Hemodynamics during rest and behavioral stress in normotensive men at high risk for hypertension

Persons at risk for hypertension may show elevated blood pressure (BP) at rest and during mental stress; however, the hemodynamics underlying the BP of those persons at high risk are not well characterized. We chose 21 high risk and 21 low risk men using their parental hypertension history and resting systolic blood pressures on two screenings. Then, on a day of extended rest versus a day with prolonged mental arithmetic and reaction time tasks, we examined whether high risk BP elevations reflected greater vascular resistance or cardiac output. High risk men had raised systolic/diastolic pressures ( F s = 74/15, p s < .0001/.0001) and higher vascular resistance ( F = 6.6, p < .02) with minimal differences in heart rate and cardiac output. This finding implicates vascular resistance as the altered element in BP control in these high risk men tested in a familiar environment with minimal task-related threat.     

Heart Rate Reactivity and Type A Behavior as Modifiers of Physiological Response to Active and Passive Coping

We examined the long term predictivity of heart rate reactivity (HRR) and its relation to cardiovascular and biochemical activity during rest and during tasks requiring active and passive coping. HRR was determined in 28 young men by measuring peak heart rate change to cold pressor one year after performing tasks eliciting active and passive coping. Heart rate change to cold pressor was significantly correlated with change to active coping (r= .65, p<.01) and to passive coping (r= .53, p<.01). Responses to the tasks were equivalent for Type A and B subjects. On the other hand, high HRRs were significantly more reactive than low HRRs with the effect being most apparent during active coping. HRR appeared to be a trait stable over one year which predicted enhanced cardiac, neuroendocrine, and neuromuscular response.     

Effects of Coping on Blood Pressure Responses to Threat of Aversive Stimulation

The purpose of this study was to examine effects on systolic and diastolic blood pressure due to availability and difficulty of control over anticipated aversive auditory stimulation. In a 2 × 2 factorial design, 44 subjects were presented either of two instructional sets regarding control: a) that exposure to the aversive stimulus would be contingent on the subject's performance at a cognitive task (Control), or b) that the stimulus would occur at random during the task period (No Control). The experimental task consisted of problems in concept formation and was presented to Control and No Control subjects at either of two levels of difficulty (Difficult or Easy); task success was manipulated by the experimenter to assure equivalent performance across groups. Results indicated that within the Task Difficult condition, Control subjects evidenced greater systolic blood pressure elevations than subjects in the No Control group, whereas Control and No Control subjects in the Task Easy condition showed no reliable differences. Diastolic blood pressure did not vary by control or task difficulty. It was concluded that the availability of control responses may induce greater arousal in situations involving threat of aversive stimulation, but that this effect obtains only when subjects experience some degree of difficulty employing available coping strategies.     

Activation Patterns to Aversive Stimulation in Man: Passive Exposure Versus Effort to Control

The present study contrasted physiological response patterns occurring when subjects coped passively and actively with aversive stimuli. In one condition, 29 healthy young men were exposed to unpredictable noise (115BA) and shock (3.5 mA) with no means of control, and in the other they attempted to avoid the noise and shock with rapid keypresses. Both tasks were characterized by maximal uncertainty as to locus of presentation, chance of occurrence, and type of stimulus to occur next in sequence. Dependent variables included: reports of moods, reaction times, muscle tension, plasma concentrations of free fatty acids, cortisol and catecholamines, heart rate, blood pressures, systolic time intervals, cardiac output, systemic vascular resistance, and an index of myocardial contractility. Both experimental conditions produced significant neuroendocrine, lipid, and cardiovascular changes from baseline. The active avoidance procedure produced further increases in cardiac function which were related to control efforts as indexed by muscle tension and task performance. The results point toward the effects of effort in the face of uncertainty in determining the patterns of response to aversive stimulation.     

Comparison of hemodynamic responses to social and nonsocial stress: evaluation of an anger interview

Hemodynamic responses to an anger interview and cognitive and physical stressors were compared, and the stability of associated hemodynamic reactions examined. Participants experienced control, handgrip, counting, and mental arithmetic tests and an anger interview on two occasions. Systolic and diastolic blood pressure, heart rate, stroke volume, and cardiac output were measured. Total peripheral resistance was also derived. The anger interview produced larger, more sustained changes in blood pressure in both sessions than the other stressors. These changes were largely a consequence of increased peripheral resistance. Consistent with previous findings, handgrip was associated with a resistance-type reaction whereas arithmetic was associated with a cardiac output-type reaction. There was low-to-modest stability of hemodynamic reactions to the interview. Further research is necessary to optimize its utility in studies of cardiovascular function. Nevertheless, the findings underscore the ability of ecologically relevant stressors to provoke unique configurations of cardiovascular activity.     

体外反搏对犬血流脉动性和血管阻力的影响

为了评价体外反搏是否具有扩张血管和增加血流脉动性的作用 ,制造了犬急性心肌梗塞模型 ,并使犬存活 6周。麻醉后 ,测定左侧颈总动脉血流量和右侧颈总动脉血压。计算反搏前和反搏中脉压差、血压脉动指数、血压的标准差、流量差、流量脉动指数、流量标准差和平均血管阻力。结果显示脉压差、血压脉动指数和血压标准差三个血压脉动性指标分别由反搏前的 30± 9mm Hg、1.2 6± 0 .0 5、8.7± 2 .5 mm Hg升高到反搏中的 4 3± 8mm Hg(P<0 .0 5 )、1.5 4± 0 .13、12 .4± 2 .0 mm Hg (P<0 .0 5 )。流量差、流量脉动指数和流量标准差三个血流脉动性指标分别由反搏前的 317± 4 8ml/ min、2 .85± 0 .2 1、96± 2 1ml/ min升高到反搏中的 4 4 7± 88m l/ min、4 .5 6± 0 .90、131±39m l/ m in,P值均于小 0 .0 5。平均血管阻力由反搏前的 5 78± 72 Wood单位降低到反搏中的 4 76± 85 Wood单位(P<0 .0 5 )。这表明体外反搏可使血管阻力下降 ,血压和血流脉动性增强。     

Difference in human cardiovascular response between upright and supine recovery from upright cycle exercise

Cardiovascular responses were examined in seven healthy male subjects during 10 min of recovery in the upright or supine position following 5 min of upright cycle exercise at 80% peak oxygen uptake. An initial rapid decrease in heart rate (f _c) during the early phase of recovery followed by much slower decrease was observed for both the upright and supine positions. The average f _c at the 10th min of recovery was significantly lower (P < 0.05) in the supine position than in the upright position, while they were both significantly greater than the corresponding pre-exercise levels (each P < 0.05). Accordingly, the amplitude of the high frequency (HF) component of R-R interval variability (by spectrum analysis) in both positions was reduced with a decrease in mean R-R interval, the relationship being expressed by a regression line – mean R-R interval = 0.006 × HF amplitude + 0.570 (r = 0.905, n = 28, P < 0.001). These results would suggest that the slower reduction in f _c following the initial rapid reduction in both positions is partly attributable to a retardation in the restoration of the activity of the cardiac parasympathetic nervous system. Post-exercise upright stroke volume (SV, by impedance cardiography) decreased gradually to just below the pre-exercise level, whereas post-exercise supine SV increased markedly to a level similar to that at rest before exercise. The resultant cardiac output (Q˙ _c) and the total peripheral vascular resistance (TPR) in the upright and supine positions returned gradually to their respective pre-exercise levels in the corresponding positions. At the 10th min of recovery, both average SV and Q˙ _c were significantly greater (each P < 0.005) in the supine than in the upright position, while average TPR was significantly lower (P < 0.05) in the supine than in the upright position. In contrast, immediately after exercise, mean blood pressure dropped markedly in both the supine and upright positions, and their levels at the 10th min of recovery were similar. Therefore we concluded that arterial blood pressure is maintained relatively constant through various compensatory mechanisms associated with f _c, SV, Q˙ _c, and TPR during rest and recovery in different body positions. Accepted: 4 September 1999     

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.     

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.     

Respiratory Sinus Arrhythmia as an Index of Parasympathetic Cardiac Control During Active Coping

Psychophysiological studies concerning tonic cardiac responses to stressor tasks have tended to emphasize beta-adrenergic effects and to neglect parasympathetic influences and sympathetic-parasympathetic interactions. Much recent evidence indicates that both within- and between-individual variations in cardiac parasympathetic heart rate (HR) control can be easily and reliably assessed by measuring the magnitude of respiratory sinus arrhythmia (RSA). Therefore, we used RSA to index cardiac vagal responses to two active coping tasks. Both tasks consisted of the same video game, in one condition with threat of shock for inferior performance, and in the other without such threat. Twenty subjects underwent both tasks (counterbalanced over subjects), plus a preceding resting baseline period. HR and RSA were continuously measured. Results suggested that cardiac parasympathetic activity was diminished from rest to task, contributing to heart rate responses. Exaggerated HR responses were also associated with extreme parasympathetic withdrawal. Furthermore, task condition X sequence of presentation interaction effects showed that threat of shock was particularly effective in elevating HR and reducing RSA when the threat was presented during the first task condition. A repeated-measures analysis of covariance of HR, attempting to remove the effects of parasympathetic influences upon HR, suggested that sympathetic influences upon HR exceeded any reciprocal vagal effects during the threat condition for those subjects exposed to the threat task first. The findings indicate the importance of considering stress-related parasympathetic effects upon HR as well as sympathetic-vagal interactions.     

大学生应对方式与犬儒态度的关系研究

目的 探讨大学生应对方式与犬儒态度之间的关系.方法 采用简易应对方式问卷和犬儒态度量表对西北工业大学320名学生进行问卷调查,并用SPSS17.0进行数据整理和相关分析.结果 ①积极应对与犬儒态度(r=-0.688,P＜0.001)呈显著负相关;②消极应对与犬儒态度(r=0.600,P＜0.001)及其他4个维度呈显著正相关;③回归分析显示积极应对对犬儒态度有负向预测作用(t=-17.078,P＞0.001),消极应对对犬儒态度有正向预测作用(t=13.509,P＞0.001).结论 大学生应对方式是影响犬儒态度的重要心理因素.     

Pregnancy Alters Blood Pressure Responses to Psychological and Physical Challenge

The purpose of the study was to evaluate the effect of the substantial changes in female reproductive hormones that occur during normal pregnancy on cardiovascular responses to psychological and physical challenges. Twenty-one healthy normotensive women performed serial subtraction, mirror image tracing, and isometric handgrip exercise tasks prior to pregnancy and again during the second trimester of pregnancy. A control group of 34 healthy women who did not intend to become pregnant and were nonpregnant were also tested in the same protocol twice, 6-10 months apart. Results showed that the pregnant women exhibited a reduced diastolic blood pressure response to all three tasks, relative to their pre-pregnancy levels, whereas nonpregnant controls did not change in their diastolic blood pressure response across time. These results are consistent with the hypothesis that elevations in female reproductive hormones diminish blood pressure responses during challenge because of dampened sympathetic nervous system activity.     

Postural stability of hemodynamic responses during mental challenge

Laboratory stress testing is typically conducted while subjects are seated, whereas real-life stressors may often be encountered while standing. The present study of 20 healthy young men evaluated blood pressure and underlying hemodynamic adjustments to a standardized mental arithmetic task performed twice while seated and twice while standing. Blood pressure increased during mental arithmetic in both postures, but the underlying hemodynamic determinants of the pressor responses were different for the two postures. Augmented cardiac output was responsible for increasing blood pressure during seated task performance, whereas increased vascular resistance was the mechanism for the pressor response to the task performed while standing. Blood pressure and hemodynamic responses were reproducible subject characteristics for a given posture; test-retest correlations were significant for all cardiovascular measures. However, seated blood pressure responses were not significantly correlated with standing blood pressure responses. In contrast, significant between-posture correlations were found for cardiac output and vascular resistance responses. This preliminary evidence of postural stability of the hemodynamic determinants of blood pressure responses during stress is consistent with growing evidence that hemodynamic response tendencies are robust characteristics of reactivity. Ambulatory monitoring of hemodynamic response patterns during real-life stress may reveal more idiosyncratic profiles of stress reactivity than are displayed by blood pressure responses alone.     

Hemodynamics during active and passive recovery from a single bout of supramaximal exercise

The aim of this work was to study the differences in cardiovascular response during two modes of recovery [active (AR): pedalling at 40 W; and passive (PR): complete rest seated] from a single bout of supramaximal exercise. Eight male amateur soccer players underwent two supramaximal cycle-ergometer tests, each consisting of pedalling against a resistance equivalent to 150% of the maximum workload achieved in a previous incremental test, followed by randomly assigned AR or PR. Cardiodynamic variables were obtained using an impedance cardiograph. Subjects were also connected to a sphygmomanometer, for systolic and diastolic blood pressure, and to a metabolimeter for oxygen uptake (V˙O₂) assessments. We measured: heart rate (HR), stroke volume (SV), cardiac output (CO), the inverse of myocardial contractility calculated as pre-ejection period/left ventricular ejection time ratio (PEP/LVET), mean blood pressure (MBP), thoracic electrical impedance (Z ₀) as an index of central blood volume, and arterio−venous oxygen difference (A−V O₂ Diff.). PR caused a lower CO compared to AR [mean (SE): 7 (0.7) vs. 10.4 (0.6) l·min⁻¹ at the 5th min of recovery] due to lower HR [106.2 (3.6) vs. 121.8 (4.5) bpm at the 5th min of recovery], SV [67.1 (5) vs. 86.1 (4.8) ml at the 5th min of recovery], and PEP/VET values [0.44 (0.007) vs. 0.39 (0.015) at the 5th min of recovery]. No differences were found in MBP and Z ₀ between PR and AR [95.1 (1.9) vs. 92.3 (2.7) mmHg and 26.2 (1.1) vs. 26.6 (1) Ω respectively at the 5th min of recovery], while A−V O₂ Diff. values were higher during AR than during PR [108.8 (4.3) vs. 75.2 (5.4) ml·l⁻¹ at the 5th min of recovery]. Thus, although after a single bout of supramaximal exercise SV and CO are lower during PR than during AR, these differences are not due to an impairment of cardiovascular function, but are fully explained by the lesser muscular engagement that leads to a reduction in stimuli deriving from mechanoreceptors and central commands, thus causing a faster return of myocardial contractility and HR to resting values. Electronic Publication     

Cardiovascular Responses to Effortful Active Coping: Implications for the Role of Stress in Hypertension Development

Recent contributions to the literature on stress and hypertension are discussed. The significance of effortful active coping in evoking sympathetically-mediated heart rate and blood pressure increases is supported by results of studies involving both aversive and appetitive task incentives. Young healthy males who are above-average in heart rate during coping tasks show consistently higher heart rates and systolic pressures during other stresses as well, but are indistinguishable from less reactive persons when relaxed. Studies involving beta-blockade indicate that these above-average cardiovascular increases are partly due to a greater beta-adrenergic response among the high heart rate reactors. In addition, the parents of these high heart rate reactors report a greater incidence of hypertension than parents of low reactors, suggesting that high cardiovascular responses during active coping stress may reflect a high degree of susceptibility to later hypertension.     

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.     

Evaluation of Beta-Adrenergic Influences on Cardiovascular and Metabolic Adjustments to Physical and Psychological Stress

This study was designed to examine the hypothesis that certain behavioral demands may tend to trigger sympathetic mechanisms which result in metabolically excessive cardiac output elevations. Oxygen consumption and cardiac output adjustments during a contrived reaction-time shock-avoidance task were compared to a cold pressor test in healthy young male adults. The linear cardiac output/oxygen consumption relationship generated by performance on a graded exercise task was used to assess the metabolic appropriateness of cardiac output adjustments to the reaction-time task and cold pressor. The reaction-time task was generally found to evoke metabolically excessive increases in cardiac output, while cardiac output adjustments to cold pressor were more consistent with changes in metabolic demands. However, the tasks were associated with similar heart rate responses, with a significant attenuation in stroke volume during cold pressor accounting for the differential alterations in cardiac output. This finding suggests a limited reliability for heart rate as an index of cardiac performance. The effects of propranolol, which was employed to evaluate the role of sympathetic influences, indicated that beta-adrenergic mechanisms were responsible for mediating the cardiac output response to the reaction-time task, but only partially contributed to the cold pressor response. Post-hoc analyses of individual differences in cardiovascular reactivity to the reaction-time task suggest that, for hyperreactive individuals, the coping responses evoked by this task may lead to tissue overperfusion with oxygen, thereby providing a stimulus for autoregulatory vascular reflexes which may be associated with the etiology of hypertensive disease.     

Psycho-Social Factors and Blood Pressure During Pregnancy and Delivery

This research investigates the relationship between repression and blood pressure by using an objective and well-known test for classifying subjects as repressors (Byrne's R-S scale), and examines the relationships among socio-economic level, ethnic origin, and blood pressure. Subjects were 461 Israeli pregnant women who gave birth in urban hospitals. The physiological measures were the highest blood pressure a woman had during pregnancy, as well as blood pressure, heart rate and temperature measured immediately after her admission to the hospital. The women's anxiety level was ranked before and after delivery. No confirmation was found for the psychoanalytically based hypothesis held by several investigators, that subjects with repressive personality type would have higher blood pressure. No significant relationship was found between socio-economic level and any physiological measure. Israeli Jews of Oriental origin had lower blood pressure than those of European origin, even though the former were of lower socio-economic level.     

Elimination of breathing artefacts from impedance cardiograms at rest and during exercise

A signal processing technique was developed by which breathing artefacts can be eliminated from impedance cardiograms. The breathing component of the transthoracic impedance signal is identified by a moving-window technique using linear regression analysis, the window span being determined by the current R-R interval of the ECG. Satisfactory beat-by-beat stroke volume measurements were obtained when the method was applied to eliminate simulated breathing artefacts superimposed on distortion-free impedance signals from human subjects. In subjects performing moderate to heavy exercise the potential capability of the method to retrieve the cardiogenic impedance signal in the presence of severe interference caused by exercise hyperpnoea was demonstrated, permitting distortion-free beat-by-beat stroke volume estimations.     

Effects of the muscle pump and body posture on cardiovascular responses during recovery from cycle exercise

The purpose of the study was to characterize the effects of muscular contractions (the muscle pump) and body posture on cardiovascular responses during recovery from moderate exercise in the upright-sitting or supine positions. Heart rate (HR), stroke volume (SV), and cardiac output (CO) were measured in seven young male subjects at rest and during 10-min of cycle exercise at 60% of peak oxygen uptake This was followed by either complete rest for 5 min (inactive recovery) or cycling at for 5 min (active recovery) in the upright or supine positions. In the upright position, an initial rapid decrease in HR was followed by a gradual decrease in HR, and this response was similar when comparing inactive and active recoveries. Upright SV during inactive recovery decreased gradually to the pre-exercise resting level, whereas upright SV during active recovery remained significantly elevated. In contrast, in the supine position, the HR during active recovery decreased, but remained significantly higher than that during inactive recovery. Changes in supine SV were similar when comparing inactive and active recovery. Thus, maintenance of SV and HR resulted in significantly greater CO during active recovery than during inactive recovery, regardless of body position. HR was greater during supine active-recovery than during supine inactive-recovery, and there was no difference in SV. These data suggest that the muscle pump is less important in facilitating venous return and vagal resumption in the supine position as compared to the upright position.