Effects of alprazolam and imipramine on parasympathetic cardiac control in patients with generalized anxiety disorder

Effects of Oral Administration of Alprazolam and Lorazepam as Hypnotics on Cardiovascular Parameters in Hypertensive Patients

BACKGROUND

Previous studies have suggested that evening intake of benzodiazepine affects blood pressure (BP) and/or heart rate (HR) in healthy and hypertensive subjects. The aim of this study was to compare the effect of chronic oral administration of alprazolam and lorazepam as hypnotics on ambulatory BP and HR in patients with mild hypertension.

METHODS

Consecutive outpatients of both sexes with newly diagnosed, never-treated mild hypertension were randomized, after a 4-week placebo run-in period, to receive alprazolam 0.5 mg plus placebo, lorazepam 1 mg plus placebo, or placebo plus placebo for 2 weeks in 3 crossover periods, each separated by a 1-week placebo wash-out period. At the end of the initial placebo run-in and of each treatment period, 24-hour ambulatory BP and HR monitoring was performed using a noninvasive device.

RESULTS

In the 32 patients, no treatment had any effect on 24-hour and daytime systolic BP (SBP), diastolic BP (DBP), and HR, which remained unchanged. During the nighttime, SBP and DBP values were unaffected by alprazolam, as compared with placebo, whereas DBP was significantly higher after treatment with lorazepam (+3.7%, P < 0.05 vs placebo). Nocturnal HR mean values were significantly increased by lorazepam (+10.1%, P < 0.01 vs placebo), whereas they did not change after alprazolam.

CONCLUSIONS

In patients with mild hypertension, oral intake of alprazolam or lorazepam as hypnotics did not affect ambulatory BP or HR values. A slight increase in nighttime DBP was observed with lorazepam, whereas alprazolam showed no effect on nocturnal BP and HR, probably reflecting a stimulating effect of the drug on central α2-receptors.

Comparing the efficacy of benzodiazepines and serotonergic anti-depressants for adults with generalized anxiety disorder: a meta-analytic review

INTRODUCTION

Generalized anxiety disorder (GAD) is a common form of anxiety disorder. Selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), and benzodiazepines (BZs) are the most commonly prescribed medications for GAD, but little is known about the relative efficacy of these pharmacological treatments. Areas covered: This study provides a meta-analytic review of the efficacy of these medications in the treatment of adults with GAD. A comprehensive literature search yielded 54 articles reporting 56 unique studies with 12,655 participants treated with either pill placebo (6,191 participants), SSRIs (16 trials, 2,712 participants), SNRIs (17 trials, 2,603 participants), or BZs (23 trials, 1,149 participants). The overall combined effect size was modest to moderate (Hedges' g = 0.37, p < 0.0001). Effect sizes decreased significantly over time. SSRIs (Hedges' g = 0.33) and SNRIs (Hedges' g = 0.36) demonstrated significantly lower effect sizes than BZs (Hedges' g = 0.50). These findings were not due to differences in treatment length or publication year. Expert opinion: The results of this study suggest that the most common forms of pharmacotherapy for adult GAD are moderately effective, with BZs being the most effective drug.

Pharmacological Management of Anxiety Disorders in the Elderly

Anxiety disorders are common in the elderly. Additionally, anxiety symptoms often accompany co-morbid psychiatric, medical, as well as neurodegenerative diseases in the older population. Anxiety in the elderly, often accompanied by depression, can lead to worsening physical, cognitive and functional impairments in this vulnerable population. Antidepressants are considered first line treatment. Both SSRIs and SNRIs are efficacious and well-tolerated in the elderly. Some SSRIs are strong inhibitors of the cytochrome P450 hepatic pathway whereas others have less potential for drug interaction. Those antidepressants with more favorable pharmacokinetic profiles should be considered first-line in the treatment of anxiety. Mirtazapine and vortioxetine are also considered safe treatment options. Buspirone may have benefit, but lacks studies in elderly populations. Although tricyclic/tetracyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs) may be effective in the elderly, their side effect and safety profiles are suboptimal and thus are not recommended in late-life. Benzodiazepines and beta blockers should generally be avoided when treating anxiety in the elderly. There is not enough evidence to support the use of antipsychotics or mood stabilizers given their risk of problems in both the long and short term. In addition, antipsychotics have a black box warning for increased mortality in elderly patients with dementia.

Autonomic dysfunction in mild cognitive impairment: evidence from power spectral analysis of heart rate variability in a cross-sectional case-control study

BACKGROUND

Mild cognitive impairment (MCI) is set to become a major health problem with the exponential ageing of the world's population. The association between MCI and autonomic dysfunction, supported by indirect evidence and rich with clinical implications in terms of progression to dementia and increased risk of mortality and falls, has never been specifically demonstrated.

AIM

To conduct a comprehensive assessment of autonomic function in subjects with MCI by means of power spectral analysis (PSA) of heart rate variability (HRV) at rest and during provocative manoeuvres.

METHODS

This cross-sectional study involved 80 older outpatients (aged ≥ 65) consecutively referred to a geriatric unit and diagnosed with MCI or normal cognition (controls) based on neuropsychological testing. PSA was performed on 5-minute electrocardiographic recordings under three conditions--supine rest with free breathing (baseline), supine rest with paced breathing at 12 breaths/minute (parasympathetic stimulation), and active standing (orthosympathetic stimulation)--with particular focus on the changes from baseline to stimulation of indices of sympathovagal balance: normalized low frequency (LFn) and high frequency (HFn) powers and the LF/HF ratio. Blood pressure (BP) was measured at baseline and during standing. Given its exploratory nature in a clinical population the study included subjects on medications with a potential to affect HRV.

RESULTS

There were no significant differences in HRV indices between the two groups at baseline. MCI subjects exhibited smaller physiological changes in all three HRV indices during active standing, consistently with a dysfunction of the orthosympathetic system. Systolic BP after 10 minutes of standing was lower in MCI subjects, suggesting dysautonomia-related orthostatic BP dysregulation.

CONCLUSIONS

Our study is novel in providing evidence of autonomic dysfunction in MCI. This is associated with orthostatic BP dysregulation and the ongoing follow-up of the study population will determine its prognostic relevance as a predictor of adverse health outcomes.

Mind and heart: heart rate variability in major depressive disorder and coronary heart disease - a review and recommendations

OBJECTIVE

There is a reciprocal association between major depressive disorder (MDD) and coronary heart disease (CHD). These conditions are linked by a causal network of mechanisms. This causal network should be quantitatively studied and it is hypothesised that the investigation of vagal function represents a promising starting point. Heart rate variability (HRV) has been used to investigate cardiac vagal control in the context of MDD and CHD. This review aims to examine the relationship of HRV to both MDD and CHD in the context of vagal function and to make recommendations for clinical practice and research.

METHODS

The search terms 'heart rate variability', 'depression' and 'heart disease' were entered into an electronic multiple database search engine. Abstracts were screened for their relevance and articles were individually selected and collated.

RESULTS

Decreased HRV is found in both MDD and CHD. Both diseases are theorized to disrupt autonomic control feedback loops on the heart and are linked to vagal function. Existing theories link vagal function to both mood and emotion as well as cardiac function. However, several factors can potentially confound HRV measures and would thus impact on a complete understanding of vagal mechanisms in the link between MDD and CHD.

CONCLUSIONS

The quantitative investigation of vagal function using HRV represents a reasonable starting point in the study of the relationship between MDD and CHD. Many psychotropic and cardiac medications have effects on HRV, which may have clinical importance. Future studies of HRV in MDD and CHD should consider antidepressant medication, as well as anxiety, as potential confounders.

Treatment of generalized anxiety disorder: a comprehensive review of the literature for psychopharmacologic alternatives to newer antidepressants and benzodiazepines

OBJECTIVE

Generalized anxiety disorder (GAD) is common, chronic, and debilitating. Treatment with benzodiazepines and newer antidepressants is often inadequate. This article reviews the effectiveness of alternative and augmenting medications, such as older antidepressants, antipsychotics, anticonvulsants, and β-blockers.

DATA SOURCES

A search using MEDLINE (1980 to week 4 of May 2010) with the key words generalized anxiety disorder or GAD and therapeutics or treatment was conducted. Articles included adult patients with a GAD diagnosis that established chronicity of illness. These included a small number of studies that used DSM-III criteria but added a chronicity of symptoms and included all studies that used DSM-III-R and DSM-IV criteria. Articles that did not include medications or that exclusively focused on newer antidepressants (selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, bupropion, and mirtazapine), buspirone, benzodiazepines, or herbal or investigational medications were excluded. Review articles and non-English-language articles were also excluded.

RESULTS

Thirty-six studies were reviewed. All of the references were then analyzed, and key portions were extracted. Many studies were open trials. Double-blind, placebo-controlled studies with imipramine, risperidone, olanzapine, hydroxyzine, ondansetron, tiagabine, valproate, and pregabalin had been conducted. Imipramine, hydroxyzine, valproate, and pregabalin were the most effective, although risperidone, olanzapine, ziprasidone, and aripiprazole may also reduce symptoms.

CONCLUSIONS

Several medication strategies can be considered as promising alternatives or augmenting to antidepressant or benzodiazepine therapy in GAD.

Physiological regulation in high-risk infants: A model for assessment and potential intervention

The model presented identifies the importance of neural regulation of autonomic state as an antecedent substrate for emotional, cognitive, and behavioral regulation. It is proposed that individual differences in neural regulation of autonomic state are related to normal and abnormal development. Establishing nervous system regulation of autonomic state is the infant's initial task of self-regulation. Survival for the high-risk infant is based primarily on physiological self-regulation. Although the methods described focus on the high-risk neonate, the model provides insight into normal development and may be generalized to the study of older children and adults with behavioral and psychological problems. Moreover, the model may contribute to assessment and intervention strategics for normal and abnormal development.

Cardiac vagal control in depression: a critical analysis

Rapidly developing research has found abnormal cardiac vagal control (CVC) in several physical and mental health conditions. CVC findings in depression are mixed, and the degree to which CVC is compromised in depression is unclear. A meta-analysis of 13 rigorous cross-sectional studies reveals that a diagnosis of depression exerts a small-to-medium effect size on CVC, and explains only about 2% of the overall variance in CVC. More robust data may emerge from alternative approaches to the depression-CVC relationship, such as the use of CVC to predict the course of the disorder. Despite the vigor of recent work on CVC and depression, overall findings are suggestive rather than conclusive. Methodological desiderata and priorities for future research are discussed, including the need to clarify the etiological significance of CVC.

A meta-analytic review of the efficacy of drug treatment in generalized anxiety disorder

A meta-analytic review of the efficacy of pharmacological treatment in generalized anxiety disorder was conducted. The main substance classes were compared: benzodiazepines and azapirones. The impact of methodological variables was investigated such as sample size and use of a placebo run-in. After a comprehensive literature search to May 2002 (via databases, hand search, secondary sources, internet, contact of researchers, and pharmaceutical companies), the results of 48 studies were integrated. Weighted Hedges g was computed and a random-effects analysis was done. Effect sizes were computed for anxiety, depression, and clinical significance. Sensitivity analyses were conducted. Pharmacotherapy was superior to placebo in all symptom categories. Azapirones and benzodiazepines were equally effective. Compliance (as measured by dropout rate) was higher for benzodiazepines. Only sample size was significantly associated with effect size. Pharmacotherapy, especially benzodiazepines and azapirones, is effective in the short-term treatment of patients with generalized anxiety disorder. There was no superiority of 1 drug class in reducing symptomatology.

Physiological arousal in females with fragile X or Turner syndrome

Physiological arousal was measured in 12- to 22-year-old females with either fragile X, Turner syndrome, or neither disorder to explore potential differences in the manifestation of arousal and anxiety in adolescents and young women. Physiological arousal was measured at baseline and during performance on mental arithmetic, divided attention, and risk-taking tasks. Contrary to prediction, females with fragile X rarely exhibited higher arousal than females in either the Turner syndrome or comparison groups. On the Divided Attention Task, both the fragile X and Turner syndrome groups exhibited higher arousal relative to one another based on different physiological indices. Relative to the comparison group, the fragile X group presented with a heightened state of arousal at baseline, based on mean skin conductance range, which may account for little increase in arousal on the cognitive tasks for females with fragile X. Females with Turner syndrome exhibited higher arousal relative to the comparison group on all cognitive tasks, but not for all physiological measures. Factors potentially associated with heightened arousal in fragile X and Turner syndrome are discussed.

Major depression with ischemic heart disease: effects of paroxetine and nortriptyline on long-term heart rate variability measures

BACKGROUND

Studies have linked depression to sudden death and serious cardiovascular events in patients with preexisting cardiac illness. Recent studies have shown decreased vagal function in cardiac patients with depression and depressed patients without cardiac illness.

METHODS

We compared 20-hour, sleeping, and awake heart period variability measures using spectral analysis, fractal dimension, and symbolic dynamics in two patient groups with major depression and ischemic heart disease (mean age 59-60 years) before and after 6 weeks of paroxetine or nortriptyline treatment.

RESULTS

Spectral measures showed decreases in awake and sleeping total power (TP: 0.0-0.5 Hz), ultra low frequency power (ULF: 0-0.0033 Hz), very low frequency power (VLF: 0.0033-0.04 Hz), and low-frequency power (LF: 0.04-0.15 Hz) for nortriptyline condition and a decrease in high-frequency power (HF: 0.15-0.5 Hz) for the awake condition in patients who received nortriptyline. A measure of nonlinear complexity, WC-100, significantly increased after paroxetine during the awake condition.

CONCLUSIONS

These findings suggest that nortriptyline has stronger vagolytic effects on cardiac autonomic function compared with paroxetine, which is in agreement with previous clinical and preclinical reports. Paroxetine may have some cardio-protective effects, especially in cardiac patients.

Short-term effects of intravenous benzodiazepines on autonomic neurocardiac regulation in humans: a comparison between midazolam, diazepam, and lorazepam

OBJECTIVES

To evaluate the effects of intravenously applied diazepam, lorazepam, and midazolam on autonomic neurocardiac regulation assessed by standardized measurements of heart rate variability.

DESIGN

Prospective, randomized clinical study.

SETTING

University teaching hospital.

PATIENTS

Forty-five patients, who underwent a gastroscopy, were randomly assigned to intravenous premedication with midazolam (5 mg), diazepam (10 mg), or lorazepam (4 mg). Six subjects refused an injection and served as nonpremedicated controls.

INTERVENTIONS

Serial recordings of the 5-min resting heart rate variability were obtained before and 15 and 30 mins after premedication. Seven benzodiazepine-treated patients received intravenous flumazenil (0.5 mg).

MEASUREMENTS AND MAIN RESULTS

The average doses applied were 0.07 mg/kg for midazolam, 0.13 mg/kg for diazepam, and 0.06 mg/kg for lorazepam. Fifteen minutes after intravenous benzodiazepines were administered, we found an increase in resting heart rate and a reduction of vagal tone compared with baseline in all three benzodiazepine-treated subgroups. Multivariate analysis (covariate age) of the changes in heart rate variability indices over the experimental course revealed a significant reduction in absolute high-frequency power with midazolam or diazepam compared with nonpremedicated subjects. Moreover, midazolam-treated subjects showed a significantly larger reduction in relative high-frequency power not only compared with nontreated subjects, but also compared with lorazepam- or diazepam-treated subjects. Vagal tone remained reduced compared with baseline even 30 mins after benzodiazepine application, however, the resting heart rate decreased toward baseline levels. After flumazenil administration, there was a linear correlation between an increase in high-frequency power and a corresponding decrease in resting heart rate.

CONCLUSIONS

Benzodiazepines can influence autonomic neurocardiac regulation in man, probably through their interaction with the gamma-aminobutyric acidA-receptor chloride ion channel complex. The pattern of findings suggests that intravenous midazolam, diazepam, and lorazepam influence human autonomic neurocardiac regulation in a biphasic way. First, they cause a reduction of central vagal tone, and second, they may decrease the cardiac pacemaker directly. Flumazenil completely abolished the autonomic neurocardiac regulation effects of benzodiazepines.

Vagal modulation of responses to mental challenge in posttraumatic stress disorder

BACKGROUND

Studies of the autonomic nervous system in posttraumatic stress syndrome (PTSD) have focused on the sympathetic modulation of arousal and have neglected the parasympathetic contribution. This study addresses the parasympathetic control of heart rate in individuals who have survived traumatic events.

METHODS

Twenty-nine survivors, 14 with current PTSD and 15 without, participated in the study. The groups were comparable with regard to age, type of trauma, time since the latest traumatic event, and lifetime exposure to traumatic events. Electrocardiograms were recorded during rest and an arithmetic task. Heart period, respiratory sinus arrhythmia (RSA), and the amplitude of the Traube-Hering-Mayer wave were quantified.

RESULTS

The groups did not differ on resting measures. During the arithmetic task, the past trauma group showed a significant increase in RSA (p <.007), whereas the PTSD group did not. In the past trauma group only, RSA and heart period were highly correlated (r =.75), thereby suggesting that the response to challenge was under vagal control.

CONCLUSIONS

Trauma survivors who develop PTSD differ from those who do not in the extent to which their heart rate response to challenge is controlled by vagal activity. Responses to challenge in PTSD may be mediated by nonvagal, possibly sympathetic mechanisms.

Anxiety and arousal: physiological changes and their perception

Contrary to self-reports, most patients with chronic anxiety disorders exhibit increased muscle tension but not autonomic hyperarousal when at rest. Under everyday stress they tend to react with less physiological flexibility than normal controls. However, they overreact subjectively and physiologically to stimuli that are anxiety-provoking. Diminished physiological flexibility may be either a constitutional trait in anxious individuals, a partial but inadequate adaptation to prolonged stress or the result of a disregard for stressors that are not related to psychopathology. The effects of diminished physiological flexibility on general health are not known. There is only a weak relationship, and in some instances a desynchrony, between physiological changes and perception of change under stress. The inconsistencies between self-reports of physiological states and physiological recordings can be explained by alterations of body sensations through psychological factors, predominantly expectations and attention to bodily states, that lead to perceptual distortions.

Therapeutic effects of imipramine are counteracted by its metabolite, desipramine, in patients with generalized anxiety disorder

Imipramine has been shown to reduce anxiety in patients with generalized anxiety disorder (GAD). However, some properties of imipramine may diminish or counteract its anxiolytic effects. The authors previously found that the greater the reduction in cardiac vagal control after 6 weeks of imipramine treatment, the smaller the improvement in anxiety-related symptoms. The purpose of this study was to determine whether the authors' previous findings were replicable and to gather information on the plasma levels of imipramine, desipramine (the major metabolite of imipramine), and anticholinergic levels. Fourteen patients with GAD were administered imipramine for 6 weeks. Their scores from self-administered and investigator-administered rating scales were obtained before and after the treatment, and the changes in these scores were contrasted with the changes in cardiac vagal tone, along with the absolute plasma levels of imipramine, desipramine, and anticholinergic activity at the end of week 6. The authors observed a greater improvement in symptoms of anxiety in those who showed the smallest decreases in cardiac vagal tone and in those who showed the smallest increases in desipramine and anticholinergic plasma levels. Moreover, strong relationships were observed between desipramine and anticholinergic levels. These results demonstrate that imipramine not only has therapeutic effects, but it may also have properties that result in physiologic states that counteract its therapeutic effects. Future research should investigate the direct anticholinergic effects of desipramine and determine whether there is a parallel between the anticholinergic effects and the clinical outcome of other pharmacologic treatments, including antidepressants with predominantly norepinephrine or serotonin reuptake inhibitory properties.

Influence of age on the parasympatholytic property of tricyclic antidepressants

Clinical evidence indicates that parasympatholytic effects of tricyclic antidepressants increase with age. The aim of the present study was to determine the possible physiological reason for this phenomenon. Subjects included 23 patients (14 female) with major depression, melancholic type, and 23 age- and sex-matched healthy control subjects. Cardiac vagal tone was measured at rest using both spectral analysis and a time domain beat-to-beat method. Results of the spectral and time domain methods for the estimation of vagal tone used in this study were highly correlated in control subjects as well as in medicated depressed subjects. Both patients and control subjects showed an age-related decline in cardiac vagal tone. Tricyclic antidepressants decreased vagal tone significantly by 25-49% depending on age (20-60 years), although the age difference was not significant. The greater effect of tricyclic antidepressants on parasympathetic activity typically seen in older age groups may reflect the fact that predrug levels of vagal tone are already low in older patients. Measurement of vagal tone prior to drug administration may therefore be of prognostic value for anticholinergic side effects.

Psychic and somatic anxiety: worries, somatic symptoms and physiological changes

Contrary to self-reports, patients with generalized anxiety disorder exhibit increased muscle tension but not autonomic hyperarousal. Under stress they tend to react autonomically in a less flexible manner than normal controls. There is only a weak relationship, and in some instances a desynchrony, between physiological changes and perception of change. The inconsistencies between self-reports of physiological states and physiological recordings can be explained by alterations of body sensations through psychological factors, predominantly expectations of and attention to bodily states, that lead to perceptual distortions.

Noninvasive indices of autonomic regulation after alprazolam and lorazepam: effects on sympathovagal balance

Skin conductance level (SCL) and spectral analysis of variations in heart rate (HR) and blood pressure (BP), in relation to plasma catecholamine concentrations, were used to evaluate autonomic nervous system activity during situations of supine rest within a period of 4 h after oral administration of 1 mg alprazolam and 2 mg lorazepam. Twelve healthy men received in a double-blind, randomized crossover design, either 1 mg alprazolam, or 2 mg lorazepam, or a placebo on different days. ECG, BP, respiration, and SCL were monitored continuously during each session. For HR, systolic and diastolic BP (SBP, DBP) time series, power spectra were calculated per 5 min for three 15-min periods at 30 min, 1 h and 45 min, and 3 h after dosing. Spectral power was assessed for three frequency bands: low (0.02-0.06 Hz), mid (0.07-0.14 Hz), and high (0.15-0.50 Hz). Per time segment, the gain in the mid-frequency band between the systolic BP values and the RR interval times was computed as index of baroreflex sensitivity (BRS). Blood samples for assay of plasma catecholamines were obtained after each 15-min period. Alprazolam reduced DBP during the whole recording period; the effect was accompanied by an initial increase of mid-frequency band fluctuations of BP at 30 min, which subsequently decreased at 1 h 45 min and 3 h after dose administration, in comparison with placebo (suggesting an initial reflectory increase, followed by an attenuation of sympathetic tone). The BP effects were accompanied by a reduction of plasma noradrenaline concentrations. HR showed a time-dependent decrease after alprazolam and an increase in high-frequency band fluctuations of HR and BRS (suggesting a time-dependent increase in cardiac vagal tone). SCL was decreased after alprazolam administration. Lorazepam did not show a time-dependent reduction of HR and had no effect on BP, but increased low-frequency band power of HR and DBP and mildly reduced SCL. Alprazolam and lorazepam had no effect on respiratory frequency. Noninvasive indices of autonomic regulation revealed several small, but significant, time-dependent effects of 1 mg alprazolam on sympathetic and parasympathetic processes, whereas for 2 mg lorazepam, these effects were less clear. The reduction in noninvasive indices of sympathetic tone after alprazolam administration corresponded with the attenuation of plasma noradrenaline concentrations by alprazolam.

Anxiety and cardiovascular reactivity: the basal forebrain cholinergic link

The relations between anxiety states and autonomic functions are considered from the vantage of a model of the neural systems underlying anxiety and autonomic control. An important component of this model is the involvement of the basal forebrain cortical cholinergic system that is seen to play a crucial role in the cognitive aspects of anxiety, and the links between anxiety and autonomic regulation. An additional aspect of the model is the detailing of the routes by which autonomic reactivity and associated visceral afference can modulate more rostral components of the system. The proposed model offers a more comprehensive framework for research on the neurobiology of anxiety and autonomic control.

Increased heart rate in depressed subjects in spite of unchanged autonomic balance?

A clinical study was conducted to examine the effects of depression on cardiac autonomic control. Cardiac autonomic control was measured in 26 nonmedicated patients (19 females) suffering from Major Depression, melancholic type, and in 26 age- and sex-matched normal controls. We measured heart rate and high frequency heart rate variability (respiratory sinus arrhythmia), pulsewave velocity and blood pressure, during 10 min of supine rest under controlled conditions. Using a log transformed time domain measure of respiratory sinus arrhythmia (logRSA), we found an inverse linear dependence between cardiac vagal tone and age in the healthy subjects as well as the depressed patients. logRSA was 0.22+/-0.25 in the patients and 0.25+/-0.16 in the control group. While this difference was not significant (P > 0.1), the deviations from the regression line were significantly (P < 0.0005) greater in the patients (0.21+/-0.12) than in the control group (0.09+/-0.07), indicating a more heterogeneous vagal tone in the depressed patients. Heart rate was also significantly (P < 0.03) greater in the depressed patients (76.6+/-12.4) than in the control group (69.5+/-6.9). No between-group differences were found in pulsewave velocity or systolic blood pressure, but diastolic blood pressure was lower in depressed patients (73.5+/-8.7 vs. 80.8+/-9.1). We discuss the possibility that the increased heart rate seen in the absence of vagal tone changes may not be due to altered vagal or sympathetic tone, as measured in this study. Other factors, including altered autonomous heart rate, may be responsible for the higher heart rate in the depressed group.

Major depression and cardiac autonomic control

We investigated autonomic control of heart rate in patients with major depression, melancholic type. Twenty-three depressed inpatients who were being treated with tricyclic antidepressants and 23 depressed patients who were taking no medications were compared with age- and sex-matched control groups on resting cardiac vagal tone and heart rate. In unmedicated depressed patients, cardiac vagal tone was comparable to that of control subjects, but heart rate was significantly higher. This increase in heart rate may have been due to sympathetic activation caused by anxiety, since the depressed patients were significantly more anxious than the control subjects. Medicated patients exhibited diminished cardiac vagal tone and higher heart rate than unmedicated patients and controls. This was probably due to the anticholinergic effects of the antidepressants. Our findings suggest that cardiac vagal tone is not lower than normal in patients with depression, melancholic type.

A novel tool to quantify physical activities: ambulatory accelerometry in psychopharmacology

Accelerometry by means of body-mounted piezoresistive sensors was evaluated as a new method to quantify physical activities (body posture and physical and locomotor activity) in relation to the sedative and cardiovascular effects of benzodiazepines, in an ambulatory study. In a double-blind, randomized, crossover study, 12 healthy men received either an oral dose of 2 mg lorazepam, 0.5 mg alprazolam, 1 mg alprazolam, or a placebo on 4 different days. By means of a portable digital recorder, each day 4 hours of continuous measurements of accelerometer signals and heart rate were performed in a living room in the hospital. Changes in subjective sleepiness were assessed at the beginning, halfway, and at the end of the recording period. A separate validation study of the ambulatory environment was performed in three subjects, in which computer classification of activities based on accelerometry was compared with visual evaluation of simultaneously recorded videotapes. In our validation study, comparison of the computer classification with visual analysis based on videotapes revealed an overall agreement for spontaneous and standardized activities of 88% and 96%, respectively. In our pharmacological study, the subjects spent more time in the lying position (p < 0.01) and less time in the sitting position (p < 0.01) after benzodiazepine administration; the effects were strongest for lorazepam. Motility during static activities was reduced (p < 0.025), with motility after lorazepam administration being lowest. Both lorazepam and alprazolam (0.5 and 1 mg) increased subjective sleepiness (p < 0.01). On average , lorazepam induced an overall increase in mean heart rate of about 6%, whereas alprazolam reduced mean heart rate by 2% versus placebo (p < 0.01); the effects were not dependent on posture. The validation study showed that accelerometry forms a reliable method to quantify aspects of normal daily activities. Our pharmacological study revealed that quantification of body postures, physical activity, and motility by means of ambulatory accelerometry proves to be an objective and promising tool to evaluate the psychological and cardiovascular effects of (psycho) pharmaca in relation to the postural and mobility activities of normal daily life.

Lorazepam reduces cardiac vagal modulation in normal subjects

Benzodiazepines are frequently administered postmyocardial infarction, but their effect on heart period variability (HPV), a prognostic index of sudden arrhythmogenic death, is unclear. In fact, in both humans and animals, previous studies utilizing acute intravenous doses yielded mixed results. We hypothesized that lorazepam (LZ), by potentiating gamma-aminobutyric acid-A-ergic inhibition of preganglionic vagal neurons projecting to the heart, would reduce cardiac vagal modulation. We therefore tested LZ's effect on HPV over 24 hours of normal physiologic activity in human volunteers in the presence of steady-state LZ. A double-blind, randomized, placebo-controlled study was conducted. Seven healthy subjects received LZ or placebo for 1 week, 1 week taper, then crossed over. Electrocardiogram recordings measured HPV after the administration of drug and placebo for 24 hours. LZ increased mean heart rate by 8% (p < 0.002), decreased the standard deviation of R-R intervals by 9% (p < 0.05), decreased the percent differences between adjacent normal R-R intervals > 50 msec by 30% (p < 0.002), decreased the root-mean-square successive difference by 17% (p < 0.02), and decreased the natural logarithm of high-frequency power by 6% (p < 0.03). The significant heart rate increase and HPV decreases demonstrate vagolytic effects of LZ in healthy subjects during 24 hours of normal physiologic activity.

Cardiovascular variability in major depressive disorder and effects of imipramine or mirtazapine (Org 3770)

Spectral analysis of fluctuations in heart rate (HR) and blood pressure (BP) was applied to assess sympathetic and parasympathetic cardiovascular control mechanisms in patients with unipolar affective disorder before and after treatment with imipramine (IMI) or mirtazapine (MIR). In a double-blind randomized study, 10 patients received treatment with IMI and 10 patients received treatment with MIR. Cardiovascular parameters were studied before and after 4 weeks of treatment: HR and BP (Finapres) were recorded continuously during supine rest (SR) and orthostatic challenge (OC; 60-degrees head-up tilting). During SR and OC, power spectra were calculated for HR and systolic BP. Spectral density was assessed for three frequency bands: low (0.02-0.06 Hz), mid (0.07-0.14 Hz), and high (0.15-0.50 Hz). Before treatment, the depressed patients (N = 20) differed from age-matched controls (N = 20) only in their response to OC: the depressed patients showed more suppression of HR variability (both mid- and high-frequency band fluctuations), indicating stronger vagal inhibition, and a reduced increase of BP variability (mid-frequency band fluctuations), indicating reduced sympathetic activation. After 4 weeks of treatment, patients treated with either antidepressant drug showed significant changes of HR (increase) and HR variability (decrease) during SR and OC; the suppression of mid- and high-frequency fluctuations of HR was larger for IMI than for MIR. The increase in HR and decrease in HR variability may be attributed to the anticholinergic properties of IMI (strong) and MIR (weak), resulting in cardiac vagal inhibition. Whereas MIR had no effect on BP or BP variability, IMI specifically reduced mid-frequency band fluctuations of BP as the result of a suppression of central sympathetic activity. Our data confirm and extend previous observations on the presence of autonomic dysfunctions in unmedicated depressed patients: spectral analysis of HR and BP fluctuations suggested that both parasympathetic and sympathetic mechanisms are involved, specifically during OC. The preexisting autonomic cardiovascular dysfunctions were not normalized by antidepressant drugs. In fact, some of the components of the cardiovascular autonomic dysfunction were further aggravated, depending on the pharmacologic profile of the drug under investigation.

Effects of desipramine on autonomic control of the heart

OBJECTIVE

To assess the effects of desipramine (DMI) on autonomic control of the heart.

METHODS

Blood pressure, RR interval (the time between successive heart beats), and RR interval variability, a noninvasive measure of autonomic control of the heart, were assessed in 13 subjects younger than 30 years old.

RESULTS

DMI treatment was associated with an increase in blood pressure, a decrease in RR interval, and a decline in low and high frequency RR interval variability.

CONCLUSIONS

These preliminary data suggest that, in young people, DMI treatment produces a substantial decrease in parasympathetic input to the heart and an increase in the ratio of sympathetic to parasympathetic input, changes that in certain circumstances have been associated with an increased risk of arrhythmia. In exploring the cardiac effects of the tricyclic antidepressants (TCAs) in young people, the impact of TCAs on autonomic input to the heart should be examined.