ECG and Pacing Criteria for Differentiating Conduction System Pacing from Myocardial Pacing

Area of Science:

• Cardiology
• Electrophysiology
• Medical Instrumentation

Background:

• Accurate His-Purkinje system (HPS) pacing requires distinguishing HPS capture from myocardial capture.
• Non-selective (ns) capture involves the HPS and adjacent myocardium, while myocardial-only capture affects only the myocardium.

Purpose of the Study:

• To review methods for differentiating HPS capture from myocardial-only capture during His-Purkinje system pacing.
• To elucidate the electrocardiographic and electrophysiological bases for this differentiation.

Main Methods:

• Analysis of QRS complex morphology during HPS vs. myocardial pacing.
• Exploitation of differences in conduction velocity, refractoriness, and capture thresholds.
• Application of dynamic pacing maneuvers: differential output, programmed stimulation, and burst pacing.

Main Results:

• HPS capture leads to faster, more homogenous left ventricular (LV) depolarization compared to right ventricular septal (RVS) myocardial capture.
• LV depolarization during HPS capture is simultaneous with QRS onset, mimicking native activation.
• Distinct QRS morphologies arise from these depolarization differences, enabling electrocardiographic differentiation.

Conclusions:

• Electrocardiographic criteria and dynamic pacing maneuvers are effective for diagnosing HPS capture.
• Understanding tissue properties (conduction, refractoriness, thresholds) is key to accurate HPS capture assessment.