Pseudo bundle branch block produced by premature impulses arising in the bundle branches

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Arrhythmias

Background:

• Sick sinus node syndrome (SNS) is a complex cardiac arrhythmia.
• Bundle branch blocks (BBB) affect cardiac conduction pathways.
• Concealed conduction, where premature impulses do not manifest on surface ECG, poses diagnostic challenges.

Observation:

• Two patients with SNS presented with an uncharacterized arrhythmia.
• Surface ECGs did not reveal concealed conduction.
• Intracardiac electrograms were vital for localizing the impulse origin.

Findings:

• Pseudo bundle branch block (pseudo-BBB) was identified, arising from concealed premature impulses in the bundle branches.
• Patient 1 exhibited pseudo-BBB and pseudo-atrioventricular block due to concealed left bundle branch extrasystoles.
• Patient 2 showed a right bundle branch block pattern possibly caused by pseudo-BBB from right bundle branch extrasystoles.

Implications:

• This research introduces pseudo-BBB as a new arrhythmia entity.
• Understanding concealed conduction is critical for diagnosing complex arrhythmias in SNS patients.
• Further investigation may clarify the role of mechanical factors in these arrhythmias.