Counterpressure Maneuvers: Movements that can aid in delaying or preventing syncope by recruiting skeletal muscle pumping (via compression of major veins by contracting muscle to eject blood through cardiovascular circuit) and increased sympathetic drive (via sustaining an isometric muscle contraction). In this trial, we will be evaluating two clinically recommended isometric maneuvers (crouching, and leg crossing with muscle tensing) and two novel dynamic maneuvers that comprise discrete movement that the investigators have identified in prior work (exaggerated anterior-posterior postural sway, rhythmic gluteal clenching).
Baseline Stand: Participants will stand quietly for 5-minutes on a force platform to allow the investigators to assess their typical response to orthostasis.
Study summary
The investigators are interested in whether discrete counterpressure maneuvers, or muscle movements in the lower body, will boost blood pressure and cardiovascular control in children who faint. We will record cardiovascular responses to maneuvers of exaggerated sway, leg crossing, crouching, and gluteal muscle tensing in children who faint (N=20), as well as their height, weight, muscularity, and pubertal (Tanner) stage. Autonomic cardiovascular control will be measured using a Valsalva manoeuvre (expiration against a closed airway for 20 seconds) and a supine-stand test. The primary outcomes are noninvasive measures of cardiovascular responses to the maneuvers (blood pressure, cerebral blood flow, and stroke volume (volume of blood pumped per heartbeat). Comparisons will be made across levels of sex, diagnosis, Tanner stage, muscularity, height, and degree of autonomic control.
Eligibility
Sex
ALL
Min age
6 Years
Max age
18 Years
Healthy volunteers
No
Inclusion Criteria:
We are looking for English speaking pediatric patients aged 6-18 years with a diagnosis of recurrent fainting (at least two episodes of fainting with loss of consciousness or near loss of consciousness in the last year) of a vasovagal origin or associated with the postural orthostatic tachycardia syndrome (POTS) (as determined by a paediatric cardiologist) to take part in this study.
Exclusion Criteria:
Those with a diagnosis of recurrent fainting accompanied by any of the following will not be eligible to take part:
Known history of:
* Suspected or confirmed cardiac arrhythmia (e.g., Wolff-Parkinson-White, Long QT)
* Traumatic head injury
* New presentation of a seizure disorder OR epilepsy recurrence
* Overdose or intoxication
* Structural heart disease
* Cardiovascular disease including hypertension, diabetes, or renal disease
* Hypoglycemia
* Physical and/or psychological disability that impact their ability to complete the tests
Female participants of childbearing age will be excluded if they are pregnant, or think they might be. Participants who are taking any cardiovascular acting medications, including treatment for cardiovascular disease, or medications for orthostatic syncope (e.g. fludrocortisone, slow-release sodium chloride, β-blockers, midodrine) will be excluded from the study.
In order to reduce the likelihood of transmission of COVID-19, participants will only be 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.
Primary outcome measure(s)
Relationship between postural movement and stroke volume — Final minute of maneuver performance We will correlate these two parameters using both time and frequency domain approaches. We will compare this between the five movement conditions using a one-way repeated measures ANOVA.
This page summarises publicly available registry data for informational purposes — not medical advice. Eligibility is determined by each study team; patients should discuss participation with their clinician.
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