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

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 stage of VF prior to providing ventilation, chest compressions and the administration of appropriate medication is detrimental. In VF of <5 min duration a 'shock first' strategy is effective. In VF of 5> min 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 method which analyze 5 s 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 58 rad/s at 1 min to 79 rad/s at 4 min and then decreases in a linear manner to 32 rad/s at 12.5 min. Using ScE and AV probability density estimated, VF of <5 min duration can be identified with 90% sensitivity on the basis of a single 5 s recording of the waveform. The combination of ScE and AV can be used in developing strategies for the treatment of VF during the different clinical phases of VF.