NCT03446326

Assessment of Stroke Volume and Cardiac Output in Response to Varying Heart Rates

Assessment of Stroke Volume and Cardiac Output in Response to Varying Heart Rates and Body Position - a Pacemaker Based Study

• Status: Recruiting
• Phase: N/A
• Study type: Interventional
• Enrollment: 25 (estimated)
• Sponsor: University of Calgary · Academic / Other
• Sex: All
• Age: 18 Years – 70 Years
• Healthy volunteers: Not accepted

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 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.

Conditions

• Vasovagal Syncope

Interventions

Type	Name	Description
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%)

Timeline

• Start date: 2018-01-01
• Primary completion: 2027-01-01
• Completion: 2028-01-01
• First posted: 2018-02-26
• Last updated: 2024-05-17

Locations

1 site across 1 country: Canada

Regulatory

• FDA-regulated device study