Computational Evaluation of a Turbulence-like Electrical Activity Hypothesis in Atrial Fibrillation: Substrate Remodeling, Critical Wavelength Transition, and Multi-wavelet Maintenance

BACKGROUND: Atrial fibrillation (AF) remains difficult to explain using a single focal driver or rotor-centered mechanism across disease stages. We tested whether progressive atrial substrate remodeling can drive a critical transition toward turbulence-like, decentralized multi wavelet electrical activity. METHODS: We constructed a controlled two-dimensional atrial reaction-diffusion model with six graded substrate-remodeling stages. We evaluated effective wavelength, theoretical wavelet capacity, AF inducibility, vulnerable-window dynamics, spatial randomness, temporal memory, spectral dispersion, nonlinear indices, virtual ablation response and ERP-prolongation reverse mechanistic testing. RESULTS: Progressive remodeling shortened effective wavelength from 12.0 to 2.4 cm and increased theoretical wavelet capacity from 0.69 to 17.36. Inducibility rose sigmoidally as wavelength shortened, with a model-derived transition near lambda50=4.5 cm. Advanced substrates showed increased wavebreak, spatial randomness, short-memory dynamics, broad spectral dispersion, positive nonlinear indices and resistance to random local ablation. Culprit atrial premature beats within the vulnerable window efficiently triggered AF, whereas counter pacing at 20 to 35 ms reduced inducibility from 52% to 11% in stage 2. CONCLUSIONS: In this controlled model, AF initiation and maintenance were linked to substrate-dependent wavelength, wavelet capacity and vulnerable-window triggering. The model-derived transition provides a testable framework for future high-density mapping, patient30 specific modeling and device-based studies. Key Words atrial fibrillation; turbulence-like electrical activity; substrate remodeling; critical wavelength; multi-wavelet re-entry; vulnerable window; culprit premature atrial beat; counter pacing