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.     

Hemodynamic response patterns: responder type differences in reactivity and recovery

We examined whether responder type groups reflecting patterns of hemodynamic reactivity might also differ in recovery responses. Cardiac output (CO), total peripheral resistance (TPR), systolic and diastolic blood pressure, heart rate, and Heather index were assessed at rest and during speech and cold pressor tasks in young adults. Participants (n = 152) were classified as myocardial, vascular, or mixed-mild responders based on CO and TPR responses to speech presentation. Vascular responders exhibited slower CO and TPR speech recovery than the myocardial and/or mixed-mild groups. Responder type differences in reactivity showed limited task-generalizability. The sustained vascular response pattern of the vascular group is consistent with that seen in hypertension. In light of associations of heightened TPR with markers of disease risk, this suggests potentially negative health implications for vascular responders.     

The relationships of impulsivity and cardiovascular responses: The role of gender and task type

The present study was conducted to assess the relationships of impulsivity with both baseline cardiovascular levels and reactivity during two laboratory stressors in both female and male young adults. Heart rate (HR), blood pressure (BP), and heart rate variability (HRV) were measured at rest and during a reaction time and speech task in one hundred and one undergraduate students. Impulsivity was measured using the Barratt Impulsiveness Scale-11 and Block's Ego-Undercontrol Scale. Males and females responded similarly to both laboratory tasks and also did not differ on the impulsivity scales. For males, higher scores on impulsivity were associated with higher systolic BP levels at rest but decreased systolic BP and HR reactivity during the preparation of the speech task; females showed no relationships of resting cardiovascular levels with impulsivity, but more impulsive females did show decreased HR response during speech preparation. No significant relationships were found between impulsivity and either HRV levels or reactivity. It is speculated that tasks involving a degree of planning may be important to find relationships between impulsivity and cardiovascular reactivity, especially in males.     

Cardiovascular Responses to Stress: I. Measures of Myocardial Response and Relationship to High Resting Systolic Pressure and Parental Hypertension

A comparison of pre-ejection period (PEP), heart rate (HR), and systolic (SBP) and diastolk (DBP) blood pressure responses to the cold pressor test and a pseudo-shock avoidance reaction time task was performed in 183 young men. These tasks differ in the extent to which they evoke enhanced myocardial and vascular adrenergic activity. Decreases in PEP were more pronounced during the reaction time task, while DBP increased more during the cold pressor test. MR and SBP responses did not differentiate the two tasks. PEP decreases occurred in the absence of any apparent increase in cardiac preload or decrease in afterload. Parental hypertension as determined by physician reports was associated with higher SBP across all conditions. A subgroup of individuals (15%) showed SBP levels >140 mm Hg when typical clinical stethoscopic determinations were made, but less than half as many showed such elevations during a more extended resting baseline using remotely operated devices. High stethoscopic SBP was associated with greater cardiovascular responses to the stressors, while high SBP during the extended baseline was not.     

Myocardial and Peripheral Vascular Responses to Behavioral Challenges and Their Stability in Black and White Americans

The purpose of this study was to assess the short term stability of myocardial and peripheral vascular responses to behavioral challenges, and to compare the response patterns of Black and White men. Blood pressure and heart rate, as well as stroke volume, cardiac output, total peripheral resistance, and systolic time interval measures derived from the impedance cardiogram were obtained in 12 Black and 12 White men. These measures were taken prior to and during an evaluative speech stressor, a mirror star tracing task, and a forehead cold pressor test presented during two laboratory sessions scheduled two weeks apart. In general, total peripheral resistance and impedance-derived baseline measures showed acceptable reproducibility (G greater than .85). With a few exceptions, adequate reliability was also demonstrated for change (delta) scores. All tasks raised blood pressure responses above resting levels. Blacks demonstrated significantly greater increases in total peripheral resistance responses across tasks. Whites but not Blacks also revealed increases above baseline in cardiac output and contractility as estimated by the Heather Index. These findings are consistent with the view that Blacks show greater vascular responsiveness than Whites across a variety of tasks, but reveal less myocardial responsiveness.     

Plasma oxytocin is related to lower cardiovascular and sympathetic reactivity to stress

In addition to known reproductive and social affiliation functions, oxytocin (OT) has been identified as a cardiovascular hormone. OT synthesis and receptors are found in cardiac and vascular tissue. Animal studies suggest that OT activates an ‘anti-stress’ response that reduces cardiovascular and neuroendocrine stress reactivity. We tested 28 early postpartum mothers, obtaining multiple blood samples for OT, the sympathetic marker, norepinephrine (NE), and the lactation hormone, prolactin, while monitoring their cardiovascular responses to two stressors: public speaking and forehead cold pressor. Although plasma OT did not increase reliably from pre-stress levels during stressors, greater overall OT level was related to greater vasodilation and cardiac stroke volume responses to both tasks, to reduction in heart rate to the cold pressor, as well as to lower plasma NE and higher prolactin levels. In contrast, higher NE was linked to increases in heart rate and decreases in stroke volume. These data support a cardioprotective role for OT, which may influence the magnitude and hemodynamic determinants of cardiovascular stress responses.     

Cardiovascular and sympathoadrenal responses to mental stress: a study of sensory intake and rejection reactions

Cardiovascular, sympathoadrenal and subjective responses to mental stress induced by two mental challenges eliciting sensory intake (word identification test = WIT) and sensory rejection (colour word conflict test = CWT) reactions were studied in 10 healthy males. Pressor responses to these stressors have been proposed to differ haemodynamically. Sympathoadrenal activity was assessed by arterial and femoral venous plasma catecholamine determinations and direct recordings of muscle sympathetic activity in the right peroneal nerve (MSA). Basal measurements differed little from those made during an active relaxation procedure, with the exception of MSA, which decreased. Both stress tasks elicited increases in heart rate, cardiac output, calf blood flow and brachial and pulmonary arterial blood pressures. WIT and CWT elicited qualitatively similar responses, but the amplitudes of the circulatory responses were lower with WIT, which also was rated as a weaker stressor. MSA increased during CWT, while marginal increases were seen during WIT. Arterial adrenaline showed a transient increase by 0.14 nmol l-1 during WIT. During CWT arterial adrenaline increased significantly by 50%. Increases in arterial adrenaline and subjective stress ratings were related to increases in cardiac output and reductions of systemic vascular resistance. Arterial and femoral venous noradrenaline increased during CWT, while changes during WIT were small. MSA and noradrenaline responses did not correlate to local vascular responses in the calf. Differences in the responses to mental challenges evoking sensory intake or rejection seem to be of a quantitative rather than a qualitative character.     

Reproducibility of blood pressure and heart rate reactivity: A meta-analysis

Reproducibilities of blood pressure and heart rule (HR) reactivity reported in studies assessing responses to the same laboratory stressors across occasions were reviewed with meta-analytic techniques. Changes in HR had the greatest reproducibility (r =.555), followed by systolic blood pressure (SBP) (.407) and diastolic blood pressure (DBF) (.348), Both SBP and HR response reproducibility was higher at shorter lest-retest intervals, whereas DBP values varied unsystematically with length of test-retest interval Older samples exhibited higher SBP and DBP reproducibility to stressors. SBP and DBP reproducibilities were better for tasks that did not make speech demands. The reliability of reactivity assessment was higher when based on three or more measurements, On the basis of able evidence, the drop in stress reproducibility, as test-retest interval increases, places limits on the viability of BP reactivity as a strong marker or risk factor for coronary heart disease.     

Breast-feeding and maternal cardiovascular function

Two studies examined the effects of breast-feeding on maternal cardiovascular function. In the first experiment, groups of breast-feeding and bottle-feeding women were compared on preejection period (PEP), heart rate (HR), cardiac output (CO), and total peripheral resistance (TPR) recorded for 1-min periods before and during standard laboratory stressors. Compared with bottle-feeders, breast-feeders had higher CO throughout the session, and greater decreases in CO and increases in TPR during cold pressor. In the second experiment, HR and blood pressure (BP) were compared before and after one breast-feeding and one bottle-feeding session in a within-subjects design. Both feeding methods increased BP but decreased HR, and systolic BP was higher for the breast-feeding than the bottle-feeding condition. Both studies support the notion that breast-feeding alters maternal cardiovascular function, possibly through the actions of oxytocin.     

Behaviorally-evoked plasma catecholamine response and 24-hour excretion of urinary catecholamines among cardiac and vascular reactors

Individuals differ in the cardiac and vascular processes that underlie blood pressure elevations evoked by environmental stimuli; such differences may reflect variability in sympathoadrenal response. We separated 108 healthy, young-adult males into those with predominant elevations in either cardiac output or peripheral resistance when exposed to psychological challenges. We then asked if they differed on other measures of cardiovascular response, concomitant plasma catecholamine reactions or 24-h urinary excretion of catecholamines. Cardiac reactors, relative to vascular reactors, showed reduced cardiac pre-ejection period, a smaller reduction in stroke volume, and elevated plasma epinephrine response and 24-h urinary epinephrine excretion. Vascular reactors, relative to cardiac reactors, responded to mental stress with more elevated diastolic blood pressure, a rise in peripheral resistance and pulse wave velocity, and a greater reduction in stroke volume. Vascular reactors, however, did not show plasma norepinephrine response or 24-h urinary norepinephrine excretion that was greater than cardiac reactors. The results provide partial support for the hypothesis that variability in sympathoadrenal activity contributes to individual differences in cardiac and vascular reactivity, and extend prior observations by demonstrating covariation of behaviorally-elicited cardiac reactivity with the 24-h excretion of epinephrine.     

Individual Differences in Behaviorally Evoked Cardiovascular Response: Temporal Stability and Hemodynamic Patterning

This study evaluates the reproducibility of individual differences in behaviorally evoked cardiovascular reactivity among 39 young adult males. Presented also are initial data describing idiosyncratic patterns of hemodynamic adjustment that may underlie pressor responses to laboratory stressors. Subjects were administered three experimental stressors (mental arithmetic, mirror tracing, and bicycle exercise) on two occasions, four weeks apart. Heart rate, blood pressure, and impedance-derived measurements of cardiac pre-ejection period, stroke index, cardiac index, and total peripheral resistance were obtained during baseline and task periods at each session. To index task-induced "reactivity," residualized (baseline-adjusted) change scores were calculated for all variables; percentage change from baseline was also calculated for impedance-derived hemodynamic measurements. Test-retest (inter-session) correlations were significant for nearly all baseline, task, and change-score measurements. The few exceptions included diastolic blood pressure changes during mirror tracing and bicycle exercise and changes in stroke index and peripheral resistance during mental arithmetic. Although virtually all baseline and task correlations exceeded .60, reactivity indices yielded consistently lower retest correlations (significant r's = .35-.78; median r = .49). In subsequent analyses, subsets of individuals were identified whose reactions to mental arithmetic at the first laboratory session reflected changes in either cardiac output (CI reactors, n = 9) or total peripheral resistance (TPR reactors, n = 6), or a combination of cardiac and vascular influences (Mixed reactors, n = 8). This typology of hemodynamic response: (a) was corroborated by corresponding group differences in heart rate, pre-ejection period, and stroke index; (b) was reproducible on retesting; and (c) showed some generalization to the mirror tracing task, though not to bicycle exercise.     

Mechanisms underlying hemodynamic and neuroendocrine stress reactivity at different phases of the menstrual cycle

This study examined the association of menstrual cycle phase with stress reactivity as well as the hormonal and neuroendocrine mechanisms contributing to cycle effects. Fifty‐seven women underwent a modified Trier Social Stress Test during the early follicular, late follicular, and luteal phases of the menstrual cycle. Greater increases in cardiac index (CI) and greater decreases in vascular resistance index (VRI) during speech were observed in the luteal phase relative to other phases, while greater increases in epinephrine (EPI) was observed during the late follicular and luteal phases compared to the early follicular phase. Luteal phase estradiol predicted luteal EPI reactivity but not CI or VRI reactivity, while luteal phase EPI reactivity predicted luteal phase CI and VRI reactivity. Thus, cycle‐related changes in EPI reactivity may be a stronger determinant of cycle effects on hemodynamic reactivity than sex hormones per se.     

Gender differences in blood pressure control during a variety of behavioral stressors

This study assessed gender differences in hemodynamic response patterns to behavioral stressors. In addition, the extent to which gender differences in cardiovascular reactivity were a function of the type of challenge was determined by employing tasks relying on stereotypically male areas of competence and a task relying on stereotypically female areas of competence. Sixteen female and 15 male graduate, medical or dental students were exposed to two speech tasks and two math tasks. While there were no significant differences in blood pressure reactivity between the genders, females exhibited significantly greater cardiac output increases across all tasks than males, while males tended to respond with greater increases in total peripheral resistance compared with females. Furthermore, during two of the tasks, significantly more females were classified as myocardial hyperreactors (based on increases in cardiac output), while significantly more males were vascular hyperreactors (based on increases in total peripheral resistance). A post hoc analysis also indicated an apparent association between oral contraceptive use and higher cardiovascular reactivity among the females tested. This association may have been a consequence of the decision to test all women during days 10 to 14 of the menstrual cycle when reactivity in women not using oral contraceptives may be suppressed.     

Differential hostility profiles accompany different hemodynamic response patterns

Cardiovascular reactivity has been proposed as a mechanism by which psychosocial variables may lead lo coronary heart disease. Although reactivity as a generalized response has been linked lo psychological factors, there are specific hemodynamic profiles that underlie blood pressure reactivity. This study characterized subsets of young adults as myocardial or vascular reactors, in response to three laboratory tasks: mental arithmetic, videogame, and anger recall interview. Vascular reactors had higher diastolic blood pressure increases to all tasks, whereas reactor groups were equivalent at rest and on systolic blood pressure responses. Correlational analyses were conducted to determine whether psychological dimensions are uniquely associated with myocardial or vascular reactors' cardiovascular responses, at rest and during acute stressors. For myocardial reactors, resting systolic blood pressure was higher in hostile and suspicious individuals, whereas reactivity was linked to impulsivity. For vascular reactors, low trust, low gregariousness, and high depression were associated with diastolic reactivity to tasks. The predictive validity of hostility, distrust, sociability, and depression for cardiovascular pathology may vary with reactor type.     

Cardiovascular reactivity to stress in black male offspring of hypertensive parents

The forearm blood flow (FABF) and other cardiovascular responses of 20 black men with a parental history of hypertension were compared with the responses of 18 black men without a parental history of hypertension. The results showed that sons of hypertensive parents had higher systolic (SBP) and diastolic (DBP) blood pressure than sons of normotensive parents during the initial assessment as well as significantly higher self-determined home SBP. Sons of hypertensive parents had higher SBP responses than sons of normotensive parents during mental challenge and the cold pressor, but there were no group differences in DBP, heart rate (HR), (FABF), or forearm vascular resistance (FAVR) responses to the stressors. Significant positive correlations between HR and FABF responses to the stressors were observed for sons of hypertensive parents. Finally, the results showed that the BP and FAVR responses to the cold pressor (a painful task that elicits alpha-adrenergic activity) were significantly higher than responses to mental challenge (a task that elicits beta-adrenergic activity) for both groups. The implications of these results are discussed in light of current research suggesting that blacks may have a greater tendency toward BP responses mediated by alpha-adrenergic increases in vascular resistance.     

Reactivity and vulnerability to stress-associated risk for upper respiratory illness

OBJECTIVE: We tested the hypothesis that the greater a person's laboratory stress-elicited elevation in cortisol, the greater the life stress-related risk for upper respiratory infection (URI). We also tested the prediction that the greater the laboratory stress-elicited rise in natural killer cell (NK) cytotoxicity, the smaller the life stress-related URI risk. Finally, we explored whether sympathetic nervous system (SNS) and enumerative immune reactivities to laboratory stress moderate the relation between life stress and URI. METHODS: At baseline, 115 healthy subjects were administered a negative stressful life events checklist and were tested to assess their SNS (blood pressure, heart rate, and catecholamines), HPA (cortisol), and immune (NK cell cytotoxicity and lymphocyte subsets) reactivities to laboratory speech tasks administered 2 weeks apart. Responses were averaged across the two laboratory assessments to create reactivity scores. After these assessments were completed, participants were followed weekly for 12 consecutive weeks. At each follow-up they completed a measure of perceived stress experienced over the last week. They were also instructed to contact the study coordinator if they had a cold or flu at any time during follow-up. A health care worker verified reported illnesses. RESULTS: In a traditional prospective analysis, high cortisol reactors with high levels of life events had a greater incidence of verified URI than did high reactors with low levels of life events and low reactors irrespective of their life event scores. Using hierarchical linear modeling, CD8(+) number, Natural Killer (NK) cell number, and NK cell cytotoxicity, each interacted with weekly perceived stress levels in predicting concurrent occurrences of self-reported URIs. For these outcomes, low immune reactors were more likely to experience an URI during high stress than low stress weeks. High immune reactors did not exhibit differences in weekly URIs as a function of weekly stress level. The SNS reactivity markers did not moderate the association of stress and URI incidence in either analysis. CONCLUSIONS: Acute HPA and immune responses to laboratory stressors are markers of how vulnerable people are to the increased risk for URI associated with stressors in the natural environment.     

Generalization of cardiovascular response: supportive evidence for the reactivity hypothesis.

Cardiovascular responses were monitored while 36 subjects completed a battery of laboratory stressors comprising mental arithmetic, a reaction time task, a speech task, and the forehead cold pressor. Inter-task consistency was assessed for each of 6 physiological parameters for all task pairings. Considerable inter-task consistency for reactivity scores was seen among the psychological stressors for all variables. The question of such consistency between the cold pressor and the psychological tasks was then addressed. The pattern of consistency was not as clear-cut in this case. For systolic blood pressure and pre-ejection period, reactivity scores to the cold pressor did not correlate with those to any of the psychological tasks. In contrast, cardiac output and total peripheral resistance responses showed considerable consistency. The importance of determining the nature of the relationship between psychological and physical stressors is discussed.     

Frontal electrocortical and cardiovascular reactivity during happiness and anger

The present study investigated electrocortical and cardiovascular reactivity during positive and negative emotion, and examined the relation of asymmetric frontal lobe activation to cardiovascular responses. Participants were 30 healthy, right-handed university students (mean age, 23.9; 60% female; 76% Caucasian). Electroencephalographic (EEG), blood pressure (BP), and heart rate (HR) responses were assessed while subjects engaged in laboratory tasks (personally-relevant recall tasks and film clips) designed to elicit happiness or anger. Happiness-inducing tasks evoked more prominent left than right frontal EEG activation, and greater left frontal EEG activation than anger-inducing tasks. However, anger-inducing tasks were, on average, associated with comparable left and right frontal EEG activation. Irrespective of emotional valence, cardiovascular activation was more pronounced during personally-relevant recall tasks than during the viewing of film clips. During anger recall, both greater left frontal EEG response (r=-0.46, P<0.02) and greater right frontal EEG response (r=-0.45, P<0.02) were correlated significantly with increased HR reactivity during the task. In addition, a right lateralized frontal EEG response during anger-inducing tasks was associated with greater concomitant systolic BP (P<0.03) and diastolic BP (P<0.008) reactivity. Exploratory analyses also indicated that men who displayed a left lateralized frontal EEG response during happiness-inducing tasks showed the greatest concomitant systolic BP and HR reactivity (P's<0.03). These findings suggest that asymmetric frontal EEG responses to emotional arousal may elicit different patterns of cardiovascular reactivity in healthy adults.     

Task Difficulty, Heart Rate Reactivity, and Cardiovascular Responses to an Appetitive Reaction Time Task

Cardiovascular responses of 72 young men were assessed during an appetitive reaction time task where winning money incentives was either easy, difficult, or impossible. The impossible condition led to reduced responses (e.g., longer pre-ejection period (PEP) and pulse transit time (PTT) and greater falls in systolic and diastolic pressures) as well as reports of trying less hard than the easy or the difficult condition. Regardless of task difficulty, subjects showing greater heart rate (HR) increases at task onset maintained higher HR levels than low HR reactors throughout the task. Overall, these high HR reactors also showed higher SBP and shorter PEP, PTT and left ventricular ejection time than low HR reactors, although these differences were less pronounced by the end of the task. Based on their responses to various standardized inventories, high and low HR reactors did not differ in behavioral traits such as Type A, suppressed hostility, or active coping as the preferred coping style. However, a subsample of subjects with extreme scores indicating suppressed hostility (N = 12) did show elevated HR and systolic pressure during both relaxation and the appetitive task.