Vagus Nerve Stimulation: Integration of Behavior and Cardiac Modulation

Not Applicable

Completed

Conditions: Major Depressive Disorder

Interventions: Device: exhalatory-gated transcutaneous vagus nerve stimulation (e-RAVANS)
Device: Inhalatory-gated transcutaneous vagus nerve stimulation (i-RAVANS)

Registration Number: NCT04467164

Lead Sponsor: Massachusetts General Hospital

Brief Summary: This study characterized the impact of respiratory-gated transcutaneous vagus nerve stimulation (tVNS) on the modulation of the stress response circuitry, vagal tone and depressed mood in patients with major depressive disorder (MDD). Twenty premenopausal women with recurrent MDD in an active episode were recruited into a single-blind cross-over study that included two functional MRI visits within a one week period with simultaneous mood and physiological assessments. Randomization to exhalatory- or inhalatory-gated tVNS was performed to control for order effects. The study hypothesis was that exhalatory-gated tVNS would have a significantly greater impact on the regulation of brain activity in stress response circuitry, vagal tone and depressed mood in MDD patients compared to inhalation-gated tVNS. This is not a clinical trial aimed to test a medical device, but a basic experimental study oriented to understand the effects of vagal afference modulation on brain and cardiovagal physiological response to stress in major depression.

Detailed Description: Major depressive disorder (MDD) has been associated with alterations of the stress response circuitry, including the hypothalamus, amygdala, hippocampus, anterior cingulate cortex, ventromedial, dorsolateral and orbital prefrontal cortices. Many of these regions are morphologically and functionally sexually dimorphic and associated with vulnerability for sex differences in MDD. A major role for the stress response circuitry is to assess potentially stressful stimuli and respond with a neuroendocrine signal that coordinates homeostatic responses throughout the body. Neuroimaging studies have suggested that alterations in this circuitry are implicated in mood dysregulation, increased activation of the hypothalamic-pituitary-adrenal (HPA) axis, and imbalance between the sympathetic and parasympathetic nervous system in depressed persons. A better understanding of the mechanisms underlying alterations in physiological response to stress in major depression may contribute to the development of novel interventions that regulate this system with a significant impact on the improvement of clinical and physiological alterations of MDD.

It has been previously suggested that modulation of vagus nerve activity may have a significant effect on the modulation of the brain circuitry involved in the regulation of mood and stress response. Recently, a non-invasive approach for modulation of vagus nerve activity, transcutaneous auricular vagus nerve stimulation (tVNS), which targets the auricular branch of the vagus nerve (ABVN) has been proposed. Moreover, previous studies have shown that vagal afference is highly regulated by respiration and that modulation of vagus nerve activity may be optimized by gating ABVN stimulation to the exhalatory phase of the respiratory cycle. Thus, this study proposed to characterize the impact of respiratory-gated tVNS on the modulation of the stress response circuitry, vagal tone and depressed mood in patients with recurrent major depression (MDD). This is not a clinical trial aimed to test a medical device, but a basic experimental study oriented to understand the effects of vagal afference modulation on brain and cardiovagal physiological response to stress in major depression.

Twenty premenopausal women with recurrent MDD in an active episode were recruited into a single-blind cross-over study that included two functional MRI visits, within a one week period, with simultaneous mood and physiological assessments. Randomization to exhalatory- or inhalatory-gated tVNS was performed to control for order effects. Subjects were exposed to a mild visual stress challenge that preceded and followed 30 minutes of exhalatory- or inhalatory-gated tVNS. The study hypothesis was that exhalatory-gated tVNS would have a significantly greater impact on the regulation of brain activity in stress response circuitry, vagal tone and depressed mood in MDD patients compared to inhalation-gated tVNS

Recruitment & Eligibility

Status: COMPLETED

Sex: Female

Target Recruitment: 20

Inclusion Criteria

Recurrent MDD diagnosis (≥ 2 episodes) with a current active depressive episode.

Exclusion Criteria

History of Axis I psychiatric diagnosis other than MDD or anxiety disorder - e.g., substance use disorder, psychotic disorder, or bipolar disorder.
Current Suicidal Ideation with intent and/or plan or history of suicide attempt within the last year
Use of psychotropic medications within four weeks prior to study with the exception of Selective Serotonin Reuptake Inhibitors (SSRIs) and Selective Norepinephrine Reuptake Inhibitors (SNRIs) class of antidepressant medication only
Use of Tricyclic antidepressants (TCAs), Monoamine oxidase inhibitors (MAOIs), and Atypical agents
History of cardiovascular disease
History of neuroleptic use
Past history of substance abuse or dependence within the past 12 months (excludes nicotine)
Bleeding disorder or use of anticoagulants.
Pregnancy
Metallic implants or devices contraindicating magnetic resonance imaging.
Use of beta blockers

Study & Design

Study Type: INTERVENTIONAL

Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Exhalatory-gated tVNS	exhalatory-gated transcutaneous vagus nerve stimulation (e-RAVANS)	exhalatory-gated tVNS on the left auricle
Inhalatory-gated tVNS	Inhalatory-gated transcutaneous vagus nerve stimulation (i-RAVANS)	inhalatory-gated tVNS on the left auricle

Primary Outcome Measures

Name	Time	Method
Brain Activity Changes (Average Differences in Beta Weights From Significantly Activated Regions: Post-stimulation Minus Pre-stimulation) Evaluated Using Functional Magnetic Resonance Imaging.	1 hour	A functional magnetic resonance imaging (fMRI) analysis was used to evaluate changes in brain activity \[blood oxygenation level-dependent (BOLD) signal\] in response to a visual stress challenge (post- and pre-stimulation). For this analysis a General Lineal Model analsysis with the statistical parametrical software (SPM) was used to model the change in BOLD signals during exposure to negative vs neutral images of the stress tasks. A voxel-wise height threshold of p \< 0.001, and a cluster correction with FWE p-value\<0.05 was used to identify brain areas with significant activation in response to the task. Mean beta weights within each significant cluster were extracted for each participant, and average differences in beta weights (Post minus Pre stimulation) were estimated for each group. A positive difference indicates increased activation of a particular brain region in response to the stimulation, whereas a negative difference indicates a reduction in brain activity.

Secondary Outcome Measures

Name	Time	Method
Change in Depressive Symptoms Assessed by the Beck Depression Inventory (1 Hour Post Intervention Minus Baseline)	2 hours	Changes from baseline to post-stimulation in the total score of the Beck Depression Inventory (BDI) compared between exhalatory and inhalatory-gated tVNS. (Beck depression inventory minimum score= 0, maximum score= 63; higher total scores indicate more severe depressive symptoms). A positive difference at post-stimulation compared to baseline indicates an increase in depressive symptoms, whereas a negative difference indicates a reduction in depressive symptomatology.
Changes in Cardiac Autonomic Function (Percent Change in Normalized High-frequency Power of Heart Rate Variability (HFn-HRV): Post-stimulation Versus Pre-stimulation)	1 hour	Cardiac pulsatility data was collected during exposure to visual stress tasks pre- and post-stimulation and were used to estimate inter-beat intervals. A point process algorithm was then used to analyze the inter-beat intervals and evaluate heart rate variability (HRV) by separating its dynamics in the classic spectral components within the high-frequency (HF) and low-frequency (LF) ranges. Differences in normalized HF \[HFn= (HF/(LF + HF))\] were estimated during exposure to negative images in the fMRI stress task as a metric of parasympathetic cardiac regulation. Percent change in HFn-HRV values (Post vs Pre stimulation) were calculated for each intervention group. A positive percent change value indicates an increase in cardiovagal activity, whereas a negative change indicates a reduction in cardiovagal activity.