Evidence for multiple mechanisms in human ventricular fibrillation

Area of Science:

• Cardiac Electrophysiology
• Arrhythmia Mechanisms
• Medical Imaging and Signal Processing

Background:

• The precise mechanisms driving ventricular fibrillation (VF) in humans remain incompletely understood.
• Existing experimental models propose either a stable 'mother rotor' or multiple chaotic wavelets as the underlying cause of VF.
• This study aimed to investigate the electrical activity patterns of the human ventricular epicardium during early VF.

Purpose of the Study:

• To map epicardial electrical activity across the entire human ventricle during early VF.
• To determine the relative contributions of the 'mother rotor' and multiple wavelet hypotheses in sustaining human VF.
• To elucidate the dynamic interplay between different electrophysiological mechanisms during VF.

Main Methods:

• Induced VF in 10 cardiac surgery patients via burst pacing.
• Recorded epicardial electrical activity using a 256-electrode sock (UnEmap system) at 1 kHz.
• Utilized signal interpolation, Fast Fourier Transform (FFT) for dominant frequencies (DFs), and Hilbert transform for phase singularity and wavefront analysis.

Main Results:

• Early human VF involved large, coherent wavefronts interspersed with disorganized wavelet activity.
• Dominant frequencies (DFs) showed an initial intercept of 5.11 Hz and increased over time.
• Epicardial reentry was consistently observed, often with few phase singularities, sometimes interacting with multiple wavelets or driven by a single reentrant wave.

Conclusions:

• The findings support the coexistence of both 'mother rotor' and multiple wavelet mechanisms in human VF.
• These mechanisms are not mutually exclusive and can operate concurrently in the human heart.
• Human VF exhibits complex electrophysiological dynamics involving both organized and disorganized electrical activity.