Spatiotemporal evolution of ventricular fibrillation

Abstract

Sudden cardiac death is the leading cause of death in the industrialized world, with the majority of such tragedies being due to ventricular fibrillation. Ventricular fibrillation is a frenzied and irregular disturbance of the heart rhythm that quickly renders the heart incapable of sustaining life. Rotors, electrophysiological structures that emit rotating spiral waves, occur in several systems that all share with the heart the functional properties of excitability and refractoriness. These re-entrant waves, seen in numerical solutions of simplified models of cardiac tissue, may occur during ventricular tachycardias. It has been difficult to detect such forms of re-entry in fibrillating mammalian ventricles. Here we show that, in isolated perfused dog hearts, high spatial and temporal resolution mapping of optical transmembrane potentials can easily detect transiently erupting rotors during the early phase of ventricular fibrillation. This activity is characterized by a relatively high spatiotemporal cross-correlation. During this early fibrillatory interval, frequent wavefront collisions and wavebreak generation are also dominant features. Interestingly, this spatiotemporal pattern undergoes an evolution to a less highly spatially correlated mechanism that lacks the epicardial manifestations of rotors despite continued myocardial perfusion.

Construction and validation of anisotropic and orthotropic ventricular geometries for quantitative predictive cardiac electrophysiology

“…This results in a stationary heart with a geometry similar to end-diastole. Optical imaging using such dyes has allowed the quantitative study of the organization and the development of cardiac arrhythmias in isolated hearts [4,8]. Voltage-sensitive dyes can be introduced through coronary flow in perfused tissue preparations or by superfusion in smaller tissue samples.…”

“…Experimental studies are generally restricted to mapping electrical activity on the ventricular surfaces [4,8], or to multiple plunge electrodes within the heart [9 -11]. Major advances have been achieved through the simultaneous mapping in vitro of endocardial and epicardial activity in slabs of ventricular tissue [12], mid-myocardial measurements from exposed transmural surfaces [13], or using transillumination [14,15], optrodes [16] or dual excitation wavelength epi-fluoresence [17], and the panoramic mapping of activity over the surface of the entire heart [18,19].…”

The effect of ischemia on ventricular fibrillation as measured by fractal dimension and frequency measures

“…The Hurst exponent increases over time and approaches 0.5, which is characteristic of a random signal. This increase in the random nature of VF over time is supported by studies of VF mechanism in which "rotors" are seen to break down into disorganized wave fronts [24,25].…”

Stabilization of inhomogeneous patterns in a diffusion–reaction system under structural and parametric uncertainties

“…In this way, nervous signals are transmitted in the form of periodic flat pulses (fronts) travelling along neural axons and tissues (Hodgkin and Huxley, 1952). Normal heart activity is also sustained by regular electrochemical fronts which being produced by the heart's natural peacemaker spread throughout the cardiac tissue and induce contraction (Fenton and Karma, 1998;Witkowski et al, 1998).…”

“…Heart arrhythmia (Witkowski et al, 1998) is one of such disorders produced by a regular front being broken into a wandering spiral. In the last instance and after a chain breaking process, the spiral waves would transform into a disorganized set of multiple spirals continually created and destroyed, being this pattern characteristic of fibrillation (Keener, 2004).…”