Vasovagal SyncopePacing_SVNCT03446326
Assessment of Stroke Volume and Cardiac Output in Response to Varying Heart Rates
A study testing Pacing in people with Vasovagal Syncope, run by University of Calgary at 1 site in Canada.
Trial summary
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… Read more about this study
- Who is it for?
- Ages 18 to 70 years
- Conditions the study is for
- Vasovagal Syncope
- What is being tested?
- Pacing
- Type of treatment
- Medical device
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 25 participants
- Where
- 1 siteCanada
- Study dates
- 1 Jan 2018to 1 Jan 2028
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 70 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Age 18-70 years (inclusive)
- Implanted permanent pacemaker or implanted defibrillator capable of atrial and ventricular pacing
- LV ejection fraction >50%
Who cannot join
- Unable or unwilling to provide informed consent
- Clinical need for a cardiac resynchronization device
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Canada1 site, 1 recruiting
- Recruiting
University of Calgary
Calgary, Alberta, T2N 4Z6
Satish R Raj, MD, MSCI, 403-210-6152, autonomic.research@ucalgary.ca
Robert S Sheldon, MD, PhD, 403-220-8191, autonomic.research@ucalgary.ca
About this study
Official title: Assessment of Stroke Volume and Cardiac Output in Response to Varying Heart Rates and Body Position - a Pacemaker Based Study
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.
Read the detailed description
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.
- Conditions
- Vasovagal Syncope
- Being tested
- Pacing
- Keywords
- pacemaker, stroke volume, cardiac output, heart rate
- Medical subject headings
- Syncope, Vasovagal
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
PacingDevice
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%)
| Study group | Role | What they receive |
|---|---|---|
| Stroke volume and cardiac output | Experimental | 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. Receives: Device: Pacing |
What is being measured
The primary outcome is the main question the study is designed to answer.
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)
Measured: 1 day
Secondary outcomes (7)
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
Measured: 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
Measured: 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
Measured: 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
Measured: 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
Measured: 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
Measured: 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
Measured: 1 day
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted26 Feb 2018
- Study start1 Jan 2018
- Primary completion1 Jan 2027 (estimated)
- Study completion1 Jan 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Vasovagal SyncopeStudies of the same condition, open and under way.
- More trials run by University of CalgaryThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 25 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of Calgary
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Satish R Raj, MD MSCI, Principal investigator, University of Calgary
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT03446326
- Sponsor's protocol ID
- REB15-2887
- Acronym
- Pacing_SV
- Status last verified
- Apr 2026
- First submitted
- 31 Jan 2018
- Last updated
- 5 May 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- Yes
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 5 May 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Assessment of Stroke Volume and Cardiac Output in Response to Varying Heart Rates and Body Position - a Pacemaker Based Study
- ClinicalTrials.gov ID
- NCT03446326
- Acronym / sponsor ID
- Pacing_SV / REB15-2887
- Conditions
- Vasovagal Syncope
- Keywords
- pacemaker, stroke volume, cardiac output, heart rate
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 25 participants (estimated)
- Lead sponsor
- University of CalgaryUniversity, hospital or other
- Study start
- 1 Jan 2018 (actual)
- Primary completion
- 1 Jan 2027 (estimated)
- Study completion
- 1 Jan 2028 (estimated)
- First posted
- 26 Feb 2018 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Detailed description
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.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Stroke volume and cardiac output | Experimental | Device: PacingPacing 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. |
Who may qualify
- Ages
- 18 to 70 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- Age 18-70 years (inclusive)
- Implanted permanent pacemaker or implanted defibrillator capable of atrial and ventricular pacing
- LV ejection fraction >50%
Key exclusion criteria (2 listed)
- Unable or unwilling to provide informed consent
- Clinical need for a cardiac resynchronization device
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| PacingAssess 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%) | Device | Stroke volume and cardiac output |
Primary outcome
Change in cardiac output while atrial pacing at lower and higher rates while supine
Time frame: 1 day
Change in cardiac output (CO) when atrial pacing at 80 bpm \& 120 bpm while supine. CO = HR x Stroke volume (SV)
7 secondary outcomes
Change in cardiac output at lower and higher ventricular (VVI) paced rates while supine
Time frame: 1 day
Change of cardiac output at lower and higher atrial (AAI) paced rates while supine versus while upright
Time frame: 1 day
Change of cardiac output at lower and higher ventricular (VVI) paced rates while supine versus while upright
Time frame: 1 day
Change in stroke volume at lower and higher 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
Time frame: 1 day
Change of stroke volume at lower and higher atrial (AAI) paced rates while supine versus while upright
Time frame: 1 day
Change of stroke volume at lower and higher ventricular (VVI) paced rates while supine versus while upright
Time frame: 1 day
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 5 May 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Satish R Raj, MD MSCI principal investigator
University of Calgary
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Pacing in people with Vasovagal Syncope, run by University of Calgary at 1 site in Canada.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 2 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 5 May 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Canada. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Satish R Raj, MD MSCI (4032106152, satish.raj@ucalgary.ca), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in cardiac output while atrial pacing at lower and higher rates while supine (time frame: 1 day). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 5 May 2026.