Angular velocity: A new method to improve prediction of ventricular fibrillation duration

Abstract

Ventricular fibrillation (VF) is a leading cause of sudden death. Electrical defibrillation is the primary modality of treatment, but evidence is accumulating that its use in the late stages of VF prior to providing ventilation, chest compressions and the administration of appropriate medication is detrimental. In VF of <5min duration a 'shock first' strategy is effective. In VF of >5min duration a 'perfuse first' approach is more effective. Because of the difficulty in determining the duration of VF in the clinical setting we have sought to develop methods which analyze 5s intervals of VF waveform and quickly provide an estimate of duration. Such methods would be useful in directing clinical interventions. Using methods of nonlinear dynamics and fractal geometry we have previously derived a quantitative measure of VF duration, namely the scaling exponent (ScE). In this study we report on a novel method also based on nonlinear dynamics, the angular velocity (AV). By constructing a flat, circular disk-shaped structure in a three-dimensional phase space and measuring the velocity of rotation of the position vector over time, a statistic is developed which rises from 58rad/s at 1min to 79rad/s at 4min and then decreases in a linear manner to 32rad/s at 12.5min. Using ScE and AV probability density estimates, VF of <5min duration can be identified with 90% sensitivity on the basis of a single 5s recording of the waveform. The combination of ScE and AV can be useful in developing strategies for the treatment of VF during the different clinical phases of VF. © 2004 Elsevier Ireland Ltd. All rights reserved.