Hemodynamic responses during psychological stress: Implications for studying disease processes

Effects of Psychological Stress on Vascular Physiology: Beyond the Current Imaging Signal

PURPOSE OF REVIEW

This review describes the effects of psychological stress on the physiology of the entire vascular system, from individual cellular components to macrovascular and microvascular responses, and highlights the importance of the vascular system in the context of current limitations in cardiac imaging for evaluation of the cardiovascular response to mental stress.

RECENT FINDINGS

The physiological responses that mediate vascular changes are based on evolutionary needs, but there is increasing evidence that the long-term consequences of psychological stress can precipitate the development and progression of cardiovascular disease (CVD). While there is an extensive body of literature describing localized physiological responses or overt cardiovascular manifestations, often framed within the organ-specific scope of cardiovascular imaging, there has not been a comprehensive description of the global vascular effects of psychological stress. Given the global nature of these processes, targeted cardiovascular imaging modalities may be insufficient. Here we approach the vascular response to mental stress systematically, describing the effects on the endothelium, vascular smooth muscle, and adventitia. We then address the mental stress effects on large vessels and the microvascular compartment, with a discussion of the role of microvascular resistance in the pathophysiology of mental stress-induced myocardial ischemia. Vascular responses to psychological stress involve complex physiological processes that are not fully characterized by routine cardiovascular imaging assessments. Future research incorporating standardized psychological assessments targeted toward vascular mechanisms of stress responses is required to guide the development of behavioral and therapeutic interventions.

Perceived Racism and Ambulatory Blood Pressure in African American College Students

Experiences with racial discrimination may contribute to stress-induced blood pressure (BP) elevations among African Americans. It was reported that perceived racism was associated with ambulatory BP (ABP) during waking hours. This study examined perceived racism and ABP among 40 African American college students, who completed an ABP assessment from which daytime and nighttime averages were computed. Perceived frequency of experiences with racism and racial discrimination was measured using the Perceived Racism Scale. Controlling for gender and body mass index, perceived racism in academic settings was associated with higher diastolic BP (DBP) during waking hours and nighttime sleep. Systolic BP (SBP) was unrelated to perceived racism, and perceived racism in the public realm and in statements from Whites was unrelated to ABP. Perceived racism in academic settings predicted ambulatory DBP among college students. Previous laboratory research has found stronger effects of perceived racism for DBP than SBP. The hemodynamic regulation of BP may explain this phenomenon. Future laboratory and ambulatory studies should assess the contributions of vascular resistance and cardiac output to BP elevations associated with perceived racism.

Older adults' hemodynamic responses to an acute emotional stressor: short report

BACKGROUND/STUDY CONTEXT: Vascular and myocardial activation can each increase blood pressure responses to stressors, but vascular responses are uniquely associated with negative affect, pernicious coping processes, and cardiovascular risk. These hemodynamic correlates of coping in response to acute stressors have not been well characterized in older adults.

METHODS

Adults 65 to 97 years of age (N = 74) either engaged in written disclosure about a distressing event (acute stressor) or wrote objectively about a neutral topic (control). Blood pressure, impedance cardiography, and affect measures were assessed at baseline and in response to writing. Moderating effects of age on affect, blood pressure, and vascular and myocardial responses to the acute stressor were tested using multiple linear regression models.

RESULTS

Follow-up tests of Age × Writing Group interactions indicated that the expected effects of written disclosure on systolic and diastolic blood pressure responses were diminished with increasing age. Regardless of age, compared with neutral writing, written disclosure increased negative affect and vascular responses, but not myocardial responses.

CONCLUSION

Blood pressure responses to an acute, emotionally evocative stressor were indistinguishable from blood pressure responses to a control condition among the eldest older adults in our sample. In contrast, characterizing the hemodynamic mechanisms of blood pressure responses revealed notable vascular effects of the acute, emotional stressor across a wide age range. Such characterization may be particularly useful for clarifying the psychophysiological pathways to older adults' cardiovascular health.

Excess heart rate and systolic blood pressure during psychological stress in relation to metabolic demand in adolescents

Cardiovascular responses during exercise are matched to the increased metabolic demand, but this may not be the case during psychological stress. No studies to date have tested this hypothesis in youth. Fifty-four youth, ages 13-16 years completed two visits. Heart rate (HR), systolic blood pressure (SBP), and oxygen (O(2)) consumption were measured during a graded exercise test on one day and during psychological stress reactivity (star tracing, speech) on another day. Predicted HR and SBP values during psychological stress were calculated based on HR-O(2) and SBP-O(2) relationships calculated during graded exercise. At a given O(2) consumption, actual HR was greater (p<0.02) than predicted for all stress tasks. Actual SBP was greater (p<0.001) than predicted for all stress tasks. This was the first study to demonstrate that cardiovascular responses were in excess of what would be expected based on metabolic demand in youth.

Stress-induced cardiovascular reactivity and atherogenesis in adolescents

OBJECTIVE

To examine the association between cardiovascular reactivity to a set of psychological stressors and carotid artery intima-media thickness, a marker of subclinical cardiovascular disease in healthy adolescents.

METHODS

Participants were 25 boys and 23 girls age 14.2 ± 0.9 years who were measured for heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressure reactivity to mirror-tracing, reaction time, speech preparation and ad lib speech tasks and for common carotid artery intima-media thickness. Sequential regression analyses were used to establish the incremental increase in R(2)(R(inc)(2)) for the prediction of intima-media thickness due to cardiovascular reactivity independent of age, BMI percentile, sex, socioeconomic status, and resting HR or BP.

RESULTS

SBP reactivity while preparing (β=0.0019, R(inc)(2)=0.09) and giving the speech (β=0.0014, R(inc)(2)=0.10) and an aggregate reactivity score based on all 4 tasks (β=0.0026, R(inc)(2)=0.11) independently predicted (p ≤ 0.05) mean carotid artery intima-media thickness. Neither DBP reactivity nor HR reactivity during any task were independent predictors of intima-media thickness.

CONCLUSION

Stress-induced cardiovascular reactivity, and especially SBP reactivity, is associated with carotid intima-media thickness and the early pathogenesis of cardiovascular disease. The use of an aggregate stress reactivity index provides a more reliable reflection of trait SBP reactivity to psychological stress and increases the confidence that youth with greater cardiovascular stress reactivity may indeed have greater progression of subclinical cardiovascular disease.

Appraisal predicts hemodynamic reactivity in a naturalistic stressor

Prior research has shown that appraisals are predictive of hemodynamic reaction patterns. The current study examined the relationship between appraisal and hemodynamic responding in a real-life stressful situation. Twenty-four men aged 19-28 wore a blood pressure monitor while presenting a paper in a class. Participant's appraisal self-reports were obtained prior to the stressor. Multilevel regression models were used to analyze the relationships between appraisal and myocardial responding (as measured by cardiac output) and vascular resistance (as measured by TPR). Pre-stressor appraisals were significantly associated with CO, both during the stressor (Z=2.03 p<.05) as well as during the 30-minute anticipation period preceding the stressor (Z=2.43 p<.01). In line with the predictions, relatively challenged participants showed higher CO. Pre-stressor appraisals significantly predicted TPR during anticipation (Z=2.70 p<.01) but these associations failed to reach significance during the stressor (Z=1.82, n.s.). As was predicted, during anticipation, increased threat was associated with increased TPR. Thus, during the anticipation period prior to the stressor, increased challenge was associated with decreased vascular resistance and increased myocardial reactivity. Further, increased threat was associated with increased vascular resistance and decreased myocardial reactivity. During the stressor increases in challenge were associated with further increases in myocardial responding but relationships between appraisal and vascular resistance were not significant. The current study shows that the relationship between appraisal and hemodynamic reactivity seen in laboratory studies are also present during naturally occurring stress. Our findings suggest that threat appraisals to naturalistic stressors contribute to an, arguably unhealthy, vascular reaction pattern.

Prognosis after change in left ventricular ejection fraction during mental stress testing in patients with stable coronary artery disease

Previous studies of patients with stable coronary artery disease have demonstrated that decreases in the left ventricular ejection fraction (LVEF) during acute mental stress are predictive of adverse clinical outcomes. The aim of the present study was to examine the prospective relation of mental stress on clinical outcomes in a sample of 138 patients with stable coronary artery disease. Patients underwent mental stress testing and were followed for a median of 5.9 years to assess the occurrence of the combined end point of myocardial infarction or all-cause mortality. There were 32 events (17 nonfatal myocardial infarctions and 15 deaths) over the follow-up period. Of the 26 patients who exhibited myocardial ischemia during mental stress testing, 11 (42%) sustained subsequent clinical events, compared to 21 of the 112 patients (19%) who showed no mental stress-induced ischemia. LVEF change during mental stress was also related to the clinical events in a graded, continuous fashion, with each 4% decrease from the LVEF at rest associated with an adjusted hazard ratio of 1.7, (95% confidence interval 1.1 to 2.6, p = 0.011). In conclusion, reductions in the LVEF during mental stress are prospectively associated with adverse clinical outcomes.

Genetic influences on cardiovascular stress reactivity

Individual differences in the cardiovascular response to stress play a central role in the reactivity hypothesis linking frequent exposure to psychosocial stress to adverse outcomes in cardiovascular health. To assess the importance of genetic factors, a meta-analysis was performed on all published twin studies that assessed heart rate (HR) or blood pressure (BP) reactivity to the cold pressor test or various mental stress tasks. For reactivity to mental stress, the pooled heritability estimate ranged from 0.26 to 0.43. Reactivity to the cold pressor test yielded heritability estimates from 0.21 to 0.55. An ensuing review of genetic association studies revealed a number of genes, mostly within the sympathoadrenal pathway, that may account for part of the heritability of cardiovascular stress reactivity. Future progress in gene finding, that should include measures of sympathetic and vagal stress reactivity, may help uncover the molecular pathways from genetic variation to stress reactivity.

Physiological responses to workload change. A test/retest examination

The purpose of this study is to examine the test/retest consistency of physiological responses induced by mental tasks. Fifteen healthy male university students were recruited as participants. They were instructed to perform a 5-min Multi-Attribute Task Battery (MATB) trial three times successively. The task difficulty level of the tracking task of the second trial was set as medium (M). The first one was set as more difficult (H) and the last trial was easiest (L). The difficulty levels of the other two tasks (resource management and system monitoring) of the MATB were identical for all three trials. The participants repeated this procedure on three different days separated by at least a 1-day interval. The order of the tasks was the same for all repeated trials, i.e., H-M-L. Tissue blood volume from the tip of the nose using a laser Doppler blood flow meter, skin potential level (SPL), ECG from three leads on the chest, systolic time intervals (pre-ejection period, left ventricular ejection time), and hemodynamic parameters (stroke volume, cardiac output) were recorded during the task trials and before and after 5-min resting periods. The participants reported their subjective workload via NASA-TLX after each task trial. Autonomic nervous system parameters derived from the above-mentioned signals, subjective workload scores, and performance indices of MATB were analyzed, and test/retest reliability was investigated. The results showed that a significant test/retest correlation was obtained for SPL for more participants than in the other parameters, although there were large individual differences.

Longitudinal platelet reactivity to acute psychological stress among older men and women

Platelet reactivity to acute stress is associated with increased cardiovascular disease risk; however, little research exists to provide systematic methodological foundations needed to generate strong longitudinal research designs. Study objectives were: 1) to evaluate whether markers of platelet function increase in response to an acute psychological stress test among older adults, 2) to establish whether reactivity remains robust upon repeated administration (i.e. three occasions approximately 1 year apart), and 3) to evaluate whether two different acute speech stress tasks elicit similar platelet responses. The 149 subjects (mean age 71 years) gave a brief impromptu speech on one of two randomly assigned topics involving interpersonal conflict. Blood samples drawn at baseline and post-speech were assayed using flow cytometry for platelet responses on three outcomes (% aggregates, % P-selectin expression, and % fibrinogen receptor expression). Three-level hierarchical linear modeling analyses revealed significant stress-induced increases in platelet activation on all outcomes (p < 0.001). No significant habituation on any measure was found. Additional reactivity differences were associated with male gender, history of myocardial infarction, and use of aspirin, statins, and antidepressants. The results demonstrate that laboratory acute stress tests continued to produce robust platelet reactivity on three activation markers among older adults over 3 years.

Trajectories of maternal depressive symptoms over her child's life span: relation to adrenocortical, cardiovascular, and emotional functioning in children

Maternal depression has a number of adverse effects on children. In the present study, maternal depressive symptoms were assessed (using the Center for Epidemiological Studies Depression Scale) when their child was 3 months, 6 months, 1 year, 2 years, 4.25 years, 6 years, 7 years, 8 years, and 10 years of age. At 9.5 years of age, children's (94 females, 82 males) depressive symptoms as well as cardiovascular and cortisol levels during baseline and two psychologically stressful tasks were measured. Using multilevel modeling, maternal depressive symptom trajectories were considered in relation to their child's adrenocortical and cardiovascular responses to acute stress. Our goal was to determine maternal depressive symptom trajectories for children with elevated cardiovascular and cortisol reactivity to acute stress and elevated depressive symptoms. In general, those mothers with chronically elevated depressive symptoms over their child's life span had children with lower initial cortisol, higher cardiac output and stroke volume in response to acute stress, lower vascular resistance during acute stress tasks, and significantly more depressive symptoms at 9.5 years of age. These results are discussed in the context of established associations among hypothalamic-pituitary-adrenal axis dysregulation, depression, and cardiovascular disease.

Acute psychosocial challenge and cardiac autonomic response in women: the role of estrogens, corticosteroids, and behavioral coping styles

Theoretical statements, as well as clinical and experimental data, suggest that the amplitude of cardiovascular reactivity to acute stressors can be a good predictor of preclinical and clinical cardiovascular states. The aim of the present study is to investigate the role of estrogens, the hypothalamic-pituitary-adrenocortical activity, and the behavioral profile in individual cardiac autonomic reactivity to brief laboratory stressors in women. Thirty-six adult, healthy women were exposed to a stress interview and a mental task test, each lasting 5 min. They were assigned to two experimental groups: D4, i.e. 4 days after menses beginning (follicular phase, n=18), and D14, i.e. 14 days after menses beginning (ovulatory phase, n=18). The cardiac measurements in the baseline, stress and recovery periods consisted in heart rate (average R-R interval) and parasympathetic tone (r-MSSD) quantification, while the HPA axis activity and stress reactivity were assessed via plasma cortisol and dehydroepiandrosterone concentrations. The ethological profile during the interview was drawn by means of non-verbal behavior analysis. The cardiac, adrenocortical and behavioral responses to the two stressors were similar in groups D4 and D14, despite significantly higher estradiol levels in the latter. Subjects with higher pre-stress cortisol levels had higher heart rate and lower vagal activity in the baseline, stress and recovery phases. Women showing higher level of submission were characterized by higher heart rate acceleration and vagal withdrawal during both the interview and the recovery phase. In addition, the subjects that exhibited greater displacement during the interview were also characterized by lower heart rate increments and less pronounced vagal suppression during post-stress recovery. In conclusion, the present results do not support a clear buffering role of estrogens in cardiovascular response to acute stressors. However, they confirm that baseline HPA axis activity can be predictive of cardiac autonomic activity and stress responsiveness. They also highlight the modulating role of the individual style of behavioral coping in cardiac sympathovagal stress reactivity. Therefore, the objective assessment of the individual behavioral profile via the analysis of non-verbal communication patterns might represent a powerful tool for identifying subjects with higher risk of cardiac events.

Ambulatory impedance cardiography: a systematic review

BACKGROUND

Standard noninvasive impedance cardiography has been used to examine the cardiovascular responses of individuals to a wide range of stimuli in critical care and laboratory settings. It has been shown to be a reliable alternative to invasive thermodilution techniques and an acceptable alternative to the use of a pulmonary artery catheter. Ambulatory impedance cardiography provides a similar assessment of cardiac function to standard noninvasive impedance cardiography, but it does so while individuals engage in activities of daily living. It offers portability and the option of managing complex patients in outpatient settings.

OBJECTIVE

To critically examine through a literature analysis the validity, reliability, and sensitivity of ambulatory impedance cardiography for the assessment of cardiac performance during activities of daily living.

METHODS

The Cochrane Database of Systematic Reviews (CDSR), The Cochrane Database of Methodology Reviews (CDMR), The Cochrane Central Register of Controlled Trials (CENTRAL), Database of Abstracts of Reviews of Effects (DARE), National Health Service Economic Evaluation Database (NHS EED), Health Technology Assessment (HTA), and The Cochrane Methodology Register (CMR; 1966-2005); MEDLINE (1950-2005); and CINAHL (1982-2005) were searched using the following terms: ambulatory cardiac performance, impedance cardiac performance, AIM cardiac performance monitor, thoracic electrical bio-impedance, impedance cardiography, ambulatory impedance monitor, bio-impedance technology, ambulatory impedance cardiography, bio-electric impedance; also included were reference lists of retrieved articles. Studies were selected if they used an ambulatory impedance monitor to examine one or more of the following cardiovascular responses: pre-ejection period (PEP), left ventricular ejection time (LVET), stroke volume (SV), or a combination of these.

RESULTS

Studies have been predominantly descriptive and have been focused on a young, male population with a normal body mass index (BMI; 25-29 kg/m). Inconsistencies in determining specific markers of cardiac function (e.g., PEP and SV) across studies necessitated that results be reported by outcome for each study separately.

DISCUSSION

Ambulatory impedance monitors are valid and reliable instruments used for the physiologic measurement of cardiac performance. Sensitivity is established utilizing within-individual measurements of relative change. This is especially important in light of an aging population and technical advances in healthcare. Further research is warranted using nursing interventions that focus on an older, female population who have a BMI greater than 30 kg/m. Availability of noninvasive ambulatory measures of cardiac function has the potential to improve care for a variety of patient populations, including those with hypertension, heart failure, pain, anxiety, and depressive symptoms.

Terrorism and cardiovascular responses to acute stress in children

A number of studies have considered whether background stress affects cardiovascular responses to acute stress tasks. The present study considers the effect of a potent background stressor with a clear onset, namely the terrorist attacks on September 11, 2001. Specifically, the authors investigated differences among 9.5-year-old children tested before (N = 30) and then following (N = 20) the 9/11 attacks. In addition, a majority of these children (N = 37) were retested approximately 1 year later (i.e., before and after 9/11/2002). Children tested directly following 9/11/2001 exhibited significantly greater stroke volume and cardiac output responses to acute stress tasks compared with their responses 1 year later, and this change in reactivity differed significantly from the change in reactivity exhibited by children tested before 9/11/2001 and again 1 year later. These results suggest that a potent background stressor can temporarily heighten some children's cardiovascular responses to subsequent acute stressors.

Relation of cognitive appraisal to cardiovascular reactivity, affect, and task engagement

The relation of primary cognitive appraisals to cardiovascular reactivity, affect, task engagement, and perceived stress was examined in 56 men (ages 18-29). Systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate, preejection period, stroke index, cardiac index, and total peripheral resistance were assessed at rest and during performance of a computerized mental arithmetic task. Extending on prior investigations, threat and challenge appraisals were assessed independently from one another and from secondary appraisals. Positive and negative affect, task engagement, and levels of perceived stress were also assessed. Results indicated that threat (R2 =.08, p =.01), challenge (R2 =.14, p =.003), and their interaction (R2 =.11, p =.006) independently predicted DBP reactivity; DBP responses were greatest among participants with a high threat/low challenge pattern of appraisal. Threat appraisals predicted greater negative affect (R2 =.32) and perceived stress (R2 =.48), whereas challenge appraisals were related to greater positive affect (R2 =.44) and task engagement (R2 =.40, ps <.0001). Greater positive affect was correlated with increased SBP and DBP reactivity, and greater levels of task engagement with increased DBP response (ps < or = .002). Results suggest that primary cognitive appraisals are more potent predictors of affect and task engagement than cardiovascular reactivity.

Cardiovascular reactivity and development of preclinical and clinical disease states

OBJECTIVE

The objective of this review is to evaluate the evidence for the hypothesis that cardiovascular reactivity can predict the development of preclinical (elevated blood pressure, ventricular remodeling, carotid atherosclerosis) and/or clinical cardiovascular disease states.

METHODS

A review of the literature was conducted examining prospective studies.

RESULTS

Three large epidemiological studies with long-term follow-up periods (20 years or more) have found blood pressure responses to the cold pressor task to be predictive of subsequent essential hypertension in initially normotensive samples. Studies showing less consistent results have tended to use shorter-term follow-up periods. A larger body of literature demonstrates consistent associations between stress-related cardiovascular reactivity and blood pressure elevations in youth over the course of 1 to 6 years; such relationships have not been consistently shown among adult samples. Moderately consistent evidence points to a positive relationship between reactivity and other measures of subclinical disease (increased left ventricular mass and carotid atherosclerosis) among the few prospective studies that have examined these issues to date. A number of additional factors, however, such as baseline levels of disease risk and exposure to psychosocial stress, seem to moderate these relationships. Health status at baseline also seems to moderate the association between reactivity and clinical coronary heart disease in recent reports: two of three existing studies in initially healthy samples show no evidence of a relationship between reactivity and clinical outcomes, whereas three of four studies in samples with preexisting coronary heart disease or essential hypertension show a positive relationship between reactivity and subsequent disease states.

CONCLUSIONS

There is reasonable evidence to suggest that cardiovascular reactivity can predict the development of some preclinical states (eg, increased left ventricular mass and blood pressure) states and perhaps even new clinical events in some patients with essential hypertension or coronary heart disease. However, much more information is needed concerning moderating and potentially confounding variables before the robustness of the positive relationships can become clinically useful.

Dissecting the genetic architecture of the cardiovascular and renal stress response

We review the evidence for a genetic basis of the cardiovascular and renal stress response. A bio-behavioral model of stress-induced hypertension is presented that explains how repeated exposure to stress in combination with genetic susceptibility might lead to the development of hypertension. In this model, we focus on three underlying physiological systems that mediate the stress response of the heart, vasculature and kidney: the sympathetic nervous system (SNS), the renin-angiotensin-aldosterone system (RAAS) and the endothelial system (ES). We then review the evidence for a genetic influence on cardiovascular reactivity to psychological stress and stress-induced sodium retention using data from twin and family studies and a limited number of candidate gene studies. Finally, by describing the underlying physiological systems of our model and their genetic underpinning we emphasize the importance of inclusion of genetic measurements in any future studies testing the reactivity hypothesis.

Relationship of clinic, ambulatory, and laboratory stress blood pressure to left ventricular mass in overweight men and women with high blood pressure

OBJECTIVE

This study was designed to evaluate the relationship between left ventricular (LV) mass and blood pressure (BP) recorded in the following contexts: in the clinic, using standard auscultatory procedures, during a typical day using ambulatory BP monitoring, and in the laboratory environment during behavioral stress testing.

METHODS

Ninety-seven men and women with clinic systolic blood pressure (SBP) of 130 to 180 mm Hg and/or diastolic blood pressure (DBP) of 85 to 110 mm Hg and mild to moderate obesity were included in the study. Laboratory stressors included the following tasks: Public Speaking; Anger Interview; Mirror Trace; and Cold Pressor. LV mass was measured using echocardiography and adjusted for body size by dividing by height(2.7) to yield LV mass index (LVMI).

RESULTS

LVMI was positively correlated with clinic SBP (r = 0.24, p <.05), ambulatory SBP (r = 0.34, p <.01), and aggregated laboratory stress SBP (r = 0.28, p <.01). Of the individual stressors, only SBP responses to the Mirror Trace and Cold Pressor tasks were independently correlated with LVMI (r = 0.35 and 0.34, respectively, p values <.01). Hierarchical regression analyses revealed that laboratory stress SBP remained a significant predictor of LVMI, after controlling for BMI and clinic pressure.

CONCLUSIONS

These findings suggest that cardiovascular responses to behavioral stress are associated with individual differences in LVMI in men and women with high blood pressure who are overweight. Laboratory studies of behavioral stress may help promote our understanding of the pathophysiology of LVH.

Psychophysiological correlates of individual differences in patterns of hemodynamic reactivity

The present study delineates a method for the quantification of six hemodynamic reactivity patterns, in response to a laboratory stressor, and examines the psychophysiological correlates of individual differences in these patterns. One hundred and ninety-four young adult men and women participated in rest periods and two laboratory stressors, mental arithmetic and an anger recall interview. Measures were taken of blood pressure, heart rate, and cardiac output, from which total peripheral resistance was derived, as well as state reports of feelings during the tasks. Six hemodynamic reactor patterns were identified: Non-reactors, Mild Myocardials, Mild Vasculars, Myocardials, Vasculars, and Dual Reactors, each associated with a unique profile of cardiac output and total peripheral resistance change. Myocardial reactors to the interview had the highest resting levels of blood pressure and total peripheral resistance. Dual reactors had the largest increases in diastolic reactivity; Dual and Myocardial reactors had the largest increases in systolic reactivity. The extreme reactor groups (Dual, Myocardial, Vascular) all reported greater task invigoration than the Non-reactors, who reported greater efforts to relax. Reactor groups were similar on anger-related trait affect. Based on both resting blood pressure and magnitude of task-induced reactivity, Myocardial and Dual reactors may be at the greatest risk for subsequent hypertension.

Effects of exercise and weight loss on mental stress-induced cardiovascular responses in individuals with high blood pressure

The purpose of this study was to determine the effects of exercise and weight loss on cardiovascular responses during mental stress in mildly to moderately overweight patients with elevated blood pressure. Ninety-nine men and women with high normal or unmedicated stage 1 to stage 2 hypertension (systolic blood pressure 130 to 179 mm Hg, diastolic blood pressure 85 to 109 mm Hg) underwent a battery of mental stress tests, including simulated public speaking, anger recall interview, mirror trace, and cold pressor, before and after a 6-month treatment program. Subjects were randomly assigned to 1 of 3 treatments: (1) aerobic exercise, (2) weight management combining aerobic exercise with a behavioral weight loss program, or (3) waiting list control group. After 6 months, compared with control subjects, participants in both active treatment groups had lower levels of systolic blood pressure, diastolic blood pressure, total peripheral resistance, and heart rate at rest and during mental stress. Compared with subjects in the control group, subjects in the exercise and weight management groups also had greater resting stroke volume and cardiac output. Diastolic blood pressure was lower for the weight management group than for the exercise-only group during all mental stress tasks. These results demonstrate that exercise, particularly when combined with a weight loss program, can lower both resting and stress-induced blood pressure levels and produce a favorable hemodynamic pattern resembling that targeted for antihypertensive therapy.

Shared and Simple Effects of Determinants of Mean Arterial Pressure During Handgrip and Mirror Tracing Tasks

Abstract Hierarchical linear regression (HLR) can be used to quantify the relative contribution specific cardiovascular (CV) mechanisms make to blood-pressure responses. The impact particular mechanisms exert varies depending on the nature of situational demands and the length of time these demands have been imposed. Theoretically, the determinants of blood-pressure changes may exercise their influence independently as simple effects, or they might evidence a relationship that is correlated or shared with other mechanisms. Following a procedure Lindenberger and Potter (1998) outlined, we used HLR and computations of shared versus simple effect ratios to quantify the portions of variance several cardiovascular parameters accounted for independently in mean arterial pressure (MAP) reactivity during isometric handgrip and mirror tracing. The predictor variables included heart rate (HR), total peripheral resistance (TPR), and cardiac output (CO). CV activity of 50 college-aged males was measured during adjacent 30-s periods using impedance cardiography and a Dinamap blood pressure monitor. HR reactivity predicted MAP changes during all measurement periods. However, for mirror tracing, a substantial portion of the variance in MAP accounted for by HR was shared with CO reactivity (39% for period 1; 13% for period 2). For handgrip, 5% and 20% of variance HR accounted for in MAP during periods 1 and 2, respectively, were shared with changes in TPR. CO shared trivial amounts of variance in MAP changes with HR during handgrip. Finally, CO changes were correlated with TPR changes and uncorrelated with MAP reactivity when handgrip was performed. However, adding CO to the equation improved TPR's predictive utility, suggesting that suppressor effects were present.

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.

Relationship between left ventricular mass and hemodynamic responses to physical and mental stress

OBJECTIVE

Increased left ventricular mass (LVM) is predictive of future cardiac morbidity and mortality. Although casual and ambulatory blood pressure (BP) predict LVM, other hemodynamic determinants of LVM are incompletely understood. The present study examines laboratory-induced hemodynamic responses (to exercise, cold, and mental stress) and 24-hour ambulatory measures as predictors of LVM.

METHODS

Thirty-six healthy non-hypertensive subjects (mean age 33.9 +/- 9.4 years; 23 women, 13 men) were tested with mental stress, cold pressor, and treadmill exercise in the laboratory and 24-hour ambulatory BP monitoring. LVM was measured using two-dimensional targeted M-mode echocardiography and indexed for body surface area (LVMI).

RESULTS

All laboratory tasks produced significant hemodynamic responses (p's < 0.01). Systolic blood pressure responses to mental stress (r = 0.42, p < 0.01) and cold pressor (r = 0.34, p < 0.05) were significantly related to LVM. After adjusting for body size, the mental stress-induced SBP responses was the only significant predictor of LVMI (r = 0.32, p < 0.05). Exercise SBP responses were associated to LVMI in men (r = 0.63, p = 0.02), but not in women (r = 0.02, p = n.s.). Multivariate regression analyses revealed that SBP during mental stress was significantly predictive of LVMI (beta = 0.65, p = 0.05), independent of baseline SBP, 24-hour ambulatory SBP, and other control variables.

CONCLUSION

The present results indicate that SBP responses to mental stress are significantly related to LVM among healthy individuals, independently of baseline SBP, 24-hour ambulatory BP, age, body size, and sex. Blood pressure responses to exercise show a robust association with LVM in men but not in women. Hemodynamic responses elicited during laboratory tasks may therefore reveal important information about the pathophysiological processes involved in the development of cardiac end-organ damage.

Role-played interpersonal interaction: ecological validity and cardiovascular reactivity

Conflictual role-play scenarios have been used to model brief interpersonal interaction and to elicit cardiovascular reactivity in the laboratory. Here we discuss data suggesting that role-played interactions constitute an ecologically valid laboratory task that may improve laboratory-to-field generalization of cardiovascular response. Specifically, our research indicates that young adults perceive the stress associated with role-play scenarios as similar to that encountered in everyday life. Furthermore, these stress appraisals moderate cardiovascular response to role-play in men. We also find that a social stressor (i.e. speech task) is perceived as significantly more similar to a real-life stressor as compared to other standard laboratory tasks. We propose that particular constellations of cognitive, affective, and behavioral responses to laboratory-based social stressors, such as role-played interaction, may elicit different patterns of hemodynamic response. Further understanding of interrelations among cognitive, affective, behavioral, and physiological response patterns may assist in the study of cardiovascular reactivity as a potential mechanism linking personality factors and the development of cardiovascular disease.

The effects of epinephrine administration on impedance cardiographic measures of cardiovascular function

The effects of epinephrine administration on cardiovascular function were examined in 26 men who were given a bolus injection of either 1:10,000 epinephrine hydrochloride or physiological saline. Impedance cardiographic and continuous blood pressure measures were recorded during a 2-min pre-injection baseline and in the post-injection period. Compared to a saline control, epinephrine elicited greater shortening of heart period, pre-ejection period, and the R-B interval; greater increases in cardiac output, stroke volume, dZ/dt amplitude, Heather Index, and systolic and diastolic pressures; and greater decreases in total peripheral resistance (all P < 0.05). Left ventricular ejection time and the Q-R interval were not affected. The results indicate that inotropic indices that are readily measured by impedance cardiography should be considered as important non-invasive indices of adrenergically mediated responses to stress.

Ambulatory impedance cardiography: a feasibility study

A wearable, ambulatory impedance monitor (AIM) has been developed to permit impedance cardiographic measurements while patients and volunteers engage in normal daily activities. The AIM system was developed for use with a new hybrid tetrapolar spot-band electrode configuration and was designed to be comfortable and inconspicuous. The objective of the present study was to provide a preliminary evaluation of AIM comparability with the widely validated Minnesota model 304B impedance cardiograph with standard tetrapolar band electrodes. Orthostatic challenge was used to systematically alter cardiac function in a laboratory setting in 11 healthy men and women. Both while the subjects were sitting and while they were standing, the AIM yielded measures of cardiac function, including heart rate, preejection period, left ventricular ejection time, and stroke volume, that were similar to those acquired by using the reference Minnesota 304B system (all Pearson R correlations > +0.87, all P < 0. 001). Cardiac responses to postural shift, expressed as change measures from sitting to standing, were also comparable for the AIM and Minnesota reference monitoring systems. Potential applications, including the assessment of 24-h hemodynamic profiles, are illustrated and discussed.

Power spectral analysis of heart rate variability in type A females during a psychomotor task

This study investigated changes in autonomic nervous activities due to psychological stress in Type A females. Eight Type A and eight Type B females performed a psychomotor task for 30 minutes. Power spectral analysis of heart rate variability (HRV) was used to examine the autonomic nervous activities. Results showed the low frequency (LF) component and LF/HF ratio in Type A females increased after the onset of the task. There were no significant differences in task performance between Type A and Type B females. The subjective mental workload increased gradually in Type A females during the tasks, whereas in Type B females this parameter did not change in a consistent manner. The results suggest that the sympathetic nervous system in Type A females was more stimulated by the task and Type A females felt a greater subjective mental workload than did Type B females.

Postural effects on hemodynamic response to interpersonal interaction

Laboratory studies of stress-induced cardiovascular reactivity have been conducted predominantly with participants in a seated posture. This procedure may contribute to limited laboratory-field generalization of cardiovascular response. The present study examined hemodynamic adjustments underlying pressor responses, in addition to heart rate and systolic time intervals, during seated and standing role-played, interpersonal interaction in 60 young adults. Irrespective of gender or race, blood pressure responses to the seated and standing interactions were comparable. However, seated interactions yielded a significantly greater increase in heart rate, shortened preejection period and decreased stroke index as compared to standing. Alternatively, interacting while standing yielded a significantly increased left ventricular ejection time and total peripheral resistance in comparison to sitting. These results suggest that hemodynamic adjustments during stressful interpersonal interaction vary as a function of posture, with somewhat greater cardiac influences apparent while seated and a more pronounced vascular response while standing.

Active coping and cardiovascular reactivity: a multiplicity of influences

OBJECTIVE

Active coping enhances cardiovascular response presumably by beta-adrenergically mediated myocardial activation. This study examined impedance-derived hemodynamic parameters underlying blood pressure response to two laboratory tasks requiring active coping, performed either with or without an appetitive (i.e., monetary) incentive.

METHOD

Forty-eight healthy, young men completed the Stroop Color-Word Test and Mirror Tracing. Half received no incentive, whereas half were provided with a monetary incentive as an active coping manipulation. Task-related changes in blood pressure, heart rate, systolic time intervals, and hemodynamic parameters were monitored. Psychological responses to the tasks were also obtained.

RESULTS

On average, incentive virtually doubled blood pressure response to both Stroop and Mirror Tracing. The change in blood pressure was explained predominantly by a concomitant increase in total peripheral resistance. Heart rate response was also enhanced substantially with incentive. Individuals in the incentive condition reported greater interest in the task, but less perceived control, than persons in the no-incentive condition.

CONCLUSIONS

The incentive-related increase in total peripheral resistance, combined with an absence of enhanced stroke volume, cardiac output, or preejection period response, indicates that active coping may, under certain conditions, elevate blood pressure via increased systemic resistance, presumably reflecting alpha-adrenergic activation. Furthermore, the enhanced heart rate associated with incentive may reflect a withdrawal of parasympathetic influence.