Epicardial ECG mapping of human ventricular fibrillation

Although the mechanisms of ventricular fibrillation (VF) have been studied extensively in animal hearts, relatively few studies have investigated VF in the human heart. The aim of this study was to record epicardial activity during early human VF and analyse the electrical signals in order to characterise the complexity of activity and to estimate the number of reentrant sources driving the VF. In 10 patients undergoing routine cardiac surgery, VF was induced by burst pacing and a 20-40 s episode of fibrillatory activity was recorded from a dense array of unipolar electrodes spanning the entire epicardium. Dominant frequencies were computed using the fast Fourier transform. Activation times were computed at the minimum negative slopes of the electrograms. Phase singularities and activation wavefronts were identified and quantified. We found that early human VF was typically sustained by a small number of re-entrant sources that were associated with large and coherent wavefronts. However, at times we also observed a large number of small wavefronts. Our results suggest that multiple electrophysiological mechanisms sustain VF in the human heart.