Increased wave break during ventricular fibrillation in the epicardial border zone of hearts with healed myocardial...

Area of Science:

• Cardiovascular Physiology
• Cardiac Electrophysiology
• Myocardial Infarction Research

Background:

• The mechanism of wave break during ventricular fibrillation (VF) in the epicardial border zone (EBZ) of hearts with chronic myocardial infarction remains unclear.
• Understanding this phenomenon is crucial for developing targeted therapies for VF in post-infarction patients.

Purpose of the Study:

• To investigate the role of the EBZ in wave dynamics during VF in a canine model of healed myocardial infarction.
• To determine if the action potential duration (APD) restitution hypothesis explains wave break in the EBZ.

Main Methods:

• Induction of VF and sequential mapping of the EBZ and surrounding regions in dogs with induced myocardial infarction and control dogs.
• High-resolution electrode mapping to analyze wavefronts, reentry patterns, and approximate entropy.
• Assessment of dynamic APD restitution curves and Connexin43 expression in the EBZ.

Main Results:

• The EBZ exhibited significantly higher wavefront density and incidence of spontaneous wave breaks compared to other mapped regions.
• Reentry in the EBZ was characterized by a smaller core perimeter, slower rotation, and a reduced or absent excitable gap.
• The APD restitution curve in the EBZ showed longer diastolic intervals with a slope greater than 1, and significantly reduced Connexin43 staining.

Conclusions:

• A selective increase in wave break and altered reentry dynamics occur in the EBZ of hearts with healed myocardial infarction.
• These findings are consistent with the action potential duration restitution hypothesis as a mechanism for increased wave break in the EBZ during VF.