Cardiovascular and sympathetic responses to a mental stress task in young patients with hypertension and/or obesity

Association between depressive symptoms and heart rate variability in older patients admitted for rehabilitation: a cross-sectional study

Heart rate variability (HRV) is associated with depressive symptoms, but this relationship in older inpatients undergoing rehabilitation remains unclear. This study investigated the relationship between HRV and depressive symptoms in older inpatients undergoing rehabilitation. Fifty patients aged ≥65 years were assessed for depressive symptoms using the Geriatric Depression Scale. HRV was assessed by frequency analysis. The relationship between depressive symptoms and HRV indices, age, sex, Short Physical Performance Battery (SPPB) score, Mini-Mental State Examination score was examined using simple linear regression. Next, the predictors from the simple linear regression analysis significant at the 0.15 level were inputted in a multiple regression model. Multiple regression analysis revealed that very low frequency HRV [ β = -2.13, 95% confidence interval (CI) -3.15 to -1.11, P  < 0.05] and SPPB score ( β = -0.30, 95% CI -0.52 to -0.08, P  < 0.05) were negatively associated with depressive symptoms: the lower the HRV and the more severe the mobility impairment, the higher the severity of the depressive symptoms. Very low frequency (VLF) HRV and physical performance, as measured by the SPPB score, were associated with depressive symptoms in older patients undergoing rehabilitation. VLF HRV may serve as a useful biomarker for detecting depressive symptoms in this population.

Physiological reactivity to acute mental stress in essential hypertension-a systematic review

Objective

Exaggerated physiological reactions to acute mental stress (AMS) are associated with hypertension (development) and have been proposed to play an important role in mediating the cardiovascular disease risk with hypertension. A variety of studies compared physiological reactivity to AMS between essential hypertensive (HT) and normotensive (NT) individuals. However, a systematic review of studies across stress-reactive physiological systems including intermediate biological risk factors for cardiovascular diseases is lacking.

Methods

We conducted a systematic literature search (PubMed) for original articles and short reports, published in English language in peer-reviewed journals in November and December 2022. We targeted studies comparing the reactivity between essential HT and NT to AMS in terms of cognitive tasks, public speaking tasks, or the combination of both, in at least one of the predefined stress-reactive physiological systems.

Results

We included a total of 58 publications. The majority of studies investigated physiological reactivity to mental stressors of mild or moderate intensity. Whereas HT seem to exhibit increased reactivity in response to mild or moderate AMS only under certain conditions (i.e., in response to mild mental stressors with specific characteristics, in an early hyperkinetic stage of HT, or with respect to certain stress systems), increased physiological reactivity in HT as compared to NT to AMS of strong intensity was observed across all investigated stress-reactive physiological systems.

Conclusion

Overall, this systematic review supports the proposed and expected generalized physiological hyperreactivity to AMS with essential hypertension, in particular to strong mental stress. Moreover, we discuss potential underlying mechanisms and highlight open questions for future research of importance for the comprehensive understanding of the observed hyperreactivity to AMS in essential hypertension.

Effects of Nadishodhana and Bhramari Pranayama on heart rate variability, auditory reaction time, and blood pressure: A randomized clinical trial in hypertensive patients

BACKGROUND

Hypertension (HTN) is a chronic elevation of arterial blood pressure (BP) due to environmental and lifestyle factors. The lifelong treatment protocol causes poor adherence to anti-hypertensive drugs. Nadi Shodhana and Bhramari pranayama are the most effective yogic treatment for the management of HTN.

OBJECTIVES

This study was done to assess and compare the immediate effect of Nadi Shodhana and Bhramari Pranayama on HRV and ART in hypertensive individuals. Thus, to understand the effectiveness of specific pranayama on hypertension.

METHODOLOGY

This study is a randomized, comparative study design. The hundred participants were recruited into two groups 1 (n = 50) and 2 (n = 50). The study was conducted on pre-diagnosed patients with HTN, from the inpatient department of SDM Nature Cure Hospital, Shanthivana. Group 1 was asked to practice Nadi Shodhana Pranayama and Group-2 was asked to practice Bhramari Pranayama for 20 min. The patients were assessed for Heart Rate Variability & Auditory Reaction Time before and immediately after the intervention.

RESULTS

Nadi Shodhana Pranayama showed a significant decrease in ART (p = 0.01) and Bhramari Pranayama showed a highly significant decrease in ART (p < 0.00001). Whereas there was no statistically significant difference in both the groups in HRV parameters.

CONCLUSION

The study showed that both Nadi Shodhana and Bhramari Pranayama can be effective in balancing the sympathovagal tone. Thus, Nadi Shodhana and Bhramari Pranayama can be practised for the management of essential hypertension.

Cardiovascular stress reactivity, habituation, and adiposity

The relationship between adiposity and cardiovascular disease morbidity and mortality is complex. One pathway through which adiposity may influence future health outcomes is by altering how biological systems respond to stress. The current study aimed to examine the association between two metrics of adiposity (body mass index and waist-hip ratio) and two indices of cardiovascular stress responses (reactivity and habituation). A sample of 455 participants (Mean age = 19.47, SD = 1.25 years; BMI = 24.32, SD = 5.04 kg/m² ; 62% female; 17.9% Hispanic/Latino; 65.2% White, 18.7% Asian, 7.9% Black, 0.2% American Indian/Alaska Native, and 7% other) completed two acute psychosocial stress tasks. Heart rate (HR), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were recorded throughout each stressor. In unadjusted and adjusted models, there were no statistically significant associations between adiposity and HR, SBP, or DBP stress reactivity or habituation. The current data do not support the hypothesis that adiposity influences health by altering cardiovascular responses to acute psychological stress. Results are at odds with prior population-level studies and the single prior study examining adiposity and habituation. At the same time, results are in line with mounting evidence that adiposity itself does not drive poor cardiovascular outcomes seen in people classified as overweight or obese.

Hyperreactivity of Salivary Alpha-Amylase to Acute Psychosocial Stress and Norepinephrine Infusion in Essential Hypertension

It is unknown whether the observed general physiological hyperreactivity to acute psychosocial stress in essential hypertension also extends to salivary alpha-amylase (sAA), a surrogate sympathetic nervous system marker. Here, we investigated sAA reactivity to acute psychosocial stress in essential hypertensive males (HT) as compared to normotensive controls (NT). To shed light on underlying mechanisms, we moreover tested for sAA reactivity following a standardized norepinephrine (NE) infusion. We hypothesized that both acute psychosocial stress and an NE infusion of similar duration would lead to greater sAA reactivity in HT than in NT. In the stress study, we examined sAA reactivity to 15 min of acute psychosocial stress induced by the Trier Social Stress Test (TSST) in 19 HT and 23 NT up to 40 min after stress. In the infusion study, 20 HT and 22 NT received a standardized NE infusion (5 μg/mL/min) over 15 min mimicking NE release in reaction to acute psychosocial stress. HT exhibited greater sAA reactivity to the TSST as compared to NT (p = 0.049, ηp2 = 0.08, f = 0.29). In reaction to the standardized NE infusion, HT showed higher sAA reactivity as compared to NT (p = 0.033, ηp2 = 1.00, f = 0.33). Our findings suggest stress-induced sAA hyperreactivity in essential hypertension that seems to be at least in part mediated by a higher reactivity to a standardized amount of NE in HT. With respect to clinical implications, sAA stress reactivity may serve as a noninvasive marker indicative of early cardiovascular risk.

Effects of regular cannabis and nicotine use on acute stress responses: chronic nicotine, but not cannabis use, is associated with blunted adrenocortical and cardiovascular responses to stress

RATIONALE

Cannabis is one of the most prevalent substances used by tobacco smokers and, in light of the growing list of states and territories legalizing cannabis, it is expected that co-use of cannabis and nicotine will escalate significantly and will lead to continuing challenges with tobacco use.

OBJECTIVES

This study was conducted to examine the interactive effects of chronic cannabis and nicotine use on adrenocortical, cardiovascular, and psychological responses to stress and to explore sex differences in these effects.

METHODS

Participants (N = 231) included cannabis-only users, nicotine-only users, co-users of both substances, and a non/light-user comparison group. After attending a medical screening session, participants completed a laboratory stress session during which they completed measures of subjective states, cardiovascular responses, and salivary cortisol during baseline (rest) and after exposure to acute stress challenges.

RESULTS

Nicotine use, but not cannabis use, was associated with blunted cortisol and cardiovascular responses to stress across both men and women. Men exhibited larger cortisol responses to stress than women. Co-users had significantly larger stress-related increases in cannabis craving than cannabis-only users. Cannabis users reported smaller increases in anxiety during stress than cannabis non/light-users, and both male nicotine-only users and male cannabis-only users experienced significantly smaller increases in stress than their non/light-user control counterparts.

CONCLUSIONS

This study replicates and extends earlier research on the impacts of sex and nicotine use on stress responses, and it provides novel findings suggesting that when co-used with nicotine, cannabis use may not confer additional alterations to physiological nor subjective responses to stress. Co-use, however, was associated with enhanced stress-related craving for cannabis.

Association between Depression and Heart Rate Variability in Rehabilitation Ward Patients with Musculoskeletal Dysfunction: A Pilot Study

Objectives:

The purpose of this study was to determine the relationship between depression and heart rate variability (HRV) in rehabilitation ward inpatients.

Methods:

Depression was assessed using the Self-Rating Depression Scale (SDS) in 10 inpatients in a convalescent rehabilitation ward. We also measured R–R intervals during nighttime rest, evaluated HRV by frequency analysis, and confirmed the association between autonomic activity and depression by calculation of Spearman’s rank correlation coefficient.

Results:

A negative correlation was found between depression and the very low-frequency (VLF) band of HRV (ρ=−0.70, P<0.05). SDS showed no significant correlation with low-frequency (LF) band (ρ=−0.32, P=0.36) or high-frequency (HF) band (ρ=−0.21, P=0.46).

Conclusions:

The results of this study suggest that the VLF band of HRV may be an effective indicator of autonomic activity in the evaluation of depression. Further studies are needed to verify the usefulness of the VLF band of HRV as an indicator for detecting depression.

Cardiac autonomic function in patients with early multiple sclerosis

PURPOSE

Cardiac autonomic dysfunction has been reported in patients with long-standing multiple sclerosis (MS); however, data in early disease are limited. The present study was aimed at evaluating cardiac autonomic function in patients with early MS in the context of white matter metabolic status, which could potentially affect functions of the autonomic brain centers.

METHODS

Cardiac sympathetic and baroreflex cardiovagal responses to the Valsalva maneuver, orthostatic test, and the Stroop test were evaluated in 16 early, treatment-naïve patients with relapsing-remitting MS, and in 14 healthy participants. Proton magnetic resonance spectroscopic imaging (MRSI) of the brain was performed in eight of these MS patients and in eight controls.

RESULTS

Valsalva maneuver outcomes were comparable between patients and controls. At baseline, norepinephrine levels were lower (p = 0.027) in MS patients compared to controls. The patients had higher heart rate (p = 0.034) and lower stroke volume (p = 0.008), but similar blood pressure, cardiac output and norepinephrine increments from baseline to 2 min of the orthostatic test compared to controls. MS patients and controls did not differ in responses to the Stroop test. MRSI showed lower total N-acetylaspartate/total creatine (p = 0.038) and higher myo-inositol/total creatine (p = 0.013) in MS lesions compared to non-lesional white matter.

CONCLUSION

Our results show normal cardiac sympathetic and baroreflex cardiovagal function in MS patients with relapsing-remitting MS with lesions at the post-acute/early resolving stage.

TRIAL REGISTRATION

The study was registered at ClinicalTrials.gov under the Identifier: NCT03052595 and complies with the STROBE checklist for cohort, case-control, and cross-sectional studies.

Heart-brain interactions during social and cognitive stress in hypertensive disease: A multidimensional approach

Hypertensive disease (HTD), a prominent risk factor for cardiovascular and cerebrovascular diseases, is characterized by elevated stress-proneness. Since stress levels are underpinned by both cardiac and neural factors, multidimensional insights are required to robustly understand their disruption in HTD. Yet, despite their crucial relevance, heart rate variability (HRV) and multimodal neurocognitive markers of stress in HTD remain controversial and unexplored respectively. To bridge this gap, we studied cardiodynamic as well as electrophysiological and neuroanatomical measures of stress in HTD patients and healthy controls. Both groups performed the Trier Social Stress Test (TSST), a validated stress-inducing task comprising a baseline and a mental stress period. During both stages, we assessed a sensitive HRV parameter (the low frequency/high frequency [LF/HF ratio]) and an online neurophysiological measure (the heartbeat-evoked potential [HEP]). Also, we obtained neuroanatomical data via voxel-based morphometry (VBM) for correlation with online markers. Relative to controls, HTD patients exhibited increased LF/HF ratio and greater HEP modulations during baseline, reduced changes between baseline and stress periods, and lack of significant stress-related HRV modulations associated with the grey matter volume of putative frontrostriatal regions. Briefly, HTD patients presented signs of stress-related autonomic imbalance, reflected in a potential basal stress overload and a lack of responsiveness to acute psychosocial stress, accompanied by neurophysiological and neuroanatomical alterations. These multimodal insights underscore the relevance of neurocognitive data for developing innovations in the characterization, prognosis and treatment of HTD and other conditions with autonomic imbalance. More generally, these findings may offer new insights into heart-brain interactions.

Respiratory Sinus Arrhythmia as an Index of Cardiac Vagal Control in Mitral Valve Prolapse

Respiratory sinus arrhythmia (RSA), i.e. heart rate (HR) variations during inspiration and expiration, is considered as a noninvasive index of cardiac vagal control. Mitral valve prolapse (MVP) could be associated with increased cardiovascular risk; however, the studies are rare particularly at adolescent age. Therefore, we aimed to study cardiac vagal control indexed by RSA in adolescent patients suffering from MVP using short-term heart rate variability (HRV) analysis. We examined 12 adolescents (girls) with MVP (age 15.9±0.5 years) and 12 age and gender matched controls. Resting ECG was continuously recorded during 5 minutes. Evaluated HRV indices were RR interval (ms), rMSSD (ms), pNN50 (%), log HF (ms(2)), peak HF (Hz) and respiratory rate (breaths/min). RR interval was significantly shortened in MVP group compared to controls (p=0.004). HRV parameters-rMSSD, pNN50 and log HF were significantly lower in MVP compared to controls (p=0.017, p=0.014, p= 0.015 respectively). Our study revealed reduced RSA magnitude indicating impaired cardiac vagal control in MVP already at adolescent age that could be crucial for early diagnosis of cardiovascular risk in MVP.

Effects of Auricular Acupressure on Women With Irritable Bowel Syndrome

The purpose of this study was to examine the effect of auricular acupressure on bowel symptoms, stress, mental health, and heart rate variability in women with irritable bowel syndrome (IBS). A quasi-experimental study design with a nonequivalent control group assessed a total sample of 56 women diagnosed with IBS according to Rome III criteria. There were 29 women in the experimental group who received auricular acupressure; 27 women were in the control group. Semen sinapis albae seeds were used to administer acupressure to four auricular points: endocrine, large intestine, lung, and Shenmen for 5 days/week for 4 weeks; the control group received no treatment. Bowel symptoms, stress, mental health, and heart rate variability were measured twice, once before and once after the intervention. Chi-square tests, t tests, and paired t tests were used for analysis. The experimental group had decreased loose stools, abdominal pain, diarrhea, abdominal discomfort, stress, and heart rate variability compared with the control group (p < .05). Auricular acupressure was effective for symptom improvement in patients with IBS.

MEMRI reveals altered activity in brain regions associated with anxiety, locomotion, and cardiovascular reactivity on the elevated plus maze in the WKY vs SHR rats

Individuals with anxiety/depression often have exaggerated cardiovascular responses to stressful stimuli and a comorbidity with hypertension. Alternatively, individuals with hypertension can be more anxious. In the present study cardiovascular changes were evaluated during behavioral testing of anxious behavior on the elevated plus maze (EPM) in the spontaneously hypertensive rat (SHR), a rodent model of neurogenic hypertension, and compared to the response of the more anxious, but normotensive, Wistar-Kyoto rat (WKY). Manganese-enhanced magnetic resonance imaging (MEMRI) was used to identify regional differences in baseline brain activity. Parallel to indicators of elevated behavioral anxiety on the EPM, WKYs had a greater increase in blood pressure but not heart rate when compared to the SHR while on the EPM. Associated with differences in anxiety-related behavior and autonomic responses, we observed increased baseline activity in the amygdala, central gray, habenula and interpeduncular nucleus with MEMRI of the WKY compared to the SHR. Conversely, elevated baseline brain activity was found in regions associated with blood pressure control and system arousal, including the hypothalamus, locus coeruleus and pedunculopontine tegmental nucleus, in the SHR vs WKY, in-line with increased resting blood pressure and increased mobility in this strain. Lastly, reduced activity in hippocampal regions was identified in the SHR compared to the WKY and may be associated with cognitive impairment previously reported in the SHR. Thus, autonomic reactivity may be a true measure of stress in rodent models of anxiety and MEMRI presents a powerful technique to uncover novel brain mechanisms of blood pressure control.

Influence of pre-existing hypertension on neuroendocrine and cardiovascular changes evoked by chronic stress in female rats

This study investigated neuroendocrine, autonomic, and cardiovascular changes evoked by daily exposure to the same type of stressor (homotypic) or different aversive stressor stimuli (heterotypic) in 60-days-old female normotensive Wistar rats and female spontaneously hypertensive rats (SHR). Both strains of rats were exposed for 10 consecutive days to either the homotypic stressor repeated restraint stress (RRS) or the heterotypic stressor chronic unpredictable stress (CUS). As expected, SHR had higher baseline blood pressure values and impaired baroreflex activity in relation to normotensive animals. Besides, SHR presented higher plasma corticosterone levels and decreased thymus weight. Both RRS and CUS increased baseline plasma corticosterone concentration and decreased body weight gain in both normotensive and SHR rats. In addition, both stress protocols caused hypertrophy of adrenal glands in normotensive rats. Regarding the cardiovascular effects, RRS increased basal heart rate in both rat strains, which was mediated by an increase in sympathetic tone to the heart. Besides, RRS increased baroreflex-mediated tachycardia in SHR animals, while CUS increased cardiac parasympathetic activity and pacemaker activity in normotensive rats. Taken together, these results indicate a stress type-specific effect, as identified by a vulnerability of both strains to the deleterious cardiovascular effects evoked by the homotypic stressor and a resilience to the impact of the heterotypic stressor. Vulnerability of hypertensive rats was evidenced by the absence of CUS-evoked adaptive cardiovascular responses and an increase of baroreflex tachycardia in SHR animals subjected to RRS. The somatic and HPA axis changes were overall independent of the chronic stress regimen and pre-existing hypertension.

Autonomic Nervous System Response to Stressors in Newly Diagnosed Patients with Multiple Sclerosis

Autonomic dysfunction is commonly detected in patients with multiple sclerosis (MS). However, data evaluating autonomic nervous system function in early MS are limited. Present study investigates response to two different stressors in newly diagnosed MS patients, looking for the signs of autonomic dysfunction at the beginning of the disease. We examined 19 MS patients and 19 age, sex, and body mass index matched healthy controls. MS patients were newly diagnosed, untreated, and with low expanded disability status scale (EDSS) values [median 1.0 (interquartile range 1.0-1.5)]. Two stressors were used to evaluate the response of autonomic nervous system: Stroop word-color interference mental stress test and orthostasis. Plasma levels of epinephrine and norepinephrine, blood pressure (BP), and heart rate variability (HRV) parameters were evaluated. At the end of Stroop test MS patients had lower systolic BP (121 ± 15 vs. 132 ± 17 mmHg, p = 0.044), lower heart rate (79 ± 9 vs. 88 ± 16 1/min, p = 0.041), and lower epinephrine increment (10 ± 22 vs. 30 ± 38 pg/ml; p = 0.049) compared to healthy controls. Norepinephrine response was unaffected in MS, however, with lower norepinephrine levels during the test (p = 0.036). HRV parameters were similar in both groups. No differences in BP, heart rate, catecholamines, and HRV parameters between groups during orthostatic testing were found. We found slightly diminished sympathetic response to mental stress test, but unchanged response to orthostasis, in newly diagnosed untreated MS patients. The results suggest that autonomic dysfunction in MS is connected with more developed disease.

Blood pressure regulation in stress: focus on nitric oxide-dependent mechanisms

Stress is considered a risk factor associated with the development of various civilization diseases including cardiovascular diseases, malignant tumors and mental disorders. Research investigating mechanisms involved in stress-induced hypertension have attracted much attention of physicians and researchers, however, there are still ambiguous results concerning a causal relationship between stress and long-term elevation of blood pressure (BP). Several studies have observed that mechanisms involved in the development of stress-induced hypertension include increased activity of sympathetic nervous system (SNS), glucocorticoid (GC) overload and altered endothelial function including decreased nitric oxide (NO) bioavailability. Nitric oxide is well known neurotransmitter, neuromodulator and vasodilator involved in regulation of neuroendocrine mechanisms and cardiovascular responses to stressors. Thus NO plays a crucial role in the regulation of the stress systems and thereby in the BP regulation in stress. Elevated NO synthesis, especially in the initial phase of stress, may be considered a stress-limiting mechanism, facilitating the recovery from stress to the resting levels via attenuation of both GC release and SNS activity as well as by increased NO-dependent vasorelaxation. On the other hand, reduced levels of NO were observed in the later phases of stress and in subjects with genetic predisposition to hypertension, irrespectively, in which reduced NO bioavailability may account for disruption of NO-mediated BP regulatory mechanisms and accentuated SNS and GC effects. This review summarizes current knowledge on the role of stress in development of hypertension with a special focus on the interactions among NO and other biological systems affecting blood pressure and vascular function.

Early cognitive impairment along with decreased stress-induced BDNF in male and female patients with newly diagnosed multiple sclerosis

The aim of this study was to evaluate neuroendocrine activation during stress in patients with recently diagnosed multiple sclerosis before starting the immunomodulatory therapy (EDSS score≤2.0). We verified the hypothesis that certain cognitive and affective dysfunction is present already at this early stage of the disease. The sample consisted of 38 subjects, which involved patients who were recently diagnosed multiple sclerosis and age- and sex-matched healthy volunteers. Stroop test served as mental stress model enabling measurement of cognitive performance. Present results showed increased state anxiety, depression scores and poorer performance in the Stroop test in the group of patients compared to healthy subjects. The cognitive dysfunction was particularly evident in male patients with simultaneously decreased concentrations of the brain-derived neurotrophic factor (BDNF) in plasma. The patients at this stage of the disease have not yet developed the hyperactivity of the hypothalamic-pituitary-adrenocortical axis. They showed normal levels of plasma copeptin and reduced aldosterone response to mental stress test in women only. Concentrations of plasma copeptin were higher in men compared to women. Very early stages of multiple sclerosis are accompanied by disturbances in psychological well-being, mild cognitive dysfunction and decreased plasma concentrations of BDNF, particularly in male patients.

Psychosocial stress based on public speech in humans: is there a real life/laboratory setting cross-adaptation?

Repeated or chronic exposure to stressors is associated with changes in neuroendocrine responses depending on the type, intensity, number and frequency of stress exposure as well as previous stress experience. The aim of the study was to test the hypothesis that salivary cortisol and cardiovascular responses to real-life psychosocial stressors related to public performance can cross-adapt with responses to psychosocial stress induced by public speech under laboratory setting. The sample consisted of 22 healthy male volunteers, which were either actors, more precisely students of dramatic arts or non-actors, students of other fields. The stress task consisted of 15 min anticipatory preparation phase and 15 min of public speech on an emotionally charged topic. The actors, who were accustomed to public speaking, responded with a rise in salivary cortisol as well as blood pressure to laboratory public speech. The values of salivary cortisol, systolic blood pressure and state anxiety were lower in actors compared to non-actors. Unlike non-actors, subjects with experience in public speaking did not show stress-induced rise in the heart rate. Evaluation of personality traits revealed that actors scored significantly higher in extraversion than the subjects in the non-actor group. In conclusion, neuroendocrine responses to real-life stressors in actors can partially cross-adapt with responses to psychosocial stress under laboratory setting. The most evident adaptation was at the level of heart rate responses. The public speech tasks may be of help in evaluation of the ability to cope with stress in real life in artists by simple laboratory testing.

Power Spectral Density Analysis of Electrodermal Activity for Sympathetic Function Assessment

Time-domain features of electrodermal activity (EDA), the measurable changes in conductance at the skin surface, are typically used to assess overall activation of the sympathetic system. These time domain features, the skin conductance level (SCL) and the nonspecific skin conductance responses (NS.SCRs), are consistently elevated with sympathetic nervous arousal, but highly variable between subjects. A novel frequency-domain approach to quantify sympathetic function using the power spectral density (PSD) of EDA is proposed. This analysis was used to examine if some of the induced stimuli invoke the sympathetic nervous system's dynamics which can be discernible as a large spectral peak, conjectured to be present in the low frequency band. The resulting indices were compared to the power of low-frequency components of heart rate variability (HRVLF) time series, as well as to time-domain features of EDA. Twelve healthy subjects were subjected to orthostatic, physical and cognitive stress, to test these techniques. We found that the increase in the spectral powers of the EDA was largely confined to 0.045-0.15 Hz, which is in the prescribed band for HRVLF. These low frequency components are known to be, in part, influenced by the sympathetic nervous dynamics. However, we found an additional 5-10% of the spectral power in the frequency range of 0.15-0.25 Hz with all three stimuli. Thus, dynamics of the normalized sympathetic component of the EDA, termed EDASympn, are represented in the frequency band 0.045-0.25 Hz; only a small amount of spectral power is present in frequencies higher than 0.25 Hz. Our results showed that the time-domain indices (the SCL and NS.SCRs), and EDASympn, exhibited significant increases under orthostatic, physical, and cognitive stress. However, EDASympn was more responsive than the SCL and NS.SCRs to the cold pressor stimulus, while the latter two were more sensitive to the postural and Stroop tests. Additionally, EDASympn exhibited an acceptable degree of consistency and a lower coefficient of variation compared to the time-domain features. Therefore, PSD analysis of EDA is a promising technique for sympathetic function assessment.

The Role of the Myocardial Microvasculature in Mental Stress-Induced Myocardial Ischemia

There is increasing evidence that mental stress can manifest as physical diseases. One such condition is mental stress-induced myocardial ischemia (MSIMI); a silent, transient, myocardial ischemic response to stressful conditions. We propose that the cardiac microvasculature may be an important site for the interplay between mental stress and MSIMI. This study is a review of the literature discussing the prevalence and emerging mechanisms underlying MSIMI. We identified several aspects underlying MSIMI, including psychological, genetic, and physiological causes. Several sources suggested that dysfunctional cardiac microvasculature might be a contributing factor in the development of stress-induced myocardial ischemia. The literature also suggested that although MSIMI has distinct features and pathophysiology, its occurrence might indicate an increased future risk of cardiovascular events. We found that dysfunctional cardiac microvasculature may be the key point of interaction between mental stress and transient myocardial ischemia and that the development of MSIMI might be a "silent" indicator for future cardiac events.