Effect of ventricular function on the exercise hemodynamics of variable rate pacing

Area of Science:

• Cardiology
• Exercise Physiology
• Biomedical Engineering

Background:

• Ventricular function significantly impacts cardiovascular response to exercise.
• Optimizing pacemaker settings is crucial for improving exercise capacity in patients with cardiac conditions.

Purpose of the Study:

• To evaluate the impact of single rate (VVI) versus variable rate (VVIR) pacing on exercise hemodynamics.
• To determine if baseline left ventricular function influences the hemodynamic response to different pacing modes during exercise.

Main Methods:

• 16 patients underwent randomized, double-blind exercise tests comparing VVI and VVIR pacing modes.
• Ejection fraction and cardiac index were assessed using echocardiography at rest and peak exercise.
• Patients were stratified into two groups based on baseline ejection fraction (<40% and >=40%).

Main Results:

• Exercise duration was significantly longer in VVIR mode (502s) compared to VVI mode (449s).
• Heart rate increased by 9% in VVI and 35% in VVIR mode during exercise (p<0.005).
• Cardiac index increased by 49% in VVI and 83% in VVIR mode, significantly influenced by pacing mode and exercise intensity, not baseline ejection fraction.

Conclusions:

• VVIR pacing enhances exercise duration, heart rate, and cardiac index compared to VVI pacing.
• These improvements are observed regardless of the degree of baseline left ventricular dysfunction in selected patients.
• Variable rate pacing offers a hemodynamic advantage during exercise in patients with pacemakers.