Cardiac vagal control and dynamic responses to psychological stress among patients with coronary artery disease

An investigation of vago-regulatory and health-behavior accounts for increased inflammation in posttraumatic stress disorder

OBJECTIVE

Posttraumatic stress disorder (PTSD) has been linked to chronic inflammation, a condition that poses a risk for cardiovascular disease. Attenuated vagal activity has been proposed as a potential mediator of PTSD and inflammation, although associated behavioral health risks-namely cigarette smoking and alcohol dependence-might also account for that link.

METHODS

Inflammation was quantified by fasting serum concentrations of C-reactive protein (CRP), tumor necrosis factor (TNF)-α, interleukin (IL)-10, and thymus- and activation-regulated chemokine (TARC)/CCL17 collected from 85 participants with PTSD and 82 without PTSD. Latent variable modeling was used to assess the relationship between PTSD symptom severity and inflammation along with potential mediators vagal activity (respiratory sinus arrhythmia; RSA), smoking status, and lifetime alcohol dependence.

RESULTS

PTSD symptom severity was associated with increased inflammation (β=.18, p=.02). However, this association was reduced in models that adjusted for RSA, smoking status, and lifetime alcohol dependence. Independent mediation effects were deemed significant via bootstrapping analyses. Together, RSA, smoking status, and lifetime alcohol dependence accounted for 95% of the effect of PTSD symptom severity on inflammation.

CONCLUSION

Although RSA accounted for a modest proportion of the association between posttraumatic stress and pro-inflammatory responses, behavioral factors-specifically cigarette smoking and alcohol dependence-proved to be larger mediators. The benefits of PTSD treatment may be enhanced by additional interventions aimed at modifying these health behaviors.

Interaction of Biological Stress Recovery and Cognitive Vulnerability for Depression in Adolescence

Major Depressive Disorder is a common mental illness with rates increasing during adolescence. This has led researchers to examine developmental antecedents of depression. This study examined the association between depressive symptoms and the interaction between two empirically supported risk factors for depression: poor recovery of the biological stress system as measured through heart rate and cortisol, and cognitive vulnerabilities as indexed by rumination and a negative cognitive style. Adolescents (n = 127; 49 % female) completed questionnaires and a social stress task to elicit a stress response measured with neuroendocrine (cortisol) and autonomic nervous system (heart rate) endpoints. The findings indicated that higher depressive symptoms were associated with the combination of higher cognitive vulnerabilities and lower cortisol and heart rate recovery. These findings can enhance our understanding of stress responses, lead to personalized treatment, and provide a nuanced understanding of depression in adolescence.

C-reactive protein and vulnerability to mental stress-induced myocardial ischemia

Myocardial ischemia provoked in the laboratory during mental stress (MSI) in patients with stable coronary artery disease (CAD) predicts subsequent clinical events. The pathophysiology of MSI differs from that of exercise ischemia, and the mechanisms tying MSI to poor prognosis are not known. C-reactive protein (CRP) is a risk marker for cardiovascular events in patients with CAD, but little is known regarding the relationship of CRP to MSI. The purpose of this study was to examine the association of CRP to risk of MSI in CAD patients. Eighty-three patients with stable CAD underwent simultaneous single-photon emission computed tomography (SPECT) imaging with technetium-99m tetrofosmin myocardial perfusion imaging (MPI) and transthoracic echocardiography (TTE), at rest and during MS induced by laboratory mental stress. Serum CRP levels were measured 24 h after MS. MSI was defined by the presence of a new perfusion defect on SPECT and/or new regional wall motion abnormality on TTE during MS. Of the 83 patients, 30 (36%) developed MSI. There was no difference in gender, sex, BMI, histories of diabetes, hypertension, smoking, lipid profile, medications used (including statins, beta-blockers, ACE inhibitors, and aspirin), or hemodynamic response during MS between those with and without MSI. In univariate logistic regression analysis, each unit (1 mg/L) increase in CRP level was associated with 20% higher risk of MSI (OR 1.2, 95% CI 1.01-1.39, P=.04). This relationship remained in multivariate models. These data suggest that levels of CRP may be a risk marker for MSI in patients with CAD.

C-reactive protein and vulnerability to mental stress-induced myocardial ischemia

Myocardial ischemia provoked in the laboratory during mental stress (MSI) in patients with stable coronary artery disease (CAD) predicts subsequent clinical events. The pathophysiology of MSI differs from that of exercise ischemia, and the mechanisms tying MSI to poor prognosis are not known. C-reactive protein (CRP) is a risk marker for cardiovascular events in patients with CAD, but little is known regarding the relationship of CRP to MSI. The purpose of this study was to examine the association of CRP to risk of MSI in CAD patients. Eighty-three patients with stable CAD underwent simultaneous single-photon emission computed tomography (SPECT) imaging with technetium-99m tetrofosmin myocardial perfusion imaging (MPI) and transthoracic echocardiography (TTE), at rest and during MS induced by laboratory mental stress. Serum CRP levels were measured 24 h after MS. MSI was defined by the presence of a new perfusion defect on SPECT and/or new regional wall motion abnormality on TTE during MS. Of the 83 patients, 30 (36%) developed MSI. There was no difference in gender, sex, BMI, histories of diabetes, hypertension, smoking, lipid profile, medications used (including statins, beta-blockers, ACE inhibitors, and aspirin), or hemodynamic response during MS between those with and without MSI. In univariate logistic regression analysis, each unit (1 mg/L) increase in CRP level was associated with 20% higher risk of MSI (OR 1.2, 95% CI 1.01-1.39, P=.04). This relationship remained in multivariate models. These data suggest that levels of CRP may be a risk marker for MSI in patients with CAD.

The efficacy of behavioral treatments for hypertension

Evidence is reviewed for the efficacy of behavioral treatments for hypertension. The format chosen here is a review of reviews given that numerous consensus committee reports and quantitative reviews on the topic have been published. Extensive evidence from over 100 randomized controlled trials indicates that behavioral treatments reduce blood pressure (BP) to a modest degree, and this change is greater than what is seen in wait-list or other inactive controls. Effect sizes are quite variable. The observed BP reductions are much greater when BP levels were high at pre-test, and behavioral studies tend to underestimate possible benefits because of floor effects in their protocols. Blood pressure measured in the office may be confounded with measurement habituation. Multi-component, individualized psychological treatments lead to greater BP changes than do single-component treatments. Among biofeedback treatments, thermal feedback and electrodermal activity feedback fare better than EMG or direct BP feedback, which tend to produce null effects. There continues to be a scarcity of strong protocols that properly control for floor effects and potential measurement confounds.

Effects of lifestyle modification on the progression of coronary atherosclerosis, autonomic function, and angina--the role of GNB3 C825T polymorphism

BACKGROUND

Given the multimodal medical and interventional treatment options in coronary artery disease, the additional value of intensified lifestyle modification is unclear. We have therefore examined the effects of lifestyle modification on top of current treatment and also associated with the GNB3 C825T polymorphism, which has established association to sympathetic activation and the precipitation of angina.

METHODS

One hundred one patients with established coronary artery disease were randomized to a 1-year lifestyle modification group (lifestyle group [LG]) or an advice group. Risk factors, coronary calcification (electron beam tomography), heart rate variability, baroreflex sensitivity, anginal symptoms, and quality of life (QOL) were assessed on entry and after 1 year.

RESULTS

Patients in LG had excellent program adherence, but lifestyle modification had no impact on metabolic risk factors and coronary calcification. Changes in heart rate, heart rate variability, and blood pressure were only slightly favoring LG. Baroreflex sensitivity increased by 2 (0.79-3.13) ms/mm Hg in the LG but decreased by -0.10 (-1.11 to 0.92) in the advice group (P = .013). Lifestyle modification led to improved physical QOL, reductions of anginal attacks (-54% vs 11%, P = .01), and dose reductions in 30% of anti-ischemic medications (P = .004). *825T allele carriers had a more pronounced reduction of heart rate and improvement of angina and QOL. The beneficial effect on reduction of medication was seen in *825T allele carriers only.

CONCLUSIONS

In the presence of modern treatments, comprehensive lifestyle modification provides no additional benefits on progression of atherosclerosis but improves autonomic function, angina, and QOL with concomitant reduced need of medication. These responses are more pronounced in GNB3*825T allele carriers.

Effects of daily stress on autonomic cardiac control in patients with coronary artery disease

Emotional stress has been implicated in the development and progression of coronary artery disease, with 1 proposed causal pathway being changes in cardiac autonomic tone. One hundred thirty-five patients with coronary artery disease underwent 48 hours of ambulatory electrocardiographic monitoring and completed activity and mood diaries every 20 minutes while awake. Random-effects model analyses associated higher levels of negative emotions (e.g., anger, stress, sadness) with decreases in high- and low-frequency power, whereas higher levels of positive emotion were related to an increase in low-frequency power, independent of age, posture, and medications.

Enhanced heart rate variability and baroreflex index after stress and cholinesterase inhibition in mice

Experiments tested the effect of stress coupled with cholinesterase inhibition on blood pressure, heart rate, baroreflex index, and variability in time and frequency domain in conscious mice. The objective was to determine whether cholinergic systems interact with stress to alter cardiovascular responses. Male C57BL/6J mice with arterial catheters were exposed to 3-day treatments: 1) intermittent shaker stress, 2) pyridostigmine (10 mg.kg(-1).day(-1)); or 3) combined pyridostigmine and stress. Pyridostigmine reduced blood cholinesterase (-33%) with no added effects of stress. Twenty-four-hour blood pressure recordings showed that there were no differences in blood pressure and heart rate with the treatments. Pulse interval standard deviation was greatly increased in the pyridostigmine/stress group compared with stress or pyridostigmine groups (11.0 +/- 1.4, 5.0 +/- 0.9, and 7.5 +/- 0.9 ms, respectively). Spectral analysis showed two distinct components for pulse interval variability (low and high frequency). Variability in the low-frequency range was greatly enhanced in the pyridostigmine/stress group, seen as a doubling of the power (9.5 +/- 1.7, 3.3 +/- 0.9, and 5.0 +/- 0.6 ms for pyridostigmine/stress, stress and pyridostigmine groups, respectively). Baroreflex sensitivity was also increased in the pyridostigmine/stress group (3.6 +/- 0.5 compared with 1.8 +/- 0.3 and 1.7 +/- 0.5 ms/mmHg in the stress and pyridostigmine groups, respectively). There was no difference in blood pressure variability or its spectral components. Results demonstrate that there are potent interactions between a mild stressor and cholinesterase inhibition seen as an accentuation of low-frequency variability in pulse interval time series, probably associated with baroreflex input and autonomic drive.

Adverse effects associated with physical restraint

OBJECTIVE

Restraint use is not monitored in the US, and only institutions that choose to do so collect statistics. In 1999, investigative journalists reported lethal consequences proximal to restraint use, making it a life-and-death matter that demands attention from professionals. This paper reviews the literature concerning actual and potential causes of deaths proximal to the use of physical restraint.

METHOD

Searching the electronic databases Medline, Cinahl, and PsycINFO, we reviewed the areas of forensics and pathology, nursing, cardiology, immunology, psychology, neurosciences, psychiatry, emergency medicine, and sports medicine.

CONCLUSIONS

Research is needed to provide clinicians with data on the risk factors and adverse effects associated with restraint use, as well as data on procedures that will lead to reduced use. Research is needed to determine what individual risk factors and combinations thereof contribute to injury and death.

Predicting blood pressure reactivity and heart rate variability from mood state following coronary artery bypass surgery

STUDY OBJECTIVES

Coronary Artery Bypass Graft (CABG) surgery is a common and successful procedure for revascularisation. However, the experience can induce emotional reactions prior to and following surgery. This study aimed to document changes in blood pressure (BP) reactivity and heart rate variability (HRV) following CABG surgery, and to determine the impact of mood state, particularly anxiety and depression upon cardiovascular functioning.

METHOD

Twenty-two patients preparing to receive elective, first time CABG surgery were recruited from The Cardiothoracic Centre, Liverpool, UK and psychologically assessed using the Hospital Anxiety and Depression Scale (HAD), Global Mood Scale (GMS) and the Dispositional Resilience Scale (DRI). BP and heart rate responses were also measured during four conditions: baseline response; laboratory session; ambulatory monitoring; and self-initialised recordings during the ambulatory period. In addition, HRV was measured for 12 h in conjunction with the ambulatory monitoring period. All measures were assessed 1 week prior to surgery and 2 months following surgery.

RESULTS

A significant decrease in negative mood and an increase in positive mood were reported following surgery. Forty percent of patients were clinically anxious and depressed prior to surgery although this was reduced to 27% after surgery. Depression was the strongest independent predictor of pre-operative BP and HRV whilst anxiety was most significantly related to follow-up BP reactivity. DBP was most strongly predicted by mood state.

CONCLUSIONS

These results suggest that patients with higher levels of anxiety and depression are at risk of reduced HRV and increased BP reactivity in response to mental stressors. The study also strongly suggests that current patient services should be expanded to acknowledge the role of psychological factors within clinical prognosis after CABG surgery.

Cardiovascular reactivity to psychological challenge: conceptual and measurement considerations

OBJECTIVE AND METHODS

This article is a selective review of recent findings bearing on the conceptualization and measurement of cardiovascular reactivity to psychological challenge, with a focus on several issues relevant to the reliability, content validity, construct validity, and criterion validity of these measures.

RESULTS AND CONCLUSIONS

With respect to reliability, use of standardized task demands and aggregated scores are associated with enhanced short-term reliability, but the long-term reliability of cardiovascular reactivity has not been sufficiently documented. With respect to content validity, existing evidence suggests that "vascular" or "cardiac" tasks may evoke responses that reflect similar distributions of individual difference, whereas associations between responses to "physical" and "psychological" tasks are modest. The evidence is not clear at present with respect to the importance of including affective or interpersonal stimuli as part of trait reactivity assessments. With respect to construct validity, existing data show that cardiovascular reactivity to psychological challenge is largely independent of standard measures of autonomic function. With respect to criterion validity, recent studies point to a number of methodological limitations that may have restricted our ability to detect lab-to-life generalizability of reactivity measures in the past. Continued progress in understanding and measuring reactivity as an individual difference dimension is essential in helping us to evaluate emerging evidence examining the relationship between reactivity and disease risk.

Vagal rebound during resolution of tearful crying among depressed and nondepressed individuals

Respiratory sinus arrhythmia (RSA) is an index of the vagal control of heart rate that is associated with emotion regulatory capacity. To examine RSA in depressed and nondepressed participants in the context of an emotion-regulatory challenge, we presented a sad film to induce crying, a behavior associated with heightened parasympathetic activation. We predicted that nondepressed persons who cried would show elevations in RSA during the onset and the resolution of crying. By contrast, we predicted that depressed individuals who cried would fail to exhibit increased RSA over the course of their crying episodes. As hypothesized, nondepressed participants exhibited RSA increases that accompanied the resolution of tearful crying, consistent with a homeostatic function for crying, whereas depressed subjects who cried did not exhibit increased RSA. Results suggest that the physiological self-regulatory mechanisms invoked by crying are compromised in depression.

Social anxiety and response to touch: incongruence between self-evaluative and physiological reactions

Touch is an important form of social interaction, and one that can have powerful emotional consequences. Appropriate touch can be calming, while inappropriate touch can be anxiety provoking. To examine the impact of social touching, this study compared socially high-anxious (N=48) and low-anxious (N=47) women's attitudes concerning social touch, as well as their affective and physiological responses to a wrist touch by a male experimenter. Compared to low-anxious participants, high-anxious participants reported greater anxiety to a variety of social situations involving touch. Consistent with these reports, socially anxious participants reacted to the experimenter's touch with markedly greater increases in self-reported anxiety, self-consciousness, and embarrassment. Physiologically, low-anxious and high-anxious participants showed a distinct pattern of sympathetic-parasympathetic coactivation, as reflected by decreased heart rate and tidal volume, and increased respiratory sinus arrhythmia, skin conductance, systolic/diastolic blood pressure, stroke volume, and respiratory rate. Interestingly, physiological responses were comparable in low and high-anxious groups. These findings indicate that social anxiety is accompanied by heightened aversion towards social situations that involve touch, but this enhanced aversion and negative-emotion report is not reflected in differential physiological responding.

The somatic symptom paradox in DSM-IV anxiety disorders: suggestions for a clinical focus in psychophysiology

Although DSM-IV criteria for anxiety disorders include physiological symptoms, these symptoms are evaluated exclusively by verbal report. The current review explores the background for this paradox and tries to demonstrate on theoretical and empirical grounds how it could be resolved, providing new insights about the role of psychophysiological measures in the clinic. The three-systems approach to evaluating anxiety argues that somatic measures as well as verbal and behavioral ones are indispensable. However, the low concordance between these domains of measurement impugns their reliability and validity. We argue that concordance can be improved by examining the relationship of variables less global than anxiety and by restriction to specific anxiety disorders. For example, recent evidence from our and other laboratories indicate a prominent role of self-reported and physiologically measured breathing irregularities in panic disorder. Nonetheless, even within a diagnosis, anxiety patients vary radically in which somatic variables are deviant. Thus, in clinical practice, individual profiles of psychological and physiological anxiety responses may be essential to indicate distinct therapeutic approaches and ways of tracking improvement. Laboratory provocations specific to certain anxiety disorders and advances in ambulatory monitoring vastly expand the scope of self-report and physiological measurement and will likely contribute to a refined assessment of anxiety disorders.

Cholinergic stimulation with pyridostigmine blunts the cardiac responses to mental stress

Mental stress may induce myocardial ischemia and ventricular arrhythmia in patients with coronary artery disease, and cholinergic stimulation is a potential protective mechanism. The purpose of this study was to determine the effect of pyridostigmine bromide (PYR), a reversible cholinesterase inhibitor, on the cardiac responses to a mental stress challenge. Twelve healthy young volunteers were submitted to a mental stress test (arithmetic test) 2 hours after the oral administration of either placebo or PYR (45 mg) on two separate days, following a randomized crossover double-blind protocol. Heart rate was reduced after both placebo and PYR (p < 0.05), but the cardiac responses to the mental stress were lower with PYR (p < 0.05): mean RR interval (mean +/- SE)-placebo: 730 +/- 19 msec; PYR: 769 +/- 21 msec; Peak systolic pressure-placebo: 129 +/- 4 mmHg; PYR: 124 +/- 3 mmHg; Peak diastolic pressure-placebo: 92 +/- 3 mmHg; PYR: 89 +/- 4 mmHg; Mean rate-pressure product-placebo: 10,496 +/- 412 bpm x mmHg; PYR: 9,746 +/- 383 bpm x mmHg. In conclusion, 45 mg of pyridostigmine blunted the pressor and chronotropic responses to mental stress in healthy young subjects.

Heart rate variability: origins, methods, and interpretive caveats

Components of heart rate variability have attracted considerable attention in psychology and medicine and have become important dependent measures in psychophysiology and behavioral medicine. Quantification and interpretation of heart rate variability, however, remain complex issues and are fraught with pitfalls. The present report (a) examines the physiological origins and mechanisms of heart rate variability, (b) considers quantitative approaches to measurement, and (c) highlights important caveats in the interpretation of heart rate variability. Summary guidelines for research in this area are outlined, and suggestions and prospects for future developments are considered.