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Scroll wave dynamics in a three-dimensional cardiac tissue model: roles of restitution, thickness, and fiber rotation
1Department of Medicine (Cardiology), University of California, Los Angeles 90095, USA. zqu@ucla.edu
Insights
Action potential duration restitution drives scroll wave breakup, a key mechanism in cardiac arrhythmias like ventricular fibrillation. Fiber rotation also promotes wave break by maintaining scroll wave twist and curvature.
Area of Science:
- Cardiovascular Physiology
- Computational Biology
- Cardiac Electrophysiology
Background:
- Ventricular fibrillation (VF) is a life-threatening arrhythmia caused by chaotic electrical activity in the heart.
- Scroll wave (vortex) dynamics are a leading hypothesis for the initiation and maintenance of VF.
- Understanding scroll wave breakup is crucial for developing anti-arrhythmic strategies.
Purpose of the Study:
- To investigate the factors influencing scroll wave breakup in a 3D cardiac tissue model.
- To elucidate the roles of action potential duration (APD) restitution, tissue thickness, filament twist, and fiber rotation in scroll wave instability.
- To identify the primary determinants of scroll wave breakup relevant to cardiac fibrillation.
Main Methods:
- Simulated scroll wave behavior in a 3D cardiac tissue model.
- Utilized the Luo-Rudy (LR1) phase I action potential model for simulations.
- Systematically varied parameters including APD restitution, tissue thickness, filament twist, and fiber rotation.
Main Results:
- APD restitution was identified as the predominant factor governing scroll wave behavior and breakup.
- Instabilities arising from APD restitution were the primary drivers of scroll wave breakup.
- Fiber rotation was found to promote scroll breakup by maintaining filament twist and inducing wave curvature, which impairs conduction.
- A minimum tissue thickness was necessary for scroll breakup when fiber rotation was present, but thickness-induced instability was not observed in the LR1 model.
Conclusions:
- APD restitution is the critical determinant of scroll wave breakup in this cardiac model.
- Fiber rotation significantly contributes to scroll wave breakup by influencing wave dynamics and conduction.
- These findings advance our understanding of the mechanisms underlying ventricular fibrillation and potential therapeutic targets.
Abstract:
Scroll wave (vortex) breakup is hypothesized to underlie ventricular fibrillation, the leading cause of sudden cardiac death. We simulated scroll wave behaviors in a three-dimensional cardiac tissue model, using phase I of the Luo-Rudy (LR1) action potential model. The effects of action potential duration (APD) restitution, tissue thickness, filament twist, and fiber rotation were studied. We found that APD restitution is the major determinant of scroll wave behavior and that instabilities arising from APD restitution are the main determinants of scroll wave breakup in this cardiac model. We did not see a "thickness-induced instability" in the LR1 model, but a minimum thickness is required for scroll breakup in the presence of fiber rotation. The major effect of fiber rotation is to maintain twist in a scroll wave, promoting filament bending and thus scroll breakup. In addition, fiber rotation induces curvature in the scroll wave, which weakens conduction and further facilitates wave break.