Vasovagal syncope Circulatory System
Conditions
Interventions
Volunteers will be asked to undergo a “tilt test” to assess cardiovascular reflex control and orthostatic tolerance (measured as time to presyncope, or near fainting, in minutes). We and others have p
Sponsors
Simon Fraser University
Eligibility
Sex/Gender
All
Inclusion criteria
Inclusion criteria: 1. Healthy, English-speaking men and women aged 16-50 years 2. In order to reduce the likelihood of transmission of COVID-19, participants are only eligible to participate in the study if they have received full immunisation against COVID-19 according to current Health Canada guidelines. Accordingly, participants will be asked to provide evidence of their vaccination status in order to take part in the study.
Exclusion criteria
Exclusion criteria: 1. Women will be excluded if they are pregnant, or think they might be 2. Participants who self-identify as having cardiovascular or neurological disease will be excluded from the study, as these factors may influence the outcome of the study 3. Individuals who suffer from recurrent fainting episodes (=2 episodes of syncope in the prior 6 months) will be excluded 4. Contraindications to EMLA anesthetic cream: previous diagnoses of liver disease, methemoglobinemia or GP6D deficiency; known allergy to lidocaine or prilocaine; breastfeeding; pregnancy. Out of an abundance of caution and given the known potential interactions between certain medications and EMLA, participants taking any prescription medications will be excluded (with the exception of hormonal contraceptives).
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| Orthostatic tolerance in minutes, determined using a head-upright tilt test with combined lower body negative pressure. Orthostatic tolerance is a measure of fainting susceptibility and represents the time it takes from tilt test initiation, to the time at which a significant drop in blood pressure is observed, consistent with a pre-syncopal (near-fainting) response. Measured on three separate days after each of the three different exposures. | — |
Secondary
| Measure | Time frame |
|---|---|
| 1. Sodium levels (a marker of salt intake and hydration) measured using a urine sample before the tilt test Measures of cardiovascular reflex control recorded continuously and non-invasively at baseline and throughout the tilt test: 2. Heart rate measured using a standard three-lead ECG 3. Beat-to-beat blood pressure will be determined using the Finometer blood pressure monitoring device. This consists of a small Velcro cuff placed around the middle finger that pulses gently against the digital arteries and records and displays blood pressure with every heartbeat. 4. Any influence of possible hyperventilation and the associated decreases in carbon dioxide on cerebral blood flow, evaluated using end tidal gases sampled using a nasal cannula 5. Cerebral blood flow determined in the middle cerebral artery using Doppler ultrasound. An ultrasound probe will be positioned on the skin overlying the temple and held in place with a headband. Participants can move their heads freely when wearing the ultrasound probe. 6. Blood flow in the brachial artery, measured with ultrasound. The arm will be placed on a support with a probe positioned over a little ultrasound gel near the elbow. | — |
Countries
Canada
Outcome results
None listed