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(Circulation Research. 2002;91:339.)
© 2002 American Heart Association, Inc.

Integrative Physiology

Life Span of Ventricular Fibrillation Frequencies

Bum-Rak Choi, Wonchul Nho, Tong Liu, Guy Salama

From the Department of Cell Biology and Physiology (B.-R.C., T.L., G.S.) and Department of Electrical Engineering (W.N.), University of Pittsburgh, Pittsburgh, Pa.

Correspondence to Guy Salama, PhD, Department of Cell Biology and Physiology, University of Pittsburgh, School of Medicine, S314 Biomedical Science Tower, 3500 Terrace St, Pittsburgh, PA 15261. E-mail gsalama{at}pitt.edu

The nature and organization of electrical activity during ventricular fibrillation (VF) are important and controversial subjects dominated by 2 competing theories: the wavebreak and the dominant mother rotor hypothesis. To investigate spatiotemporal characteristics of ventricular fibrillation (VF), transmembrane potentials (V_m) were recorded from multiple sites of perfused rabbit hearts using a voltage-sensitive dye and a photodiode array or a CCD camera, and the time-frequency characteristics of V_m were analyzed by short-time fast Fourier transform (FFT) or generalized time-frequency representation with a cone-shaped kernel. The analysis was applied to all pixels to track VF frequencies in time and space. VF consisted of blobs, which are groups of contiguous pixels with a common frequency and an ill-defined shape. At any time t, several VF frequency blobs coexisted in the field of view, and the number of coexisting blobs was on average 5.9±2.1 (n=8 hearts) as they appeared and disappeared discontinuously with time and were not fixed in space. The life span of frequency blobs from birth to either annihilation or breakup to another frequency had a half-life of 0.39±0.13 second (n=4 hearts). The Ca²⁺ channel blocker nifedipine increased the stability of VF frequencies and reduced the number of frequency blobs progressing to a single frequency. In conclusion, VF consists of dynamically changing frequency blobs, which have a short life span and can be modified by pharmacological interventions, suggesting that VF is maintained by dynamically changing multiple wavelets.

Key Words: ventricular fibrillation • ventricular tachycardia • time-frequency analysis • optical mapping • L-type Ca²⁺ channel

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