Human Ventricular Fibrillation

Abstract

A major controversy in cardiac electrophysiology is whether ventricular fibrillation (VF) is maintained by wandering wavelets or mother rotors. On the basis of a computer model of atrial fibrillation by Moe1 developed in 1962, fibrillation was hypothesized to be maintained by multiple small, wandering wavelets, in which the activation pattern is constantly changing. According to the wandering wavelet hypothesis, fibrillation is maintained by constantly changing reentrant circuits formed by some of the wandering wavelets. Because this random reentry can occur anywhere within the cardiac muscle, this hypothesis suggests that all parts of the ventricular myocardium are equally important for the maintenance of VF. Article p 536 The mother rotor hypothesis was put forward for the maintenance of atrial fibrillation first by Lewis2 and later by Gurvich.3 Recently, this hypothesis has been applied to VF by Jalife’s group.4 This group reported that in isolated guinea pig hearts and in isolated right ventricular slabs of sheep, a long-lived, stationary, stable reentrant circuit that they called a “mother rotor” was present.5,6 The mother rotor gave rise to daughter wavefronts that propagated into the remainder of the myocardium. As opposed to the mother rotor, these daughter wavefronts did not have regular, repeating activation sequences. Instead, activation of the daughter wavefronts was less organized, with changing activation sequences, conduction block, and fractionation. It was these unstable daughter wavefronts that gave rise to the disorganized pattern in the ECG. The region containing the mother rotor had a shorter refractory period than the remainder of the myocardium. Jalife’s group postulated that the reason activation was less organized in the regions outside of the mother rotor was that the longer refractory periods in these regions did not allow them to keep up with the mother rotor, whose cycle length was shorter than their …