for men who had spent more time alone with their toddler before the test. Heart-rate and diastolic (but not systolic) blood pressure decreased more on the 'with-child' day than on the 'without-child' day. Fathers' testosterone levels decreased when their partners were less involved in the interactions. Compared to men with high responsiveness ratings on both days, men whose responsiveness increased after being away from their child on the 'without-child' day maintained higher systolic blood pressure and had a greater decrease in testosterone levels. We conclude that context may be more important in determining fathers' physiological responses to child contact than has previously been appreciated, particularly for some individuals.

Spectral change in heart rate variability in response to mental arithmetic before and after the beta-adrenoceptor blocker, carteolol

Spectral analysis of heart rate fluctuation was evaluated before and after administration of carteolol, a non-selective beta-adrenoceptor-blocker, to investigate the neural regulatory mechanisms underlying the haemodynamic changes induced by mental stress. Mental stress increased blood pressure and heart rate, with an increased low frequency band, and low frequency/high frequency ratio of the power spectral analysis which are indices of sympathetic activity. Carteolol did not change basal and pre-mental stress measurements of blood pressure, heart rate and spectral density. However, carteolol altered the response to mental stress with a decrease in spectral density of the low frequency band and low frequency/high frequency ratio, and an increase in the high frequency component. These results confirm that mental stress elevates blood pressure by activating the sympathetic nervous system, and suggest that blockade of the beta-adrenoceptor attenuates the pressor response by preventing the autonomic responses to mental stress.

Cardiovascular reactivity to stress: an examination of familial trends

Mental stress elicits changes in cardiovascular functioning such as increases in blood pressure and heart rate and leads to biochemical changes which may facilitate the development of cardiovascular disease. This study examined the correlations between levels of cardiovascular change seen in healthy fathers and their sons who underwent stress testing (cold pressor test and mental arithmetic). No correlation between fathers' and sons' levels of reactivity were found. Certain personality traits such as hostility and anger directed inward have previously been shown to correlate with both reactivity and presence of arterial disease. In this study, hostility levels and assertiveness levels were measured and were found to correlate modestly with reactivity in the fathers but not in the sons. Sons showed less assertiveness and greater hostility overall; thus, restriction of the range of these variables may limit potential correlations with physiological measures in this group. Finally, although no family trends were observed, several of the adolescents did show extreme changes under stress, suggesting reactivity is a trait which is expressed early in life.

Circumstances surrounding aneurysmal subarachnoid hemorrhage

The circumstances surrounding aneurysmal subarachnoid hemorrhage were investigated in a group of 500 consecutive patients admitted to a neurosurgical center. Subarachnoid hemorrhage occurred during stressful events in 42.8% of the patients, during nonstrenuous activities in 34.4%, and during rest or sleep in 11.8%. The activities or events preceding subarachnoid hemorrhage were not known in the remaining 11.0%. Men were more likely to have suffered their hemorrhage during stressful events than women (54.1% versus 36.6%; p less than 0.00025). Only 30.1% of aneurysms arising from the internal carotid artery ruptured during stressful events compared with 48.1% of aneurysms at other locations (p less than 0.005). Physiological responses to the various activities and events are discussed as they may relate to mechanisms underlying aneurysmal subarachnoid hemorrhage. Two important factors in the precipitation of aneurysmal rupture are increased arterial blood pressure and decreased cerebrospinal fluid pressure around the aneurysm. These factors result in a high transmural pressure and concomitant wall stress. Physical exertion, activities involving the Valsalva maneuver, and emotional strain are associated with an increase in blood pressure and frequently preceded subarachnoid hemorrhage. Fluctuations in cerebrospinal fluid pressure around the aneurysm mainly occur during Valsalva's maneuver and postural changes.

Effects of carotid sinus nerve stimulation at different times in the respiratory and cardiac cycles on variability of heart rate and blood pressure of normotensive and renal hypertensive dogs

It was the purpose of the present study to determine (1) whether or not there exists a common respiratory and cardiac cycle time effect of the baroreceptor control of heart rate (HR) and blood pressure (BP) in spontaneously breathing anaesthetized dogs and (2) whether this effect, if present, is abnormal in dogs with renal hypertension. The baroreflex responses were evoked by brief low-intensity electrical carotid sinus nerve stimulation (CSNS) triggered by the R-wave in the electrocardiogram with an adjustable delay (0-210 ms) and positioned in either inspiration or expiration. All baroreceptor afferent nerves were intact. Brief CSNS had no noticeable effect on breathing. The responses of means of HR, respiratory sinus arrhythmia (RSA), and systolic and diastolic respiratory blood pressure waves (RBPWsyst, RBPWdiast) to CSNS were not different for normotensive and hypertensive dogs. No cardiac, but a small respiratory cycle time effect on means of HR, BPsyst and BPdiast was observed. The magnitude of RSA and RBPWdiast was markedly enhanced for expiratory CSNS at each delay after the R-wave. Inspiratory CSNS diminished the magnitude of RSA and RBPW only if applied during systole, and become ineffective for delays greater than 200 ms after the R-wave. During both respiratory phases, CSNS was elevated at times of central presentation of the natural sinoaortal baroreceptor discharges (120 ms and 70 ms, respectively). The magnitudes of RSA and RBPW were influenced simultaneously and in the same way by CSNS throughout. It is concluded that, under the present experimental conditions, RSA and RBPW have a common central origin.

Lack of correlation between clinic and 24 hour ambulatory blood pressure in subjects participating in a therapeutic drug trial

Although previous studies document that blood pressure measured in the clinic may differ significantly from blood pressure recorded over 24 hours, the impact of these differences on patient selection for therapeutic drug trials is unknown. A placebo controlled double-blind evaluation of an experimental antihypertensive agent was conducted. Of 30 patients entered, 21 were admitted to the active drug phase of the protocol on the basis of a clinic supine diastolic blood pressure greater than or equal to 95 mmHg; 9 subjects with lower levels of diastolic blood pressure were dropped. Noninvasive ambulatory blood pressure monitoring was performed during the placebo period. Comparison of the two subgroups demonstrated similar levels of 24 hour blood pressure (142 +/- 13/86 +/- 7 vs 137 +/- 10/82 +/- 10). Analysis of individual patient data showed that 24 hour mean diastolic blood pressure was apparently normal (less than or equal to 80 mmHg) in 5/21 (24%) "admitted" and 3/9 (33%) "dropped" subjects. Circadian blood pressure pattern were similar in the two subgroups. A statistically large difference was noted between clinic and 24 hour blood pressures in the "admitted" subgroup (20 +/- 18/13 +/- 7 vs 7 +/- 12/4 +/- 6, p less than 0.08/p less than 0.001), suggesting that patients exhibiting a marked blood pressure rise in the clinic setting were preferentially selected.

Psychophysiologic stress testing as a predictor of mean daily blood pressure

This study describes correlations between the mean daily blood pressures determined by ambulatory blood pressure monitoring and those obtained during psychophysiologic stress testing. Seven normotensive and 21 hypertensive persons were monitored for hemodynamic changes in the laboratory while undergoing various standardized, low-challenge psychophysiologic tests. The same persons then had their blood pressure monitored with an ambulatory unit for the rest of the day. The laboratory "resting" pressure used was derived by averaging measurements for mean blood pressure obtained in three positions: standing, sitting, and supine. The "stress" pressure used was the mean blood pressure obtained by averaging three readings taken during videogame playing. A good correlation (r = 0.78) between work-time blood pressure and the laboratory stress pressure was noted. The correlation was improved (r = 0.8) when the averages of laboratory resting and stress values were used. A relationship was also noted between peak pressures obtained during the laboratory testing and those obtained during work-time by ambulatory monitoring.

Respiratory variations in arterial blood pressure and heart rate in normotensive and renal hypertensive dogs

Respiratory sinus arrhythmia (RSA), systolic and diastolic respiratory blood pressure waves (RBPWsyst, RBPWdiast), mean heart rate (HR), mean respiratory frequency (RF) and the heart beat to respiratory cycle ratio (HB/RC) were measured in 23 spontaneously breathing, normotensive or renal hypertensive dogs under light anaesthesia. No significant differences were found between conditions of normal and chronically elevated blood pressure. All these parameters were analyzed statistically by means of linear regression analysis and rank correlation coefficient (rs). A correlation was found to exist between RSA and mean systolic blood pressure (negative), RF (negative), RBPWsyst (positive), RBPWdiast (positive). RF correlated with both HB/RC (negative) and RBPWsyst (negative). A correlation was also seen between PA and both BPsyst (positive) and BPdiast (positive), BPsyst and BPdiast (positive) and between HR and RBPWdiast (negative); however, all the remaining, theoretically possible correlations were not significant. The results may be referred to resonance mechanisms in a common nervous oscillator system.

General mechanism of chronic diseases

In a human, the cells function adequately to the needs of the organism, and to their own needs. Consequently, adequate cell function is comprised of the organism-oriented, and cell-oriented functions. It is suggested that an independent stage in the pathogenesis of a chronic disease exists which so far has not been considered. This is the disturbance of the cell-oriented function of the cells involved. This initial stage may last for years and decades, whereas function of the organ remains preserved. Organism-oriented cellular function appears to become involved in the pathologic process long after the disease has actually started. At this time the cells themselves are severely impaired, and as a result a disease acquires its progressive, irreversible course. Pathogenesis of atherosclerosis is considered as an example of the above-mentioned developments.

Cognitive stress and cardiovascular reactivity. I. Relationship to hypertension

This report reviews the current literature relating cognitive stress and cardiovascular reactivity to the development of hypertension. Cardiovascular reactivity may refer to a change in one or several cardiovascular parameters as a function of exposure to a cognitive stressor, e.g., systolic BP, HR, etc. The cognitive stressors involve laboratory-based mental tasks such as mental mathematics, choice reaction time, and stressful interviews. The current findings suggest that the reactivity literature may have something unique to contribute to the study of hypertension. Prospective studies linking clinical hypertension to early reactivity are few in number. However, reactivity appears to be reliable within individuals over short periods of time (3 months), and individuals at the upper end of the reactivity distribution may have a higher incidence of future hypertension than those at the lower end. Reactivity may also contribute to two other dimensions of hypertension. Subjects with positive family histories of hypertension may be expected to be among the most reactive to cognitive stress, and among established hypertensive individuals, the reactivity to stress may be correlated with casual BP lability. Several avenues have been suggested through which a hyperresponsiveness to mental stress may be implicated in the development of hypertension. Repeated stressor episodes might influence vascular rigidity, through direct alteration of smooth muscle morphology and downregulation of the alpha receptor or through a process of autoregulation of CO, blood volume, and changes in renal regulation of water and sodium balance.