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QRS alternans with 2:1 atrioventricular conduction block: what is the mechanism?

Takumi Yamada1, Paul B Tabereaux, H Thomas McElderry

  • 1Division of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, AL 35294-0019, USA. takumi-y@fb4.sonet.ne.jp

Annals of Noninvasive Electrocardiology : the Official Journal of the International Society for Holter and Noninvasive Electrocardiology, Inc
|August 21, 2008
PubMed

Insights

This case study highlights QRS alternans in a patient with bradycardia, suggesting coexisting bundle branch blocks and a high risk of complete atrioventricular block, necessitating pacemaker implantation.

Area of Science:

  • Cardiology
  • Electrophysiology
  • Medical Diagnostics

Background:

  • Symptomatic bradycardia requires prompt diagnosis and management.
  • Electrocardiogram (ECG) interpretation is crucial for identifying cardiac conduction abnormalities.

Observation:

  • An 81-year-old woman presented with symptomatic bradycardia.
  • Initial ECG showed QRS alternans, narrow QRS, left bundle branch block, and 2:1 atrioventricular (AV) block.

Findings:

  • The patient progressed to complete AV block, requiring pacemaker implantation.
  • A proposed mechanism involves differential conduction through both bundle branches (4:1 left, 2:1 right).
  • ECG findings of QRS alternans with narrow QRS, bundle branch block, and 2:1 AV block indicate coexisting blocks and high complete AV block risk.

Implications:

  • This ECG pattern serves as a critical indicator for impending complete heart block.
  • Early recognition can guide timely intervention, such as pacemaker insertion.
  • Understanding differential bundle branch conduction aids in diagnosing complex arrhythmias.

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