Dissociation and delayed conduction in the canine right bundle branch.

Area of Science:

• Cardiovascular Electrophysiology
• Cardiac Anatomy and Physiology

Background:

• The right bundle branch (RBB) is critical for cardiac impulse conduction.
• Understanding RBB electrophysiology under stress is vital for diagnosing arrhythmias.

Purpose of the Study:

• To investigate the electrophysiological properties of the RBB during antegrade and retrograde activation.
• To examine the effects of stress (premature stimulation, mechanical pressure) on RBB conduction.
• To determine if RBB conduction abnormalities can simulate re-entrant arrhythmias.

Main Methods:

• Bipolar electrograms recorded from multiple sites on the canine RBB using a multielectrode patch.
• Antegrade conduction assessed during sinus rhythm and atrial pacing.
• Retrograde activation induced by ventricular pacing.
• Conduction delays studied using premature stimulation and mechanical RBB compression.

Main Results:

• Right bundle conduction velocities ranged from 1.4 to 3.3 m/sec (mean 2.0 m/sec) for antegrade and 1.8 to 2.7 m/sec (mean 2.1 m/sec) for retrograde conduction.
• Conduction delays occurred in localized RBB segments, with recovery of normal conduction distally.
• Delays were associated with fragmented electrograms and delayed activation waves.

Conclusions:

• Stress-induced longitudinal dissociation in the RBB can create delayed activation waves.
• These phenomena may mimic the electrophysiological patterns of re-entrant arrhythmias.
• Findings highlight potential mechanisms for arrhythmias originating from RBB conduction disturbances.