Variation in activation time during bipolar vs extended bipolar left ventricular pacing

Area of Science:

• Cardiology
• Biomedical Engineering
• Electrophysiology

Background:

• Cardiac resynchronization therapy (CRT) often uses quadripolar leads for pacing.
• True bipolar pacing (BP) is linked to reduced mortality, possibly due to enhanced electrical activation.
• Extended bipole (EBP) pacing is an alternative configuration using quadripolar electrodes and a right ventricular coil.

Purpose of the Study:

• To compare electrical activation patterns between true bipolar (BP) and extended bipole (EBP) left ventricular (LV) pacing during CRT.
• To investigate if BP pacing leads to more favorable LV electrical activation compared to EBP pacing.

Main Methods:

• Electrocardiographic imaging studies were performed on patients undergoing CRT.
• Electrical activation data were recorded while temporary LV pacing vectors (BP and EBP) were programmed.
• Left ventricular total activation time (LVtat) was analyzed.

Main Results:

• No significant differences were found in total electrical activation times or dispersion between BP and EBP LV pacing configurations.
• Analysis dichotomized by etiology (ischemic vs. dilated cardiomyopathy) also showed no difference in activation times.
• LVtat measurements were similar for both pacing methods across different patient groups.

Conclusions:

• True bipolar pacing does not appear to result in more favorable electrical activation of the left ventricle compared to EBP pacing.
• The observed mortality benefits of BP pacing may be due to mechanisms other than improved electrical activation or resynchronization.
• Further investigation into alternative mechanisms underlying the benefits of bipolar pacing in CRT is warranted.