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Related Experiment Videos

Activation sequences following failed atrial defibrillation.

Xiangsheng Zheng1, Jian Huang, Gregory P Walcott

  • 1Division of Cardiovascular Diseases, Department of Medicine, University of Alabama at Birmingham, 35294, USA.

Heart Rhythm
|April 27, 2005
PubMed
Summary
This summary is machine-generated.

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This study reveals that earliest postshock activation in atrial fibrillation (AF) occurs at sites with short preshock cycle lengths. Successful defibrillation and most failed attempts show focal activation, while some failed shocks indicate reentry due to conduction block.

Area of Science:

  • Cardiovascular Electrophysiology
  • Atrial Fibrillation Mechanisms
  • Defibrillation Science

Background:

  • Limited understanding of atrial fibrillation (AF) mechanisms compared to ventricular defibrillation.
  • Need to elucidate AF recurrence post-shock and defibrillation success factors.

Purpose of the Study:

  • Investigate earliest postshock activations in atrial fibrillation (AF).
  • Understand AF relapse mechanisms after failed defibrillation shocks.
  • Compare postshock activation patterns between failed and successful shocks.

Main Methods:

  • Induced sustained AF in sheep using methylcholine and electrical stimulation.
  • Delivered biphasic subthreshold shocks using three electrode configurations (RA-CS, Sequential, V-triad).

Related Experiment Videos

  • Performed global atrial mapping with 504 electrodes (3-4 mm spacing) and detailed mapping (1.5 mm spacing) on the right atrial appendage.

    • Main Results:

    • Earliest postshock activation location varied by electrode configuration, often originating from the left atrium.
    • Sites of earliest activation exhibited shorter preshock AF cycle lengths.
    • Successful shocks and most failed shocks (50/72) showed focal activation patterns with non-fragmented electrograms.
    • A subset of failed shocks (22/72) displayed nonfocal activation with fragmented electrograms, suggesting conduction block and potential reentry.

    Conclusions:

    • Electrode configuration impacts earliest postshock activation site.
    • Earliest postshock activation is associated with short preshock AF cycle lengths.
    • Focal activation patterns characterize successful defibrillation and most failed attempts, while fragmented electrograms in failed shocks suggest reentry mechanisms.