Evidence for Multiple Mechanisms in Human Ventricular Fibrillation

Abstract

Background-The mechanisms that sustain ventricular fibrillation (VF) in the human heart remain unclear. Experimental models have demonstrated either a periodic source (mother rotor) or multiple wavelets as the mechanism underlying VF. The aim of this study was to map electrical activity from the entire ventricular epicardium of human hearts to establish the relative roles of these mechanisms in sustaining early human VF. Methods and Results-In 10 patients undergoing cardiac surgery, VF was induced by burst pacing, and 20 to 40 seconds of epicardial activity was sampled (1 kHz) with a sock containing 256 unipolar contact electrodes connected to a UnEmap system. Signals were interpolated from the electrode sites to a fine regular grid (100ϫ100 points), and dominant frequencies (DFs) were calculated with a fast Fourier transform with a moving 4096-ms window (10-ms increments). Epicardial phase was calculated at each grid point with the Hilbert transform, and phase singularities and activation wavefronts were identified at 10-ms intervals. Early human VF was sustained by large coherent wavefronts punctuated by periods of disorganized wavelet behavior. The initial fitted DF intercept was 5.11Ϯ0.25 (meanϮSE) Hz (PϽ0.0001), and DF increased at a rate of 0.018Ϯ0.005 Hz/s (PϽ0.01) during VF, whereas combinations of homogeneous, heterogeneous, static, and mobile DF domains were observed for each of the patients. Epicardial reentry was present in all fibrillating hearts, typically with low numbers of phase singularities. In some cases, persistent phase singularities interacted with multiple complex wavelets; in other cases, VF was driven at times by a single reentrant wave that swept the entire epicardium for several cycles. Conclusions-Our data support both the mother rotor and multiple wavelet mechanisms of VF, which do not appear to be mutually exclusive in the human heart. (Circulation. 2006;114:536-542.)

Control of electrical turbulence by periodic excitation of cardiac tissue

“…First direct experimental observations of such states were reported almost 20 years ago 6,7 . Recent experimental and simulations studies 8,9 show a complex picture with states dominated by one or a few mother rotors as well as multiple wave dynamics characterized by a mean number of 10 vortices on the surface of, e. g., a human heart. The fluctuations in vortex number resemble a Poissonian statistics.…”

The Photodiode Array: A Critical Cornerstone in Cardiac Optical Mapping

“…Others believe that fibrillation is maintained by the constant creation and annihilation of wavelets which occur due to functional and anatomical heterogeneities (Choi et al, 2002;Lee et al, 1996;Moe, 1962;Rogers et al, 1999;Valderrábano et al, 2002). More recently, some groups have concluded that fibrillatory activity may be driven by both mechanisms, depending on specific conditions in the heart Liu et al, 2004;Nash et al, 2006;Wu et al, 2002). Mutual information techniques have been used to examine the relationship between V m and Ca i .…”

Pacemakers in a Reaction-Diffusion Mechanics System

“…Problems in the electrical system of the heart may result in cardiac arrhythmias, e.g. rapid activation and spatial desynchronization of mechanical contractions in the heart, (26,30) which cause the mechanical pump function of the heart to malfunction. In the US alone, more than 450,000 people die suddenly each year as a result of cardiac arrhythmias.…”