Autonomic Imbalance, Endothelial Dysfunction, Peripheral Artery Disease
Conditions
Brief summary
Peripheral arterial disease (PAD) constitutes a major public health burden. The incidence of PAD increases with age and is associated with other comorbid cardiovascular disorders. Atherosclerosis which underlies PAD is associated with increased arterial stiffness and an enhanced inflammatory state as evidenced by increased levels of pro-inflammatory cytokines and markers. One the earliest signs of cardiovascular disease is endothelial dysfunction which is characterized by a decreased vasodilatory capacity of the vascular endothelium and this lesion predates the development of clinical atherosclerosis. Endothelial dysfunction has been shown to be widely prevalent in PAD. It is postulated that endothelial dysfunction is due to enhanced sympathetic drive, diminished parasympathetic drive, chronic inflammatory state all of which leads to reduced nitric oxide synthase activity in the vascular endothelium with subsequent loss of vasodilatory capacity. Studies have shown endothelial dysfunction to be reversible with pharmaco-therapeutic interventions, though these interventions are associated with their own adverse effects. Stimulation of Vagal nerve increases the parasympathetic activity while suppressing sympathetic drive, decreases inflammation and enhancing nitric oxide synthase activity. Recent experimental and clinical data suggest that low-level tragus nerve stimulation (by stimulating the auricular branch of the vagus nerve located at the tragus of the external ear) may produce the same desired neuromodulator effect compared to vagus nerve stimulation. It is however unknown if Transcutaneous Vagal Stimulation (TVS) would lead to improved endothelial function as measured by flow mediated dilatation (FMD) and laser speckle contrast imaging(LSCI), a non-invasive method of measuring endothelial function or decrease in arterial stiffness as measured by Pulse Wave Analysis (PWA), in patients with PAD. The objective of this study is to determine the impact of TVS on endothelial dysfunction as measured by FMD & LSCI and arterial stiffness. Study population will include patients with established diagnosis of PAD. After performing baseline FMD, LSCI and PWA patients will be randomized to TVS and sham stimulation with cross over. The patient randomized to TVS stimulation will obtain stimulation for 1 hour followed by measurement of FMD,LSCI and PWA. There will be a washout period of at least 24 hours with patient crossing over to the other arms thus serving as their self-control.
Interventions
Sponsors
University of Oklahoma
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
TREATMENT
Masking
TRIPLE (Subject, Caregiver, Outcomes Assessor)
Masking description
Blinding will be done so the investigator performing the FMD, LSCI and PWA testing will be blinded to the allocation of TVS
Intervention model description
This is a pilot study.
Eligibility
Sex/Gender
ALL
Age
18 Years to 85 Years
Healthy volunteers
No
Inclusion criteria
1. peripheral arterial disease (PAD) - patients with an ankle-brachial index of \<0.9 2. symptoms of intermittent claudication, rest pain, or minor tissue loss (Rutherford category I-V)
Exclusion criteria
1. patients with acute limb ischemia 2. Patients with overt congestive heart failure / recent acute myocardial infarction (\< 3 months) 3. Premenopausal women and post-menopausal women on hormone supplements. 4. chronic inflammatory disease (systemic lupus erythematosus, rheumatoid arthritis, and Crohn's disease), or receiving therapy with steroids, cyclosporine, methotrexate or immunocompromised patients. 5. unilateral or bilateral vagotomy 6. Patients with bilateral upper extremity amputation 7. pregnant patients 8. prisoners 9. end-stage renal disease. 10. End-stage liver disease. 11. patients with BMI\>34 12. Patients with upper extremity arterial disease 13. history of recurrent vasovagal syncope, Sick sinus syndrome, 2nd- or 3rd-degree atrioventricular block (AV) block, prolonged first degree AV block. 14. Refusal to sign a consent form. 15. Significant hypotension from autonomic dysfunction 16. Patients with pacemakers who have significant interaction with TVNS during testing
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Flow mediated vasodilatation | Change from baseline to post stimulation(within 10 minutes of stimulation) with TVS/Sham stimulation | Flow mediated vasodilatation will be tested. A change in the maximal diameter of the brachial artery(in mm) will be assessed immediately(within 10 minutes) after TVNS/sham stimulation. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Endothelial function in microcirculation | Change from baseline to post stimulation(within 20-30 minutes of stimulation) with TVS/Sham stimulation | LSCI based calculation of perfusion unit before and after TVS/Sham stimulation |
| Pulse wave analysis | Change from baseline to post stimulation(within 15-20 minutes) with TVS/Sham stimulation. | Arterial elasticity. Augmentation pressure (AP) will be calculated which is expressed as a percentage of the aortic pulse pressure (PP) which is the difference of systolic and diastolic BP(mm Hg). |
Countries
United States
Contacts
PRINCIPAL_INVESTIGATORTarun Dasari, MD, MPH
University of Oklahoma
Outcome results
None listed