An interventional study of Pacing in Vasovagal Syncope, sponsored by University of Calgary. Recruiting at 1 site in Canada. Open to participants aged 18 Years to 70 Years. Per ClinicalTrials.gov, last updated 2026-05-05.
Sponsored by University of Calgary · Not applicable, Interventional, and Treatment
The investigators will seek to determine the effects of different heart rates on both stroke volume and cardiac output using non-invasive hemodynamic assessments. In order to safely manipulate the HR, the investigators will study patients with permanent pacemakers in whom heart rate manipulation can be done in a safe and non-invasive manner.
Permanent pacemakers have sometimes been used to treat patients with recurrent vasovagal syncope. This is because patients with vasovagal syncope often experience bradycardia at the time of their syncope. Unfortunately, pacemakers are often ineffective in preventing syncope.
Classical cardiovascular hemodynamics would suggest that increasing the heart rate (HR; via pacemaker) should increase the cardiac output (CO). This is because:
CO = HR x Stroke volume (SV).
The assumption is that the SV is fixed during manipulation of the HR. However, this might not be the case. As the number of beats per minute (HR) increases, the cardiac cycle length (R-R interval [RRI]) shortens, as a function of simple math. This means that the time in cardiac systole shortens, and the time in cardiac diastole shortens. Since cardiac diastole is when the heart fills up with blood, faster HR can be associated with decreased cardiac filling times. This, in turn, could compromise the SV. However, there is a paucity of data as to what happens to SV and CO at different HR. Further, it is possible that these effects will be different when a person is lying down supine versus when a patient is upright (when stroke volume will be lower).
The investigators will seek to determine the effects of different HR on both SV \& CO. In order to safely manipulate the HR, they will study patients with permanent pacemakers in whom HR manipulation can be done in a safe and non-invasive manner.
88 studies on the registry are indexed under Syncope, Vasovagal; 28 are open to participants now.
This study's planned enrollment of 25 is below the median of 59 across 58 interventional studies indexed under Syncope, Vasovagal.
Browse Syncope, Vasovagal studies →University of Calgary is the lead sponsor of 703 studies on the registry; 196 are open to participants now.
Of its 10 completed or terminated interventional studies of FDA-regulated products, 2 (20%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
LVEF (left ventricular ejection fraction)
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Pacing runs will occur at the following rates: * 50 beats per minute (bpm) * 60 bpm * 70 bpm * 80 bpm * 90 bpm * 100 bpm * 110 bpm * 120 bpm * 130 bpm The finger blood pressure cuff will be calibrated between pacing runs. Following the final pacing run while supine, the patient will be given 10 minutes to rest prior to the upright portion of the study. They will then be strapped into the table (so they will not fall) and then they will be tilted up to \>70 degrees (almost standing up). They will stand for \~10 minutes prior to commencing the next pacing trains.
Device: Pacing
Assess the non-invasively determined stroke volume and cardiac output response at different paced heart rates in patients with a cardiac pacemaker or implanted defibrillator with preserved ejection fractions (LVEF≥50%)
Change in cardiac output while atrial pacing at lower and higher rates while supine
Change in cardiac output (CO) when atrial pacing at 80 bpm \& 120 bpm while supine. CO = HR x Stroke volume (SV)
Time frame: 1 day
Change in cardiac output at lower and higher ventricular (VVI) paced rates while supine
Change in Cardiac output at ventricular (VVI) paced rates when it is lower (50-70 bpm) and higher (130 bpm) while supine
Time frame: 1 day
Change of cardiac output at lower and higher atrial (AAI) paced rates while supine versus while upright
Change of cardiac output at lower and higher atrial (AAI) paced rates while supine versus while upright at different paced rates
Time frame: 1 day
Change of cardiac output at lower and higher ventricular (VVI) paced rates while supine versus while upright
Change of cardiac output at lower and higher ventricular (VVI) paced rates while supine versus while upright at different paced rates
Time frame: 1 day
Change in stroke volume at lower and higher atrial paced rates while tilted up
Change in stroke volume at lower (50-70 bpm) vs. higher (130 bpm) atrial paced rates while tilted up
Time frame: 1 day
Change in stroke volume at lower and higher ventricular (VVI) paced rates while tilted up
Change in stroke volume at ventricular (VVI) paced rates when it is lower (50-70 bpm) and higher (130 bpm) while tilted up
Time frame: 1 day
Change of stroke volume at lower and higher atrial (AAI) paced rates while supine versus while upright
Change of stroke volume at lower and higher atrial (AAI) paced rates while supine versus while upright at different paced rates
Time frame: 1 day
Change of stroke volume at lower and higher ventricular (VVI) paced rates while supine versus while upright
Change of stroke volume at lower and higher ventricular (VVI) paced rates while supine versus while upright at different paced rates
Time frame: 1 day
Plan to share: No
No publications or documents are linked to this record.
Started Jan 2018 (actual). Primary completion is estimated for Jan 2027, 108 months after the start.
Of 29 interventional studies with no phase under Syncope, Vasovagal, half reached primary completion within 39 months of starting (the median), counting those still running; a quarter within 15. This study's planned 108 months is above that.
How these figures are worked out, and which studies are left out of them.
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