The effect of ventricular activation sequence on cardiac performance during pacing

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Physiology

Background:

• Normal ventricular activation is crucial for efficient cardiac performance.
• Understanding optimal pacing strategies is essential for managing cardiac conditions.

Purpose of the Study:

• To evaluate the impact of normal ventricular activation patterns on cardiac function.
• To compare the hemodynamic effects of atrial pacing and different ventricular pacing sites (septal vs. apical) with varying atrioventricular (AV) delays.

Main Methods:

• Mongrel dogs underwent radiofrequency-induced complete heart block.
• Atrial pacing was compared to AV synchronous pacing at various AV delays.
• Proximal septal AV synchronous pacing was compared to apical AV synchronous pacing.
• Hemodynamic parameters including dP/dt, cardiac output, and pressures were assessed.

Main Results:

• Atrial pacing demonstrated superior hemodynamic performance (positive and negative dP/dt, cardiac output) compared to AV synchronous pacing across all AV delays.
• Proximal septal pacing resulted in higher positive and negative dP/dt than apical pacing.
• Left ventricular activation time was significantly shorter with proximal septal pacing (88 ms) versus apical pacing (115 ms).

Conclusions:

• Atrial and proximal septal pacing enhance cardiac function and shorten ventricular activation time.
• These benefits are independent of the atrioventricular interval.
• Optimizing ventricular activation patterns through pacing improves cardiac performance.