Stimulus-Specific Patterns of Cardiovascular Reactivity in Type A and B Subjects: Evidence for Enhanced Vagal Reactivity in Type B

Recent evidence suggests that the differences in cardiovascular reactivity between individuals exhibiting the Type A behavior pattern and those that do not are not limited to excessive betaadrenergic reactivity in Type A's. Research also suggests the possibility of a tendency for enhanced alpha-adrenergically and vagally mediated cardiovascular reactivity in Type B's. In the present study, Type A and Type B subjects were exposed to stressor stimuli known to elicit either betaadrenergic or alpha-adrenergic and vagal responses in the cardiovascular system. Heart rate, blood pressure, and forearm blood flow and vascular resistance responses were measured. The two Types did not differ in response to the beta-adrenergic stimulus (mental arithmetic). However, the alpha-adrenergic/vagal stimulus (cold face stimulus) produced more prolonged heart rate and blood flow responses in Type B subjects. Results suggest that Type B's show hyperreactivity (compared to Type A) when alpha-adrenergic or vagal cardiovascular responses are elicited. The nature of this hyperreactivity suggests possible mechanisms for reduced cardiovascular disease risk in Type B individuals.     

Beta‐adrenergic receptor gene polymorphisms and cardiovascular reactivity to stress in Black adolescents and young adults

Cardiovascular reactivity to stress and β‐adrenergic receptor (β‐AR) function may contribute to the development of hypertension. As Black Americans have an increased risk of hypertension, we evaluated associations between β₁‐AR (Arg389Gly) and β₂‐AR (Arg16Gly, Gln27Glu) gene variants and cardiovascular reactivity in 500 Black youth. Heart rate, preejection period, total peripheral resistance, and blood pressure reactivity were measured during cold and psychological stress. The Arg389Gly polymorphism in the β₁‐AR was associated with preejection period reactivity in males but not in females. The Arg16Gly polymorphism in the β₂‐AR was associated with diastolic blood pressure reactivity only during video game stress. An association between the Gln27Glu polymorphism in the β₂‐AR and vascular reactivity depended on sex. Thus, specific patterns of associations emerged between genetic variations in β‐ARs and cardiovascular reactivity in young Blacks.     

Parental history of hypertension and cardiovascular response to stress in black and white men

White offspring of hypertensives typically exhibit an elevated cardiovascular response to stress. Studies of Black offspring of hypertensives have been fewer, with inconsistent results. This may be due, in part, to incomplete characterizations of hemodynamic responses. This study examines cardiovascular reactivity in Black and White offspring of hypertensives with a particular focus on vascular resistance responses. A total of 62 healthy normotensive men, 41 with a parental history of hypertension (PH+: 21 Blacks, 20 Whites), and 21 without parental hypertension (PH-: 7 Blacks, 14 Whites) engaged in a series of laboratory tasks. Both Black and White PH+ participants exhibited elevated diastolic blood pressure (DBP) responses, but to different patterns of stressor tasks. Familial differences in total peripheral resistance response were also obtained for Black and White participants in a comparison across all tasks, but were particularly evident in tasks when PH+ participants had elevated DBP responses. These results suggest that a parental history of hypertension is an important moderator of cardiovascular, and in particular peripheral vascular, responses to stress in Black and White individuals. This research was supported in part by National Institutes of Health Grants HL31533 and RR00046. We thank Doris Murrell, Antonia Vincent, Nancy Pettee, and Deborah Jansen for their technical assistance.     

Children''s Cardiovascular Reactivity: Stability of Racial Differences and Relation to Subsequent Blood Pressure over a One-Year Period

After measuring blood pressure and heart rate at rest and during a video game procedure in 477 children enrolled in 3rd grade, 434 (91%) children had these measurements repeated a year later in 4th grade. Black children demonstrated greater blood pressure and heart rate reactivity than White children in both years, and an increase in heart rate reactivity from 3rd to 4th grade. Gender effects were inconsistent. Systolic and diastolic blood pressures during the video game were more highly correlated from year-to-year than were the resting measures. Regression analysis indicated that systolic reactivity was significantly related to subsequent systolic pressure at rest, particularly among Black girls. Diastolic reactivity was associated with subsequent resting diastolic pressure only among White children. Associations between reactivity and future blood pressure were independent of initial resting blood pressure. This study suggests that cardiovascular reactivity to psychological stress may be one important factor in future level of blood pressure and that the increased heart rate reactivity of Black children may be associated with the prevalence of hypertension among Black adults.     

Reporting of life events, family history of hypertension, and cardiovascular activity at rest and during psychological stress

This study investigated whether relations between stressful life events and cardiovascular activity obtained during periods of rest and stress varied as a function of family history of hypertension. Within the family history of hypertension group, males exhibited a positive association between the number of negative avoidable events and resting systolic blood pressure, whereas an inverse association between these two variables was obtained for females. Among females with a family history of hypertension, inverse associations between resting diastolic blood pressure and the subjective effects of life event and number of avoidable events were obtained. Analyses revealed that diastolic blood pressure reactivity to stress was associated with those persons with a family history of hypertension who reported fewer negative life events and less subjective effects for these events.     

Classification of individual differences in cardiovascular responsivity: The contribution of reactor type controlling for race and gender

Classification of 150 normotensive or mildly hypertensive men and women into myocardial, vascular, or mild reactors was accomplished using a regression-based approach. The method was based on the participants’ cardiac output (CO) and total peripheral resistance (TPR) reactivity to the speech presentation task. This task purportedly can elicit both myocardial and vascular responses. Cut-scores were based on the v-intercept from the linear regression of the CO reactivitv on TPR reactivity and vice versa. A greater percentage of Black men were classified as vascular responders as compared to Black women and White participants. Groups were found to differ on cardiovascular reactivity to the speech preparation, cold pressor, and mirror tracing tasks in predictable ways, after controlling for gender and ethnicity. Groups were also differentiated by ambulatory blood pressure and hypertensive status. The study supports the classification of homogeneous groups of participants based on the relative extent to which myocardial or vascular mechanisms dominate the reactivity to stress.     

Cardiovascular recovery from stress predicts longitudinal changes in blood pressure

Cardiovascular reactivity and recovery were examined as predictors of blood pressure changes over 3 years. Blood pressure and heart rate readings were obtained from 73 men and women aged 18-20 years during cold pressor, mental arithmetic, tourniquet ischemia, cycle exercise and step exercise tasks. Regression analyses indicated that after adjustment for initial blood pressure, initial age, initial body-mass index, sex, parental history of hypertension, and length of follow-up, heightened heart rate reactivity to mental arithmetic was associated with increased follow-up systolic blood pressure (DeltaR(2)=0.04, P<0.05). Systolic blood pressure recovery from cold pressor and tourniquet ischemia were also positively related to follow-up systolic blood pressure (DeltaR(2)=0.04 and 0.04, respectively, P<0.05) and remained so even after adjustment for the corresponding cardiovascular reactivity measures. These findings suggest that cardiovascular reactivity and recovery measures are modest predictors of longitudinal changes in blood pressure.     

The effect of systemic blood pressure on cardio-vascular reflexes in elderly subjects.

The evidence for impairment of cardiovascular reflexes by hypertension in elderly subjects is mixed. This study tested the hypothesis that baroreceptor- and non-baroreceptor-mediated responses in elderly subjects differed with hypertension. 54 elderly subjects were studied: 16 with combined hypertension (CT) (blood pressure 184 +/- 4/102 +/- 2 mmHg), 16 with isolated systolic hypertension (180 +/- 3/85 +/- 1 mmHg) and 22 normotensives (NT) (138 +/- 2/76 +/- 1 mmHg). All subjects performed isometric exercise with a handgrip dynamometer. Heart rate (HR), blood pressure and forearm vascular resistance (FVR) responses were then studied to 60 degrees head-up tilt and the cold face stimulus. Baseline FVR, and the response to isometric handgrip, were similar in all groups. Subjects with isolated systolic hypertension manifested greater increases in FVR with tilt (P<0.001), whilst the HR increment was greater in the NT group (P<0.001). Blood pressure changes with tilt were similar in the three groups. With the cold face stimulus (CFS) a rise in FVR of approximately 30% was seen in all groups and blood pressure rose modestly, with the largest increases being seen in the combined hypertensives. This study in elderly subjects indicates significant differences with hypertension in the response to tilt, with an impaired baroreceptor-cardiac reflex being compensated by an augmented baroreceptor-vascular response.     

Serum Lipids,Neuroendocrine, and Cardiovascular Responses to Stress in Men and Women with Mild Hypertension

Abstract

In this study, we examined the relation between serum lipid levels, gender, and cardiovascular and neuroendocrine stress reactivity in patients with mild hypertension. Ninety-nine individuals (62 men, 37 women) with mild hypertension performed four mental stress tasks: mental arithmetic, public speaking, cold stress, and a computer videogame. Cardiovascular reactivity scores were computed by subtracting the minimum resting blood pressure (BP) and heart rate (HR) values from the maximum values obtained during each task. Neuroendocrine reactivity was calculated as the change from epinephrine and norepinephrine values from mean rest to mean task. High and low reactors were identified on the basis of median splits of reactivity scores, averaged across all four stressors. High systolic blood pressure reactors had higher levels of total (TC), low-density lipoprotein cholesterol (LDL-C), and apo-B than did low reactors. High diastolic blood pressure reactors had lower levels of high-density lipoprotein cholesterol (HDL-C) and higher levels of LDL-C and apo-B than did low reactors. High HR reactors had higher apo-AI:apo-AII ratios than low reactors. Lipid levels were not different for high and low epinephrine and norepinephrine reactors. Although women were noted to have more favorable lipid profiles than men, both male and female hypertensive patients who were high reactors had less favorable lipid profiles than low reactors.     

Laboratory stress testing to assess real-life cardiovascular reactivity

Thirty-six normotensive adults received laboratory stress testing (mental arithmetic, short-term memory, isometric handgrip, cold pressor tests) and 24-hour ambulatory blood pressure monitoring on two work days separated by a month. Laboratory and ambulatory measures of cardiovascular reactivity had low test-retest reliability. Increases in blood pressure during the memory and cold pressor tests were related to measures of reactivity obtained outside the laboratory (waking blood pressure variability, responses to home and work environments). However, the portion of ambulatory reactivity accounted for by laboratory reactivity was small. In the best case (r = 0.43), cold pressor diastolic pressure explained only 19% of diastolic pressure variability in the natural environment. Laboratory-ambulatory disagreement in reactivity was related to interindividual variability in physical activity on the day of ambulatory monitoring.     

Neuroendocrine and Cardiovascular Stress Reactivity in Middle-Aged Normotensive Adults with Parental History of Cardiovascular Disease

Neuroendocrine and cardiovascular stress reactivity was studied in healthy middle-aged individuals whose parental history included essential hypertension and/or myocardial infarction and a control group without parental history of cardiovascular disease. All subjects completed a rest session (1 hour) and a stress session (1 hour). The stress session included behavioral (mirror image tracing, mental arithmetic, and the Stroop color word conflict test) and physical stressors (the cold pressor test and isometric exercise). Systolic and diastolic blood pressures and heart rate were recorded at baseline before and during all stressors. Specimens for determination of urinary catecholamines and cortisol were sampled after the rest and stress sessions respectively. Generally, a parental history of hypertension but not of myocardial infarction influenced neuroendocrine and cardiovascular stress reactivity. A family history of hypertension was associated with exaggerated epinephrine, norepinephrine, and cortisol excretion during stress and with enhanced heart-rate reactivity to behavioral (mental arithmetic and mirror image tracing) but not to physical stressors (isometric exercise or the cold pressor test). We conclude that individuals with a family history of hypertension tend to display exaggerated cardiovascular and neuroendocrine reactivity to stress.     

Cardiovascular Effects of Mental Arithmetic in Type A and Type B Females

The cardiovascular responsivity of women demonstrating the Type A coronary-prone behavior pattern was investigated by presenting female Type A and Type B subjects with a challenging mental arithmetic task. Female subjects responded to the task with elevations in heart rate, blood pressure, and forearm blood flow, but did not show the active vasodilatation in the forearm vasculature seen in males in an earlier study. Type A females as a group were not hyperresponsive compared to Type B. However, measures of Type A behavior interacted with family history of hypertension such that, in the subgroup with a positive family history, the Type A behavior pattern was associated with larger cardiovascular responses. The results suggest that sex differences could be present in the expression of the cardiovascular concomitants of Type A behavior. Both gender and family history of cardiovascular disease may represent additional dimensions in the understanding of the pathological mechanisms linking Type A behavior and coronary disease.     

The Relation Between Rhythmic Cardiovascular Variability and Reactivity to Orthostatic, Cognitive, and Cold Pressor Stress

Two groups of normotensive, male subjects having either a positive or negative parental history of essential hypertension were exposed to passive body tilt from horizontal to a 70° head-up posture, while systolic and diastolic blood pressure, heart period, and respiration amplitude were sampled on a beat-by-beat basis. Subjects also performed mental arithmetic and cold pressor tasks, and cardiovascular reactivity was expressed as change from baseline levels. The body tilt data were analyzed by cross-spectral analysis focusing on two frequency bands, one between .06-.1 Hz, and the other at the predominant breathing frequency. The two groups did not differ significantly in their basal levels of physiological activity or in their response to the tasks. Cross-spectral analysis identified tilt induced changes in the power spectra and coherence spectra within the two frequency bands. These changes differed between the two frequency bands and among the various physiological response systems investigated. Larger rhythmic oscillations in heart period within both frequency bands predicted greater cardiovascular reactivity to the mental arithmetic task but not the cold pressor task. The results are discussed in terms of neural control mechanisms (e.g., vagal tone) implicated in the dynamic regulation of cardiovascular function during psychophysiological states such as stress.     

Hemodynamic profile of stress-induced anticipation and recovery.

Systolic and diastolic blood pressure, heart rate, stroke volume, cardiac output, and total peripheral resistance were measured in 100 healthy men and women with the aim of investigating hemodynamic profile during anticipation of, and recovery from, exposure to active and passive laboratory stressors. A 5-min anticipatory period preceded two tasks, both of which lasted 2.5 min. The tasks were mental arithmetic ('beta-adrenergic' stress) and the cold pressor test ('alpha-adrenergic' stress). Each task was followed by a 5-min recovery period. Blood pressure and heart rate were measured with a FinaPres 2300e, and stroke volume, cardiac output, and total peripheral resistance were computed from these parameters. Salivary cortisol was measured in relation to both tasks, and participants completed tests of state and trait anxiety, locus of control, and hostility. As expected, mental arithmetic and the cold pressor test elicited myocardial and vascular patterns of reactivity, respectively. However, contrary to expectations, anticipatory and recovery hemodynamic profile involved essentially vascular responding for both stressors. Salivary cortisol increased in response to both tasks but only weakly correlated with hemodynamic changes. None of the subjective measurements was a strong predictor of physiological reactivity. The findings suggest that stress-induced anticipatory and recovery reactivity may be generally vascular rather than myocardial. This could have important implications in light of suggestions that anticipatory and recovery responses may be better predictors of subsequent cardiovascular disease than direct stress-induced reactivity.     

Blood pressure and muscle sympathetic nerve activity during cold pressor stress: fitness and gender

We examined putative autonomic and hemodynamic mechanisms that might explain our prior finding that cardiorespiratory fitness mitigates blood pressure responses by normotensive women during the hand cold pressor test. We report that fitness level was inversely related to increases in systolic and diastolic blood pressures and muscle sympathetic nerve activity (MSNA) during the cold pressor among women but not men. The pattern of responses among fitter women was consistent with decreased central sympathetic outflow resulting in reduced stroke volume or dampened peripheral resistance in vascular beds other than calf skeletal muscle. Fitter men and women had slightly larger increases in blood pressure during mental arithmetic, but otherwise fitness was not directly related to stress responses. The results further encourage consideration of cardiorespiratory fitness as a modifying covariate when the hand cold pressor test is used as a predictor of future hypertension among women.     

Effects of anger/hostility, defensiveness, gender, and family history of hypertension on cardiovascular reactivity

In this study, we examined the combined effects of anger/hostility and defensiveness on reactivity to three stressors (math, handgrip, cold pressor) and how these effects are moderated by gender and family history of hypertension. The subjects were 209 college students. Low compared with high Spielberger anger-out scores were associated with greater diastolic blood pressure (DBP) reactivity in low-but not high-defensive women with a negative family history. High compared with low hostility scores were associated with greater heart rate reactivity in low-defensive men with an opposite effect in high-defensive men. Gender, family history, and defensiveness each affected differential DBP reactivity to the three tasks. Combined study of biological factors and coping styles can improve our understanding of cardiovascular reactivity and disease.     

Alpha-adrenergic receptor gene polymorphisms and cardiovascular reactivity to stress in Black adolescents and young adults

Cardiovascular reactivity to stress and α-adrenergic receptor (α-AR) function may contribute to the development of hypertension. As Black Americans have an increased risk of hypertension, we evaluated associations between α(1A) -AR (Arg492Cys), α(2A) -AR (-1291C/G), and α(2B) -AR (Ins/Del301-303) gene variants and cardiovascular reactivity in 500 normotensive Black youth. Heart rate, preejection period, total peripheral resistance, and blood pressure were measured during cold and psychological stress. The Arg492Cys polymorphism in the α(1A) -AR gene was associated with heart rate reactivity to stress, but the association depended on sex. The -1291C/G promoter polymorphism in the α(2A) -AR gene was associated with vascular reactivity to stress; vasoconstriction increased as a linear function of the number of copies of the variant G allele. Thus, specific associations emerged between genetic variations in α-Ars and cardiovascular reactivity in young Blacks.     

Cardiovascular responses to psychological and physiological stressors during the menstrual cycle

Psychological and physical stress reactivity was studied in 15 females in two phases of the menstrual cycle (cycle days 5-7 and 24-26) and in 15 males. Each female was matched for age and time between sessions with a male. There was a significant phase-related difference in cardiovascular reactivity among the females. Females in the luteal phase reacted significantly more to the cold pressor but not to the mental arithmetic test. There were significant sex differences in systolic blood pressure, the males displaying higher levels during provocation, as well as during control conditions. The females were more reactive in heart rate to the mental stressor when changes from control conditions to stress were calculated. When the data were analyzed separately for smokers and non-smokers, there was a significant interaction between menstrual cycle phase and smoking. In the luteal phase, the female smokers were more reactive in systolic blood pressure than the non-smokers. The male smokers were more reactive than the non-smokers in diastolic blood pressure response to mental arithmetic, but not to the cold pressor test. Significantly higher levels of cortisol and aldosterone were found in the luteal phase as compared with the follicular phase. The cortisol levels were higher in the males than in the females in the follicular phase, whereas the female aldosterone concentrations in the luteal phase were higher than those of the males.     

Caffeine Affects Cardiovascular Responses to Stress

The effects of caffeine on cardiovascular activity at rest and during psychological stress were examined in 33 healthy male college students who did not normally ingest caffeinated products. Caffeine (250 mg) and placebo were administered double-blind in separate sessions. Heart rate, blood pressure, and forearm blood flow and vascular resistance were assessed at rest and during the stressful, competitive performance of a mental arithmetic task. Comparisons of caffeine and placebo sessions revealed that caffeine elevated resting blood pressure 4–6 mmHg, an effect which added to the elevation produced by stress. Caffeine did not affect resting forearm blood flow but potentiated the forearm blood flow response to stress and led to higher levels of flow during stress. No caffeine effects appeared in heart rate or in task performance. Family history of hypertension and Type A behavior were examined as potential modulating factors of caffeine effects but results were generally negative. These results suggest possible mechanisms through which caffeine could enhance the pathogenic effects of stress on the cardiovascular system.     

Menopause induced by oophorectomy reveals a role of ovarian estrogen on the maintenance of pressure homeostasis

OBJECTIVES: Following spontaneous menopause women show a greater increase in systolic and diastolic blood pressure than men of the same age. The aim of the present study was to assess the effect of acute ovarian hormone withdrawal and replacement on blood pressure and forearm blood flow. METHODS: We studied 18 fertile middle-aged normotensive women (48 +/- 1.5 years, range 46-51 years) 1 week prior and 1 month subsequent to bilateral oophorectomy by means of 24-h blood pressure monitoring and strain-gauge venous occlusion plethysmography. Eighteen subjects who had undergone hysterectomy with ovarian sparing, matched for age and biophysical characteristics, were used as a control group. All women were free from cardiovascular risk factors or disease. RESULTS: Oophorectomy increased the mean values of 24 h (P < 0.001), daytime (P < 0.05), and nighttime (P < 0.01) diastolic blood pressure and nighttime systolic blood pressure (P < 0.01). Blood pressure increase was associated with a rise in forearm vascular resistance (P < 0.01). No significant changes in either blood pressure or forearm vascular resistance values were observed in hysterectomized women. In 16 oophorectomized women a 3-month estrogen replacement therapy (ERT) (17beta-estradiol, 100 mcg/day by transdermal patches) brought blood pressure and forearm vascular resistance values to a level comparable to that recorded before intervention. CONCLUSIONS: Surgically-induced menopause causes an increase in peripheral vascular resistance and blood pressure suggesting a role of ovarian hormones in the homeostatic pressure modulation. Recovery of the baseline condition after ERT suggests that the accelerated increase in blood pressure after menopause is due to ovarian and above all estrogen insufficiency.