Vasovagal Syncope | Mechanisms of Vasovagal Syncope
Vasovagal Syncope research study
What is the primary objective of this study?
Vasovagal Syncope (simple postural faint) is the most common cause of acute loss of consciousness. Postural tachycardia syndrome(POTS) is the most common chronic form of postural lightheadedness. Together they afflict many Americans, mostly young women, who are prevented from gainful employ or school attendance. The underlying mechanism is not known. Our past work suggests that a simple molecule, nitric oxide, acts to subvert normal blood flow controls causing blood to pool in the gut when standing. Our proposal will show the mechanism behind this problem and will indicate effective medical treatments. Patients will be compared to healthy control subjects.
Who is eligible to participate?
Inclusion Criteria: 1. POTS patients referred for day to day orthostatic intolerance with greater than 3 symptoms for greater than 3 months and will have the diagnosis of symptomatic postural tachycardia made during a screening tilt table test : - dizziness - nausea and vomiting - palpitations - fatigue - headache - exercise intolerance - blurred vision - abnormal sweating heat. 2. Vasovagal Syncope patients will have at least 3 episodes of fainting episodes in the past year. 3. Healthy control subjects Cases will be between the ages of 14 and 29 years old Cases will have normal physical examination, and normal electrocardiographic and echocardiographic evaluations. Only those free from heart disease, and from systemic illness will be eligible to participate. This excludes patients with illnesses and disease states known to be associated with endothelial cell dysfunction such as diabetes, renal disease, congestive heart failure, systemic hypertension, acute and chronic inflammatory diseases, neoplasm, immune mediated disease, trauma, morbid obesity and peripheral vascular disease. At the time of testing all patients and control subjects must refrain from vasoactive drugs for two weeks. Please check with us about any medication that you are taking. Exclusion Criteria: - Cardiovascular causes of syncope - An active medical condition that may explain the diagnosis - A previous medical condition with undocumented resolution that may explain the diagnosis - Past or present major psychiatric disorder - Substance abuse within 2 years before onset of symptoms.
Which medical condition, disease, disorder, syndrome, illness, or injury is researched?
Postural Tachycardia Syndrome
Interventions can include giving participants drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available or noninvasive approaches such as surveys, education, and interviews.
Drug:PhenylephrinePhenylephrine dose-response comprises infusion of 0.5, 1, 2, 3, 4 micrograms/kg/min for 10 min at each dose. If bloods pressure increases by 30% or if heart rate decreases below 40 beats per minute we will stop infusion.
Drug:L-Ng-monomethyl Arginine (L-NMMA)Systemic L-NMMA is infused as a 500μg/kg/min loading dose for 15 min followed by a 50μg/kg/min maintenance dose for the remainder of the experiment.
Research studies and clinical trials typically have two or more research arms. An arm is a group of people who receive the same treatment in the study.
Phenylephrine and L-Ng-monomethyl Arginine (L-NMMA)
Active, not recruiting
Start Date: February 2013
Completed Date: July 2019
Phase: Early Phase 1
Primary Outcome: Heart rate and blood pressure in response to Lower Body Negative Pressure(LBNP)
Secondary Outcome: Adrenergic neurotransmission as measured by Muscle Sympathetic Nerve Activity(MSNA), doppler ultrasound blood flow, venous Norepinephrine in response to Phenylephrine infusion
Study sponsors, principal investigator, and references
Principal Investigator: Julian M. Stewart, M.D., Ph.D.
Lead Sponsor: New York Medical College