White coat effect and reactivity to stress: cardiovascular and autonomic nervous system responses

The aim of this study was to elucidate further the precise nature of the so-called "white coat" (WC) effect. We enrolled 88 hypertensive (46 men, 42 women) and 18 normotensive (4 men, 14 women) subjects in whom beat-to-beat blood pressure (BP) and heart rate (HR) were measured with a Finapres device at rest (R period) and during conventional BP measurement (WC period). The WC effect was defined as WC period minus R period values of Finapres systolic BP. Using the same method, we also measured the BP and HR variations induced by mental stress (MS period) and by assuming the standing position (S period). Variability was estimated in the frequency domain for BP (BPV) and HR (HRV) and gave indices of the autonomic nervous system. Pulse wave velocity was taken as an index of arterial distensibility. In hypertensive subjects, the WC effect was significantly and positively correlated with the BP response to stress (0.51, P<.0001) and standing (0.63, P<.0001). An increased BPV was observed in the low-frequency band (0 to 0.150 Hz) during WC, MS, and S periods. In normotensive subjects, the WC effect was very slight and not correlated with the responses to stress and standing. In this group, the WC period was not accompanied with an increased BPV, unlike the stress and standing periods. HRV was similar in normotensives and in hypertensives: decreased, unchanged, and increased during MS, S, and WC periods, respectively. The PWV was significantly increased in the hypertensives relative to the normotensives, even in the quartile of those with the lowest BP (on average similar to that of the normotensives). This work shows that the WC effect is associated with an enhanced BP response to standing and mental stress; these three situations are characterized by an increased BPV in the low frequencies, suggesting a similar modification of the sympathovagal balance. The WC effect may entail an increased risk because it is associated with impaired arterial distensibility.     

Hemorrhage exerts different effects on variabilities of heart rate and blood pressure in dogs

The aim of the present study was to evaluate the effects of hemorrhage on heart rate variability (HRV) and blood pressure variability (BPV) as indicators of autonomic nervous system (ANS) and hypovolemia. We induced hemorrhagic hypovolemia in 7 dogs by removing blood in graded stages (0%, 10%, 20%, 30%, 40% of the estimated blood volume; EBV). HR was unchanged during hemorrhage, while mean BP decreased significantly after 30% EBV hemorrhage. Low frequency component (LF: 0.04-0.15 Hz) of HRV significantly increased after 20% EBV hemorrhage but high frequency component (HF: 0.15-0.4 Hz) of HRV was not altered. LF of BPV increased significantly stepwise after 20% EBV hemorrhage and HF of BPV increased significantly after 30% EBV hemorrhage, showing that both LF and HF of BPV might indicate the degree of hypovolemia. During hemorrhage LF of HRV and BPV increased and HF of HRV was unchanged, indicating the shift of the autonomic balance toward sympathetic dominance. An excellent quantitative correlation between LF of BPV and the degree of hypovolemia was demonstrated during graded hemorrhage, while LF of HRV plateaued at its maximum value at 20% EBV hemorrhage. In conclusion, our study suggests that the spectral analysis of HRV and BPV during graded hemorrhage shows different characteristics in the quantitative evaluation of ANS and hypovolemia.     

Protein and calorie effects on progression of induced chronic renal failure in cats

This study was designed to determine if there is a difference in autonomic regulation induced by posture change between postmenopausal and young women. To evaluate autonomic nervous system function, spectral analysis of heart rate variability (HRV) was done in postmenopausal women (n = 13, 46-59 years of age), age-matched men (n = 8, 45-55 years of age), and young women (n = 10, 20-37 years of age) for 3-min periods of controlled frequency breathing (15 breaths/min) in supine followed by sitting positions. In the supine position, the R-R interval variation in older persons decreased significantly compared with that during the follicular phase in young women. Furthermore, the high-frequency (HF) components of HRV, which reflect only parasympathetic activity, were lower in older subjects than in young women. Following a change of position from supine to sitting, the HF component did not change significantly in the postmenopausal women or the men, but the low/high frequency (LF/HF) component ratio, which reflects the balance of autonomic nerve activities, increased significantly in the men. These results suggest that cardiac parasympathetic tone may be reduced in older persons in comparison with young women. Furthermore, arterial baroreflex control of parasympathetic nerve activity caused by posture changes is impaired in the postmenopausal women and aged-matched men. The baroreflex control of the sympathetic component is maintained in the men but not in the postmenopausal women. These differences might result in part from changes in the level of female hormones.     

Twenty-four hour time and frequency domain variability of systolic blood pressure and heart rate in an experimental model of arterial hypertension plus obesity]

Modifications of heart rate (HR) and systolic blood pressure (SBP) variabilities (V) have been reported in the human syndrome arterial hypertension plus insulin-resistance. The aim of this study was to characterize the 24 h SBPV and HRV in both time and frequency domains during weight increase in dogs fed ad libitum with a high fat diet. Implantable transmitter units for measurement of blood pressure and heart rate were surgically implanted in five beagle male dogs. BP and HR were continuously recorded using telemetric measurements during 24 hours, before and after 6 and 9 weeks of hypercaloric diet in quiet animals submitted to a 12h light-dark cycle. To study nychtemeral cycle of SBP and HR, two periods were chosen: day (from 6.00 h to 19.00 h) and night (from 23.00 h to 6.00 h). Spontaneous baroreflex efficiency was measured using the sequence method. Spectral variability of HR and SBP was analyzed using a fast Fourier transformation on 512 consecutive values and normalized units of low (LF: 50-150 mHz, reflecting sympathetic activity) and high (HF: respiratory rate +/- 50 mHz, reflecting parasympathetic activity) frequency bands were calculated. The energy of total spectrum (from 0.004 to 1 Hz) was also studied. Body weight (12.4 +/- 0.9 vs 14.9 +/- 0.9 kg, p < 0.05). SBP (132 +/- 1 vs 147 +/- 1 mmHg, p < 0.05) significantly increased after 9 weeks of hypercaloric diet. A nycthemeral HR rhythm was present at baseline (day: 79 +/- 1 vs night: 71 +/- 1 bpm) but not after 9 weeks (day: 91 +/- 4 bpm ; night: 86 +/- 2 bpm). Concomitantly, the efficiency of spontaneous baroreflex decreased at 6 weeks (36 +/- 1 vs 42 +/- 2 mmHg/ms, p < 0.05). A significant decrease in HF energy of HRV was found after 6 but not after 9 weeks. LF energy of SBPV was increased at 6 but not at 9 weeks (table). [table: see text] In conclusion, this study shows that an hyperlipidic and hypercaloric diet induces transient variations in autonomic nervous system activity which could be the physiopathological link between obesity, insulin-resistance and arterial hypertension.     

Reliability of noninvasive methods to measure cardiac autonomic function

Cardiac autonomic modulation was examined in 10 healthy subjects (mean age = 27.8 +/- 1.7) at rest (paced breathing at 12 and 16 breaths/min) and during a submaximal cycle ergometer exercise test. Heart rate variability (HRV) spectral parameters and spontaneous baroreflex (SBR) function variables showed no significant differences between mean values for any of the testing conditions. Spectral parameters and SBR function did not differ significantly between the resting conditions. Significant reliability coefficients (r = 0.59-0.73) were observed for all spectral parameters except low frequency power (r = 0.22) during 12 breaths/min, with moderately lower values during 16 breaths/min (r = 0.10-0.75) and exercise (r = 0.20-0.89). Significant reliability coefficients were observed for baroreflex sensitivity at 12 (r = 0.83) and 16 (r = 0.92) breaths/min. It was concluded that at rest, HRV spectral and SBR analyses are reliable methods for studying cardiac autonomic balance.     

Molecular study of the rhodopsin gene in retinitis pigmentosa patients in the Basque Country

INTRODUCTION: Clinically relevant autonomic disturbances have been reported for respirator-dependent ALS patients while subclinical involvement may be present in the early course. METHODS: Eighteen patients with early-stage ALS and 18 age-matched controls were studied by means of standard autonomic tests (heart off + response to deep breathing and tilt-table testing), and spectral analysis of heart rate (HR) and arterial blood pressure (ABP), using the associated transfer function as a measure of baroreflex sensitivity for the mid-frequency band (MF band, 0.05-0.15 Hz) and as a measure of cardiorespiratory transfer for the high-frequency band (HF band, 0.15-0.33 Hz). RESULTS: Mean HR and ABP were increased in ALS, while results of standard autonomic tests were similar for ALS and controls. Transfer function analysis revealed reduced baroreflex sensitivity and diminished cardiorespiratory transfer during normal breathing. CONCLUSIONS: Cardiovascular autonomic functions are intact in patients with ALS. There is evidence of sympathetic enhancement and vagal withdrawal, accompanied by reduced baroreflex sensitivity. These findings are similar to those reported for essential hypertension and may point to a common central autonomic derangement in both disorders.     

Psychosocial and ethical issues in surgical approaches to end-stage lung disease

This study aimed to determine whether alterations in cardiovascular dynamics before syncope are related to changes in spontaneous respiration. Fifty-two healthy subjects underwent continuous heart rate (HR), arterial blood pressure (BP), and respiratory measurements during 10-min periods of spontaneous and paced breathing (0.25 Hz) in the supine and 60 degrees head-up tilt positions. Data were evaluated by power spectrum and transfer function analyses. During tilt, 27 subjects developed syncope or presyncope and 25 remained asymptomatic. Subjects with tilt-induced syncope had significantly greater increases in low-frequency (0.04-0. 15 Hz) systolic BP, diastolic BP, and HR power during tilt than the asymptomatic subjects (P 相似文献   

Evaluation of the degree of diabetic dysautonomy with the analysis of heart rate measured at rest with the FINAPRES system

In this work, we developped the ERK (Eckmann, Ruelle and Khamporst) method of recurrent plots to analyse Heart Rate Variability (HRV), measured by the FINAPRES system in diabetic subjects. Our aim was to search some indices that might characterize the degree of dysautonomy detected in diabetic subjects, using the Ewing tests. The idea was to analyze the recurrences of the HR to previously observed values. When a value of HR, xi measured at the j-th beat come back to an already observed value, we compare the distances between the following measures (xi + 1 to xj + 1), (xj + 2 to xj + 2)... If the distances are under a given criteria during k beats, xi is deterministic of order k. Let n1 be the number of recurrent points and nk the number of k-order deterministic points, with k = 2, 3, 4... We defined the index of determinism nk + 1/nk and the Shannon entropy of the Nk = nk-nk + 1. These indices will be correlated to the total score of the 5 Ewing tests, which represent the standard measure to evaluate the diabetic dysautonomy. Blood pressure (BP) and HR were measured during about 30 minutes using the FINAPRES system in 44 healthy subjects and 60 non-hypertensive diabetic subjects. In the diabetic subjects, the age, the body weight and systolic and diastolic BP were 56 +/- 13 years (mean +/- standard-deviation), 79 +/- 14 kg, 80 +/- 10 mmHg and 137 +/- 20 mmHg. HR was weakly correlated to age (r = 0.29; p = 0.02) and the Ewing score (r = 0.31; p = 0.01). Its standard-deviation is also weakly correlated to age (r = 0.32; p = 0.01) and to the Ewing score (r = 0.34; p = 0.01). Using the ERK method, we obtained indices which are much more correlated to the Ewing score. In particular, the ratio n2/n1 and Shannon entropy were correlated to the Ewing score with r = 0.51 and r = 0.53, respectively (p < 0.0001 in both cases). These indices are also correlated to age (r = 0.40; p = 0.003) in both cases. The ERK method give some indices which are easy to obtain (measurement of HR during a rest period) and easy to interpret. These indices are strongly linked to the dysautonomy score which required a good cooperation of the patient and a great vigilance during its execution. This method could be applied to BP to explore BP regulation in hypertensive subjects.     

Oral contraceptives and rheumatoid arthritis: results from a primary care-based incident case-control study

The influence of celiprolol (beta1- and beta2-adrenoceptor partial agonist), propranolol (beta1- and beta2-adrenoceptor antagonist), and atenolol (beta1-adrenoceptor antagonist) on heart-rate variability (HRV) was assessed from Holter records in 12 normal volunteers. A combination of summary statistics and nonlinear procedures was used to assess HRV and autonomic balance. Under double-blind and randomised conditions (Latin-square design), subjects received placebo, celiprolol (200 and 800 mg), propranolol (160 mg), atenolol (50 mg), and combinations of these agents. Single oral doses of medication (at weekly intervals) were administered at 22:30 h with sleeping heart rates (HRs) recorded overnight. Compared with placebo, celiprolol (200 and 800 mg) increased the sleeping HR, the HR effect of celiprolol was different from the bradycardia after propranolol, 160 mg, and atenolol, 50 mg. Dose-response effects on HR with celiprolol were evident in the presence of atenolol, unlike those with propranolol that abolished the HR increase between celiprolol, 200 mg and 800 mg. These data were consistent with beta1-selective adrenoceptor agonism with 200 mg but agonism at both the beta1- and beta2-adrenoceptor with celiprolol, 800 mg. The action of the drugs on short-term HRV indices (rMSSD and pNN50) closely followed their effects on HR. The longer-term HRV indices (global SD, SDANN) were reduced by celiprolol but increased by propranolol and atenolol. At a fixed HR, the data dispersion (SDNN5) was higher with propranolol compared with celiprolol; however, the dispersion was not merely an HR-dependent phenomenon. A novel nonlinear approach (quadrant analysis) revealed the sequencing of cardiac accelerations and decelerations after the high correlation between adjacent intervals had been removed. Celiprolol increased the frequency of consecutive cardiac accelerations; the duration between and variance of these beat-to-beat differences shortened after celiprolol but lengthened with increased variance after propranolol and atenolol. These results demonstrated reduced HRV indices and a shift toward sympathetic dominance after the beta-adrenoceptor agonist celiprolol contrasting with increased HRV indices and parasympathetic dominance after the beta-adrenoceptor antagonists propranolol and atenolol. The implications of these findings for the treatment of patients with cardiovascular disease warrant further study.     

The role of attentional strategies in moderating links between acute pain induction and subsequent psychological stress: Evidence for symptom-specific reactivity among patients with chronic pain versus healthy nonpatients.

Vulnerability to stressors after pain may depend on the degree to which the strategy used to process information about pain perpetuates thoughts of suffering and distress. Patients with chronic low back pain (CLBP) may show susceptibility to stress after pain through symptom-specific (lower paraspinal [LP]) muscle reactivity. Patients with CLBP (n = 100) and healthy nonpatients (n = 105) underwent a cold pressor, under sensory focus, distraction, suppression, or control conditions, and then performed mental arithmetic. Only patients under the suppression condition revealed increased LP tension during pain that was sustained during mental arithmetic and sustained systolic blood pressure after mental arithmetic. Patients with CLBP who suppress pain may detrimentally affect responses to the next noxious event, particularly through prolonged LP muscle tension, that may contribute to a cycle of pain-stress-pain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rhythms in the central nervous system and 1/f fluctuations of the heart rate

We have developed a system to analyze heart rate variability (HRV) (power spectral array of the HRV) during 24 h ambulatory electrocardiographic monitoring. Several rhythms (circadian and several ultradian rhythms) were observed in the power spectral array of the heart rates and 1/f-like fluctuations in the log-log scaled heart rate power spectrum. The circadian change of the heart rate is closely related to the body temperature rhythm. The 90 min rhythm of HRV during sleep was suspected to be produced by the sleep cycle (REM/NREM) and the lower frequency peak of the HRV was coherent with oscillation in amplitude modulated respiration. These circadian and ultradian rhythm as assessed by heart rate variability exist both in normal subjects and in patients with autonomic failure. The power of the high frequency band decreases in subjects with autonomic failure. The power of low frequency components increases during periodic breathing or Cheyne-Stokes respiration. Log-log scaled analysis of the power spectrum of HRV disclosed that the slope of the HRV is markedly modulated by the range of the frequency applied for the least square regression line analysis. The increased power that might be produced by periodic breathing and decreased power in patients with autonomic failure might strongly modulate the slope of the log-log scaled HRV. It is concluded that the power spectral array of the HRV during 24 h period is useful in the detection of circadian and ultradian rhythm, and log-log scaled power spectra might be useful in the overall integration of the heart rate dynamics produced by the central nervous system. The several rhythm factors that might be produced by the central nervous system might modulate 1/f fluctuations of the HRV.     

Acute exercise: Buffering psychosocial stress responses in women.

48 25–40 yr old women participated in 2 counterbalanced experimental conditions: an attention control and a 40-min bout of aerobic exercise (AE) at 70% heart rate (HR) reserve. The attention control and AE treatments were followed by (1) 30 min of quiet rest, (2) exposure to mental and interpersonal threat, and (3) 5 min of recovery. Blood pressure (BP) and HR were monitored at baseline, during the stressors, and throughout recovery. Self-reported distress was assessed before each stressor and upon completion of the recovery period. Results provide clear evidence that exercise dampened BP reactivity to psychosocial stress. Compared with the attention placebo control, AE reduced both the frequency and intensity of anxiety-related thoughts that occur in anticipation of interpersonal threat and challenge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ouabain effects on activated lymphocytes: augmentation of CD25 expression on TPA-stimulated cells and of CD69 on PHA-and TPA-stimulated cells

The objective of this study was to compare the baroreflex sensitivity (BRS) assessed by the new, non-invasive, spontaneous sequence method (BRS-sequence) with the Valsalva manoeuvrebased BRS. Fourteen healthy volunteers were studied in the supine position, during 60 degrees head-up tilt (HUT) and during -30 degrees head-down tilt (HDT). Blood pressure and R-R intervals were continuously and non-invasively recorded using a Finapres device. The BRS-sequence was assessed by analysing the slopes of spontaneously occurring sequences of three or more consecutive beats in which systolic blood pressure and R-R interval of the following beat increased or decreased in the same direction in a linear fashion; it was compared with data obtained during the Valsalva manoeuvre in each position. The time and frequency domain indices of R-R interval variability were also evaluated. The mean difference of BRS between the two non-invasive methods was 3.86 ms/mmHg with a standard deviation of 9.14 ms/mmHg. BRS was decreased during HUT and increased during HDT as assessed by both techniques. The changes in BRS were associated with vagal withdrawal and sympathetic activation during HUT and enhancement in the cardiac vagal tone and reduction in the sympathetic activity during HDT. We conclude that the BRS-sequence technique provides a reliable method to study the neural control of the circulation, although the body position in consecutive measurements needs to be standardized.     

"Meta-analysis: statistical alchemy for the 21st century": discussion. A plea for a more balanced view of meta-analysis and systematic overviews of the effect of health care interventions

Ventricular arrhythmias and disturbed autonomic control, as reflected by abnormal heart rate variability (HRV), are related to hemodynamic impairment in chronic heart failure (CHF). We investigated the effects of orally (p.o.) administered isomazole, a new phosphodiesterase (PDE) inhibitor with calcium-sensitizing properties, on hemodynamics, ventricular arrhythmias, and HRV and examined a possible interaction between these parameters. Hemodynamic measurements and ambulatory ECG monitoring were performed in 12 patients with stable CHF class III-IV after single doses of isomazole 5-30 mg. Pulmonary wedge pressure decreased after 5, 10, 20, and 30 mg, but cardiac output, (CO) increased only after the higher doses [20 mg, + 20% (p = 0.031)] of isomazole. HR did not change. Mean arterial and pulmonary artery pressure, (MAP, PAP) decreased significantly in the 10- and 20-mg groups [10 mg, -6% (p = 0.035) and -14% (p < 0.001) respectively; 20 mg, -13% (p = 0.047) and -31% (p = 0.006), respectively]. Isomazole did not exert a significant effect on ventricular arrhythmias in the subsequent 24 h after acute dosing. Analysis of HRV showed that rMSSD and pNN50 (parameters of vagal tone) tended to increase after isomazole administration. Normalized high-frequency power during the day increased from 17.4 to 22.3 nu (p < 0.05), whereas low frequency tended to decrease from 52.7 to 48.2 nu (p = 0.06). Acute isomazole administration improves hemodynamics but has no effect on ventricular arrhythmias. The HRV variability data suggest development of an increase in vagal control of HR, parallel to the acute hemodynamic improvement after isomazole. Withdrawal of vagal control of HR in CHF may be a reversible process.     

Endurance training, overtraining and baroreflex sensitivity in female athletes

We examined heavy training-induced changes in baroreflex sensitivity, plasma volume and resting heart rate and blood pressure variability in female endurance athletes. Nine athletes (experimental training group, ETG) increased intense training (70-90% VO2max) volume by 130% and low-intensity training (< 70% Vo2max) volume by 100% during 6-9 weeks, whereas the corresponding increases in six control athletes (CG) were 5% and 10% respectively. Maximal oxygen uptake (VO2max) in the ETG and CG did not change, but in five ETG athletes VO2max decreased from 53.0 +/- 2.2 (mean +/- SEM) (CI 46.8-59.2) ml kg-1 min-1 to 50.2 +/- 2.3 (43.8-56.6) ml kg-1 min-1 (P < 0.01), indicating overtraining. Baroreflex sensitivity (BRS) measured using the phenylephrine technique and blood pressure variability (BPV) did not change, but the low-frequency power of the R-R interval variability increased in the ETG (P < 0.05). The relative change in plasma volume was 7% in the ETG and 3% in the CG. The changes in BRS did not correlate with the changes in plasma volume, heart rate variability and BPV. We conclude that heavy endurance training and overtraining did not change baroreflex sensitivity or BPV but significantly increased the low-frequency power of the R-R interval variability during supine rest in female athletes as a marker of increased cardiac sympathetic modulation.     

Association between aerobic capacity and carotid-cardiac baroreflex responsiveness in women

The purpose of this study was to determine whether the positive correlation between carotid-cardiac baroreflex responsiveness and aerobic capacity (VO(2)max) that has been reported in men also occurs in women. Carotid-cardiac baroreflex responsiveness was tested in 40 healthy, normotensive women (age 18-35) using the variable neck pressure technique. Participants were subdivided into endurance-trained (ET; n = 11) and untrained (UT; n = 9) groups. No significant between-group difference was found in the range or gain of the carotid-cardiac baroreflex response despite a lower resting HR in the ET group. When participants were subdivided into high (HI; n = 13) and low (LO; n = 17) responders based on reflex RRI responses to CTP changes, no significant between-group differences were found in resting HR or VO(2)max levels. It was concluded that aerobic capacity (VO(2)max) is not a good predictor of cardiac-carotid baroreflex responsiveness in healthy women.     

Age-related differences in cardiovascular reactions to mental stress tests in women.

Tested 84 healthy, sedentary women in the laboratory during performance of difficult and easy problem-solving tasks. Ss were divided into 3 equal age groups: 19–32 yrs, 33–43 yrs, and 44–60 yrs. Baseline systolic blood pressure (SBP) and diastolic blood pressure increased with age, whereas skin conductance level was lower in older Ss. Initial SBP reactions to tasks were positively related to age, even after controlling for baseline blood pressure, aerobic fitness, and Framingham Type A Scale (S. G. Haynes et al; see PA, Vol 68:10702) behavior scores. There were no differences in heart rate (HR) or additional HR reactions, so the anticipated decline in cardiac sympathetic response with age was not observed. Mechanisms underlying age-related reactions to mental stress are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

DNA single strand breakage, DNA adducts, and sister chromatid exchange in lymphocytes and phenanthrene and pyrene metabolites in urine of coke oven workers

During heart transplantation (HTX) all neural connections are severed. In humans, signs of autonomic reinnervation have been found. In this study non-invasive tests were used to compare signs of sympathetic and parasympathetic reinnervation. Non-invasive autonomic function tests and heart rate variability parameters (HRV; 24 h electrocardiographic registration) were used to investigate signs of reinnervation. 16 HTX patients (14 males) were compared with age-and sex-matched controls. Parasympathetic heart rate changes in HTX compared to controls were attenuated during the diving test, deep breathing, the Valsalva maneuver and standing up but not during carotid sinus massage. Sympathetic heart rate increases were lower during the cold pressor test and mental stress. The blood pressure responses were comparable to the control group, but not during active standing and tilting. This finding suggests an obligatory 'blood pressure' role for the innervated heart in these two tests. All HRV parameters were lower in HTX. One or more normal parasympathetic responses were found in 13 out of 16 patients versus 4 out of 16 with normal sympathetic responses (p < 0.05). Heart rate variations were less in case of a higher donor age, and higher in case of a longer time after HTX. Parasympathetic signs of reinnervation are more common than sympathetic signs of reinnervation. A higher donor age reduces signs of reinnervation. If the sympatho-vagal balance is a prognostic factor in HTX patients as it is in other cardiac diseases these findings are clinically relevant.     

The relationship between socioeconomic status, hostility, and blood pressure reactions to mental stress in men: Data from the Whitehall II study.

This study investigated the relationship among blood pressure reactions to mental stress, cynical hostility, and socioeconomic status (SES) in 1,091 male public servants. Occupational grade served to index SES and cynical hostility was assessed using the Cook-Medley scale. (Cook & Medley, 1954). The magnitude of systolic, but not diastolic, blood pressure change scores to stress was positively associated with occupational grade: the higher the grade, the greater the reactions. Mental stress task performance also varied with occupational grade but was unrelated to reactivity. Ratings of task difficulty did not vary with occupational grade. Cynical hostility was negatively related to occupational grade, and, contrary to previous findings, negatively related to systolic blood pressure reactivity. Cynical hostility was also negatively related to mental stress task performance but unrelated to ratings of task difficulty. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hypocapnia and cerebral hypoperfusion in orthostatic intolerance

BACKGROUND AND PURPOSE: Orthostatic and other stresses trigger tachycardia associated with symptoms of tremulousness, shortness of breath, dizziness, blurred vision, and, often, syncope. It has been suggested that paradoxical cerebral vasoconstriction during head-up tilt might be present in patients with orthostatic intolerance. We chose to study middle cerebral artery (MCA) blood flow velocity (BFV) and cerebral vasoregulation during tilt in patients with orthostatic intolerance (OI). METHODS: Beat-to-beat BFV from the MCA, heart rate, CO2, blood pressure (BP), and respiration were measured in 30 patients with OI (25 women and 5 men; age range, 21 to 44 years; mean age, 31.3+/-1.2 years) and 17 control subjects (13 women and 4 men; age range, 20 to 41 years; mean age, 30+/-1.6 years); ages were not statistically different. These indices were monitored during supine rest and head-up tilt (HUT). We compared spontaneous breathing and hyperventilation and evaluated the effect of CO2 rebreathing in these 2 positions. RESULTS: The OI group had higher supine heart rates (P<0.001) and cardiac outputs (P<0.01) than the control group. In response to HUT, OI patients underwent a greater heart rate increment (P<0.001) and greater reductions in pulse pressure (P<0.01) and CO2 (P<0.001), but total systemic resistance failed to show an increment. Among the cerebrovascular indices, all BFVs (systolic, diastolic, and mean) decreased significantly more, and cerebrovascular resistance (CVR) was increased in OI patients (P<0.01) compared with control subjects. In both groups, hyperventilation induced mild tachycardia (P<0.001), a significant reduction of BFV, and a significant increase of CVR associated with a fall in CO2. Hyperventilation during HUT reproduced hypocapnia, BFV reduction, and tachycardia and worsened symptoms of OI; these symptoms and indices were improved within 2 minutes of CO2 rebreathing. The relationships between CO2 and BFV and heart rate were well described by linear regressions, and the slope was not different between control subjects and patients with OI. CONCLUSIONS: Cerebral vasoconstriction occurs in OI during orthostasis, which is primarily due to hyperventilation, causing significant hypocapnia. Hypocapnia and symptoms of orthostatic hypertension are reversible by CO2 rebreathing.