Study of How Different Heart Rates Affect Stroke Volume and Cardiac Output Using Pacemakers in Adults Aged 18 to 70

What this Trial Is About

Researchers are studying how different heart rates affect stroke volume and cardiac output in patients with vasovagal syncope who have permanent pacemakers. This study aims to clarify how increasing heart rate impacts the hearts ability to fill with blood and pump effectively, both when lying down and when upright. The investigation addresses a gap in understanding the relationship between heart rate and cardiac function in this group. The study involves pacing the heart at various rates ranging from 50 to 130 beats per minute while monitoring stroke volume and cardiac output using non-invasive methods. After completing pacing runs while lying down, participants rest for 10 minutes before being tilted upright at an angle greater than 70 degrees for about 10 minutes, followed by additional pacing sessions. Blood pressure is measured and the equipment calibrated between pacing runs. Participants will undergo assessments that include continuous monitoring of stroke volume and cardiac output during different pacing rates and positions. The primary outcome is the change in cardiac output during atrial pacing at different rates while lying down. Secondary outcomes include changes in cardiac output and stroke volume during various pacing modes and body positions. The entire study procedure occurs within one day, and safety is ensured by using non-invasive techniques and secure positioning during upright testing.

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