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Bundle branch block on alternate beats: by what mechanism?
Vincenzo Carbone1, Michele Adolfo Tedesco
1Medical Surgical Department of Cardio-Thoracic Sciences, Second University of Naples, Naples, Italy. enzo.carbone@tiscalinet.it
Journal of Electrocardiology
|April 16, 2002
Summary
Right bundle branch block alternans, a conduction issue, resolved with faster heart rates and returned with slower rates. Bradycardia-dependent block best explains this alternating pattern in intraventricular conduction.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Conduction System
Background:
- Right bundle branch block (RBBB) can present with complex patterns, including alternans, where the block alternates between beats.
- Understanding the electrophysiological mechanisms underlying RBBB alternans is crucial for diagnosing and managing cardiac conduction abnormalities.
Observation:
- A case study observed RBBB alternans during regular sinus rhythm that resolved with hyperventilation-induced tachycardia.
- The conduction disturbance reappeared upon carotid sinus massage, leading to a slight decrease in sinus rate.
Findings:
- Analysis excluded phase-3 2:1 bidirectional block and phase-3 antegrade block with subsequent "supernormal" conduction as mechanisms.
- The study favored a phase-4 antegrade block with transseptal retrograde concealed invasion.
- Bradycardia-dependent right bundle branch block was identified as the primary mechanism explaining the observed alternans pattern.
Implications:
- This finding highlights the importance of heart rate in the manifestation of certain conduction blocks.
- Understanding bradycardia-dependent RBBB is essential for interpreting ECG findings in patients with intermittent conduction disturbances.
- The study contributes to the understanding of the electrogenesis of bundle branch block alternans, aiding in clinical diagnosis.