Endocardial Activation Drives Activation Patterns During Long-Duration Ventricular Fibrillation and Defibrillation.

Area of Science:

• Cardiovascular Physiology
• Electrophysiology
• Medical Device Technology

Background:

• Understanding ventricular fibrillation (VF) mechanisms is crucial for improving defibrillation techniques.
• Distinct activity patterns (chaotic, regular, synchronized) exist in VF, persisting in long-duration VF (LDVF).
• Hypothesized endocardial activity drives LDVF patterns and defibrillation shocks alter them.

Purpose of the Study:

• Investigate the role of endocardial activity in driving VF activation patterns.
• Determine if defibrillation shocks affect these patterns.
• Clarify mechanisms of VF termination and maintenance.

Main Methods:

• Utilized a 64-electrode basket catheter on the left ventricle endocardium and 54 plunge needles in 6 dogs.
• Induced VF electrically, recording endocardial activation during short-duration and LDVF.
• Delivered escalating defibrillation shocks until VF termination, classifying activation patterns (chaotic, regular, synchronized).

Main Results:

• Chaotic patterns dominated early VF; regular patterns emerged as VF progressed.
• Synchronized patterns appeared occasionally in late VF.
• Failed shocks converted chaotic/regular to synchronized patterns in LDVF, but not short-duration VF.

Conclusions:

• Endocardial activity drives regular and synchronized activation patterns in LDVF.
• These patterns are maintained by rapid endocardial activation that blocks transmurally.
• Defibrillation shock failure can induce synchronized patterns, potentially hindering VF termination.