Effects of mental state on heart rate and blood pressure variability in men and women

Summary. The effect of different mental states on autonomic modulation of the cardiovascular system was assessed in healthy, normotensive men (n=18) and women (n=12). Heart rate variability (HRV), systolic blood pressure variability (BPV) and arterial baroreflex function were assessed during 4 tests at rest ((10 min+5 min recovery)×4):

• 1 Control (spontaneous breathing, (SB)
• 2 Mental distraction (SB+word puzzle)
• 3 Conscious control of breathing (paced at SB rate) and
• 4 Mental stress (SB+computer quiz).

There were no significant gender differences in the responses to the interventions in terms of arterial (spontaneous) baroreflex (SPBX) control of HR, and indices of time and frequency domains of HRV and BPV, with the exception of the sympathetic indicator of HRV (low frequency power/total power; P<0.01) which was lower in women during control and mental stress tests. Conscious control of breathing at SB did not alter HRV, BPV or SPBX in either men or women. Mental distraction and mental stress led to decreases in indices of time and frequency domains of HRV and BPV in all subjects, as well as increases in HR during distraction and in systolic BP during stress. These findings suggest that in studies of cardiovascular control:

• 1 Paced breathing at SB can be used for individuals with irregular breathing patterns
• 2 The extent of mental stress achieved is intervention-specific and for the most part, independent of gender and
• 3 Resting assessment of HRV, BPV and SPBX can be made by having subjects sit quietly without interventions in a controlled laboratory setting.

     

Metabolic syndrome is associated with decreased heart rate variability in a sex‐dependent manner: a comparison between 252 men and 249 women

Impaired heart rate variability (HRV) is associated with increased risk of cardiovascular disease, but evidence regarding alterations of HRV in metabolic syndrome (MetS) remains elusive. In order to examine HRV in MetS, we subjected 501 volunteers without atherosclerosis, diabetes or antihypertensive medication, mean age 48 years, to passive head‐up tilt. The subjects were divided to control men (n = 131), men with MetS (n = 121), control women (n = 191) and women with MetS (n = 58) according to the criteria by Alberti et al. (Circulation, 2009, 120, 1640). In unadjusted analyses (i) men and women with MetS had lower total power and high‐frequency (HF) power of HRV than controls whether supine or upright (P<0·05 for all). (ii) Supine low‐frequency (LF) power of HRV was lower in men (P = 0·012) but not in women (P = 0·064) with MetS than in controls, while men and women with MetS had lower upright LF power of HRV than controls (P <0·01 for both). (iii) The LF:HF ratio did not differ between subjects with and without MetS. After adjustment for age, smoking habits, alcohol intake, height, heart rate and breathing frequency, only the differences in upright total power and HF power of HRV between women with MetS and control women remained significant (P<0·05). In conclusion, reduced total and HF power of HRV in the upright position may partially explain why the relative increase in cardiovascular risk associated with MetS is greater in women than in men. Additionally, the present results emphasize that the confounding factors must be carefully taken into consideration when evaluating HRV.     

Sympathetic predominance of cardiovascular regulation during mild orthostatic stress in adolescents with chronic fatigue

Haemodynamic abnormalities have been documented in the chronic fatigue syndrome (CFS), indicating functional disturbances of the autonomic nervous system responsible for cardiovascular control. This study was designed to explore the pathophysiology in adolescent CFS-patients by analysing RR-interval (RRI) variability and diastolic blood pressure (DBP) variability during mild orthostatic stress, using an algorithm which accounts for non-stationary biosignals. A total of 27 adolescents with CFS and 33 healthy control subjects having equal age- and sex distribution underwent 15 min of 20 degrees head-up tilt (HUT). The spectral power densities of RRI and DBP were computed in the low-frequency (LF) band (0.04-0.15 Hz) and the high-frequency (HF) band (0.15-0.4 Hz) using an adaptive autoregressive algorithm to obtain a time-varying spectrum. RMSSD, a time domain index of RRI variability, was also computed. At rest, all indices of variability were similar in the two groups. During tilt, CFS patients had a larger increase in the LF/HF ratio (P相似文献   

Taichiquan acutely increases heart rate variability

A group of 15 elderly men and 14 young male students of physical education made twice a series of Taichiquan (TCQ) practices. Their electrocardiograms were recorded on tape-recorder and heart rates and heart rate variability (HRV) were calculated from digitized data. Here we report the results of recordings in supine positions before and after the first and second series of TCQ. Intervals between heart beats (RRIs) and their standard deviation (SDNN) increased in older men from recordings before the exercise to postexercise. In young subjects the SDNN and total variance (TV) of RRIs increased. HRV increases immediately after TCQ-exercise in young and old male healthy subjects. Whether these practices have permanent effects and effects in patients need controlled and prospective studies.     

Effects of endurance training on heart rate and blood pressure variability

Purpose: To study the influences of a 1‐year controlled, randomized endurance exercise training period on heart rate (HR) and blood pressure variability in a representative sample of Finnish men in their late middle age. Methods and results: Subjects were 140 sedentary men aged 53–63 years. The men were randomized into two identical groups: an intervention (EX) and a reference (CO) group. One hundred and twelve of them remained in the final analysis (EX: n=59, CO: n=53). EX trained for 30–60 min three to five times a week with the intensity of 40–60% of maximal oxygen consumption. In EX, 1 year of regular exercise training increased oxygen consumption at respiratory compensation threshold by 11% (P ≤ 0·001) in a maximal cardiorespiratory test. Total power and very low frequency power of R–R interval variability (ms²) tended to increase in the EX group by 26 and 42% and to decrease in the CO group by 13 and 10% (interaction P<0·05 and P<0·01), respectively. There were no significant changes in blood pressure variability. Conclusion: Regular low‐ to moderate‐intensity exercise training could retard the decli‐ning tendency in cardiac autonomic nervous function in older men during 1 year.     

Cosinor analysis of heart rate variability in ambulatory migraineurs

OBJECTIVE: To clarify whether the circadian rhythm of heart rate variability parameters can be identified in patients with migraine during a headache-free period and to identify any specific pattern of the circadian rhythm of heart rate variability, using time-domain and spectral analysis and cosinor rhythm analysis of heart rate variability during normal daily activity. METHODS: Forty-eight-hour Holter electrocardiograms were recorded for 27 patients with migraine during headache-free periods and 24 healthy controls during free activity. The circadian rhythms of heart rate fluctuation parameters, that is, mean interval, standard deviation, root-mean-square successive differences (RMSSD), %RR50, and low (0. 020 to 0.150 Hz) and high frequency (0.150 to 0.400 Hz) heart rate fluctuations were analyzed with the group mean cosinor method. RESULTS: The group mean cosinor analysis and the acrophase-amplitude analysis demonstrated significant differences in circadian rhythm in SD, RMSSD, %RR50, and high frequency between the group with migraine and controls. The amplitudes of SD, RMSSD, %RR50, and high frequency in the group with migraine were smaller than those in controls, which implied parasympathetic hypofunction in migraineurs. There were no significant differences in the MESOR (midline estimating statistic of rhythms) of the analyzed heart rate parameters except for low frequency. The MESOR of low frequency in the migraineurs was significantly smaller than that in the controls. CONCLUSIONS: Patients with migraine have hypofunction in the parasympathetic nervous system during normal daily activity in the headache-free period.     

Early autonomic dysfunction in patients with diabetes mellitus assessed by spectral analysis of heart rate and blood pressure variability

Patients with diabetes mellitus (DM) often have alterations of the autonomic nervous system (ANS), even early in their disease course. Previous research has not evaluated whether these changes may have consequences on adaptation mechanisms in DM, e.g. to mental stress. We therefore evaluated whether patients with DM who already had early alterations of the ANS reacted with an abnormal regulatory pattern to mental stress. We used the spectral analysis technique, known to be valuable and reliable in the investigation of disturbances of the ANS. We investigated 34 patients with DM without clinical evidence of ANS dysfunction (e.g. orthostatic hypotension) and 44 normal control subjects (NC group). No patients on medication known to alter ANS responses were accepted. The investigation consisted of a resting state evaluation and a mental stress task (BonnDet). In basal values, only the 21 patients with type 2 DM were different in respect to body mass index and systolic blood pressure. In the study parameters we found significantly lower values in resting and mental stress spectral power of mid-frequency band (known to represent predominantly sympathetic influences) and of high-frequency and respiration bands (known to represent parasympathetic influences) in patients with DM (types 1 and 2) compared with NC group (5·3 ± 1·2 ms² vs. 6·1 ± 1·3 ms², and 5·5 ± 1·6 ms² vs. 6·2 ± 1·5 ms², and 4·6 ± 1·7 ms² vs. 6·2 ± 1·5 ms², for resting values respectively; 4·7 ± 1·4 ms² vs. 5·9 ± 1·2 ms², and 4·6 ± 1·9 ms² vs. 5·6 ± 1·7 ms², and 3·7 ± 2·1 ms² vs. 5·6 ± 1·7 ms², for stress values respectively; M/F ratio 6/26 vs. 30/14). These differences remained significant even when controlled for age, sex, and body weight. However, patients with DM type 2 (and significantly higher body weight) showed only significant values in mental stress modulus values. There were no specific group effects in the patients with DM in adaptation mechanisms to mental stress compared with the NC group. These findings demonstrate that power spectral examinations at rest are sufficiently reliable to diagnose early alterations in ANS in patients with DM. The spectral analysis technique is sensitive and reliable in investigation of ANS in patients with DM without clinically symptomatic autonomic dysfunction.     

Spectral analysis of heart rate variability and respiration during sleep in cocaine‐exposed neonates

This study’s objective was to examine the autonomic control of heart rate and respiration during the neonatal period in human infants with prenatal exposure to cocaine. Four‐hour daytime recordings of the electrocardiogram (ECG) were obtained from 15 cocaine‐exposed and 13 non‐exposed full‐term neonates at 2 weeks of age during quiet sleep (QS) and active sleep (AS). For each 1‐min epoch of sleep, the power spectrum of the R‐R intervals was computed from the ECG to obtain the total power (0–2 Hz), and spectral power in the high‐frequency (HFP, 0·3–2 Hz), mid‐frequency (MFP, 0·1–0·2 Hz), and low‐frequency (LFP, 0·03–0·1 Hz) bands. Respiration was also monitored and processed using similar spectral analysis procedures. Cocaine‐exposed neonates showed enhanced heart rate variability reflected by an increase in spectral power across all frequency bands. Spectral power in LFP and MFP was higher in cocaine‐exposed neonates during both sleep states, but only in HFP during QS. There were no respiratory patterning differences between the groups to account for these findings. The index of sympathovagal balance (LFP + MFP)/HFP, showed no differences between the groups. We conclude that infants exposed to cocaine in utero show differences in the modulation of heart rate reflecting an increase in both vagal and sympathetic influences.     

Acute effects of caffeine on heart rate variability in habitual caffeine consumers

During the last years, heart rate variability (HRV) has become a promising risk factor for cardiovascular events. However, the effect of caffeine on HRV in habitual caffeine consumers has barely been investigated. Therefore, we treated 30 male habitual caffeine users in a randomized double-blinded crossover study design with either placebo, 100 or 200 mg caffeine orally and determined parameters of HRV under resting conditions and metronomic breathing. As result, we could not detect significant differences in HRV parameters up to 90 min after drug ingestion. We conclude that modest amounts of caffeine do not reveal negative nor positive effects on HRV within the first 90 min after drug ingestion in young and healthy habitual caffeine consumers. However, further research is necessary to determine the effects of caffeine on HRV in habitual caffeine users, healthy as well as suffering from diabetes, hypertension and postmyocardial infarction.     

On- and off-responses of heart rate to exercise - relations to heart rate variability

During physical exercise, heart rate (HR) increases by parasympathetic withdrawal and increase of sympathetic activity to the heart. HR variability (HRV) in time and frequency domains provides information about autonomic control of the cardiovascular system. Non-linear analysis using the Poincaré plot method is able to reveal supplementary information about cardiac autonomic control. The aim of this study was to determine the association between HRV parameters, the initial increase of HR at the onset of exercise (on-response) and HR decrease in the recovery phase after acute exercise (off-response). HR was continuously monitored in 17 healthy male subjects (mean age: 20.3 +/- 0.2 (SEM) years) at rest (25 min supine; 5 min standing), during exercise (8 min of step test at 70% of maximal power output) and in the recovery phase (30 min supine). HRV analysis in time and frequency domains and evaluation of the Poincaré plot measures (length, widths) were performed on selected segments of HR time series. HR on- and off-responses were quantified using an exponential curve fitting technique. The time constants T(on) and T(off), representing the rate of on- and off-responses to exercise, were computed. Postexercise HRV indices and time constant of on-response - T(on) - to exercise were negatively correlated. From preexercise HRV indices, only Poincaré plot parameters were correlated with T(on). No correlation between HRV indices and parameters of off-response was found. In conclusion, preexercise HRV parameters are not closely correlated with the rate of cardioacceleration at the onset of exercise and cannot predict the rate of HR recovery. On the other hand, postexercise HRV parameters are related to the rate of initial adjustment of HR to exercise referring to the importance of rapid HR on-response for a faster recovery after exercise.     

Acute and training effects of resistance exercise on heart rate variability

Heart rate variability (HRV) has been used as a non‐invasive method to evaluate heart rate (HR) regulation by the parasympathetic and sympathetic divisions of the autonomic nervous system. In this review, we discuss the effect of resistance exercise both acutely and after training on HRV in healthy individuals and in those with diseases characterized by autonomic dysfunction, such as hypertension and fibromyalgia. HR recovery after exercise is influenced by parasympathetic reactivation and sympathetic recovery to resting levels. Therefore, examination of HRV in response to acute exercise yields valuable insight into autonomic cardiovascular modulation and possible underlying risk for disease. Acute resistance exercise has shown to decrease cardiac parasympathetic modulation more than aerobic exercise in young healthy adults suggesting an increased risk for cardiovascular dysfunction after resistance exercise. Resistance exercise training appears to have no effect on resting HRV in healthy young adults, while it may improve parasympathetic modulation in middle‐aged adults with autonomic dysfunction. Acute resistance exercise appears to decrease parasympathetic activity regardless of age. This review examines the acute and chronic effects of resistance exercise on HRV in young and older adults.     

Heart rate and blood pressure variability in cardiac diseases: pharmacological implications

Summary— Even at rest, blood pressure and heart rate fluctuate continuously around their mean values. Considerable interest has recently focused on the assessment of spontaneous fluctuations in heart rate and blood pressure, ie, heart rate and blood pressure variability, using time or frequency domain indexes. Heart rate variability has been extensively studied in cardiovascular disease and has emerged as a valuable parameter for detecting abnormalities in autonomic cardiovascular control, evaluating the prognosis and assessing the impact of drug therapy on the autonomic nervous system in patients with myocardial infarction, congestive heart failure or a heart transplant. In contrast, until the recent development of noninvasive methods for continuous blood pressure recording, blood pressure variability received little attention, and this parameter remains to be evaluated in cardiovascular disease.     

Analogue and digital electrocardiogram recordings in the assessment of heart rate variability

We compared analogue and digital 24-h electrocardiogram (ECG) recordings in the assessment of heart rate variability (HRV) in 41 patients with suspected coronary artery disease. The patients underwent ambulatory ECG recordings simultaneously with analogue (A) (Marquette 8500) and digital (D) (Oxford Medilog FD-3) recorders. Digital ECG recordings were analysed with the Excel Medilog II system (DE) and analogue recordings were analysed with both Marquette (AM) and Excel Medilog II (AE) systems. SDNN, SDANN, rMSSD and pNN₅₀ were calculated for the assessment of time domain measures of HRV, and powers of low (0·04–0·15 Hz) and high (0·15–0·40 Hz) spectral components of HRV for the assessment of frequency domain measures of HRV. Correlations between time domain measures of HRV derived from AM, AE and DE recording and analysis techniques were high (r = 0·803–0·999, P<0·001). SDANN and pNN₅₀ assessed with AM and DE were equal, whereas SDNN and rMSSD values differed slightly but significantly from each other (P<0·01 for both). All time domain measures of HRV assessed with AE differed significantly from AM (P<0·001) and from DE (P<0·01). Correlations between frequency domain measures of HRV derived from AM, AE and DE were also high (r = 0·973–0·992, P<0·001). Despite this, frequency domain measures of HRV assessed with AM, AE and DE differed significantly from each other (P<0·001). In conclusion, when analysed with their own analysis systems, analogue and digital recordings provided almost identical time domain, but not frequency domain, measures of HRV. In addition, analysis of an ECG recording with an analysis system of different manufacturer should be avoided.     

Heart rate variability and baroreflex sensitivity in bilateral lung transplant recipients

The effects of lung afferents denervation on cardiovascular regulation can be assessed on bilateral lung transplantation patients. The high‐frequency component of heart rate variability is known to be synchronous with breathing frequency. Then, if heart beat is neurally modulated by breathing frequency, we may expect disappearance of high frequency of heart rate variability in bilateral lung transplantation patients. On 11 patients and 11 matching healthy controls, we measured R‐R interval (electrocardiography), blood pressure (Portapres^®) and breathing frequency (ultrasonic device) in supine rest, during 10‐min free breathing, 10‐min cadenced breathing (0·25 Hz) and 5‐min handgrip. We analysed heart rate variability and spontaneous variability of arterial blood pressure, by power spectral analysis, and baroreflex sensitivity, by the sequence method. Concerning heart rate variability, with respect to controls, transplant recipients had lower total power and lower low‐ and high‐frequency power. The low‐frequency/high‐frequency ratio was higher. Concerning systolic, diastolic and mean arterial pressure variability, transplant recipients had lower total power (only for cadenced breathing), low frequency and low‐frequency/high‐frequency ratio during free and cadenced breathing. Baroreflex sensitivity was decreased. Denervated lungs induced strong heart rate variability reduction. The higher low‐frequency/high‐frequency ratio suggested that the total power drop was mostly due to high frequency. These results support the hypothesis that neural modulation from lung afferents contributes to the high frequency of heart rate variability.     

Derangement of heart rate variability during a catastrophic earthquake: a possible mechanism for increased heart attacks

At 1:47 AM on September 21, 1999, the middle part of Taiwan was struck by a major earthquake measuring 7.3 on the Richter scale. It has been shown that the mental stress caused by an earthquake could lead to a short- or long-term increase in frequency of cardiac death probably through activation of the sympathetic nervous system. The aim of this study was to investigate the effects of emotional stress on the autonomic system during an actual earthquake. Fifteen patients receiving a 24-hour Holter ECG study starting from 10+/-4 hours before the onset of the earthquake were included for the analysis of time- and frequency-domains of heart rate variability (HRV) at several time periods. A 24-hour Holter study recorded 2-6 months before the earthquake in 30 age- and sex-matched subjects served as the control group. Heart rate and the low frequency (LF) to high frequency (HF) ratio increased significantly after the earthquake and were attributed mainly to the withdrawal of the high frequency component (parasympathetic activity) of HRV. Sympathetic activation was blunted in elderly subjects > 60 years old. The concomitant ST-T depression observed in the Holter study correlated with a higher increment of LF as compared to HF components. The changes observed in HRV recovered completely 40 minutes following the earthquake. The derangement of HRV results from the withdrawal of the parasympathetic component and the arousal of sympathetic activity by the stressful earthquake. However, this autonomic derangement returned towards normal 40 minutes following the earthquake.