Recognition of ventricular fibrillation tachycardia from electrogram analysis

Recognition of ventricular fibrillation (VF) and tachycardia (VT) and differentiating life-threatening situations from physiological high rhythms remains a difficult problem. In order to improve detection ability, electrogram analysis was performed using three different methods: the autocorrelation function (ACF), the probability-density function (PDF) and the power-spectrum (fast Fourier transform). During the implantation of an automatic defibrillator in 11 patients, electrograms were obtained from a bipolar electrode in the right ventricle, from an intracardiac spring-epicardial patch, and the ECG. Aortic pressure (AP) was also recorded. VT and VF were induced using AC current or programmed stimulation. Each sinus rhythm (SR) and VF episode could be properly identified using either analysis method. The frequency spectra during VF (peak in the band 4-6 Hz) were significantly different from SR (peaks at heart rate and harmonics). Some VT were missed using ACF and/or PDF. Including AP in the detection algorithm allowed a 100% recognition. The results indicate that all electrogram analysis methods perform well for reliable discrimination between SR and VF but are not very successful in differentiating physiologic VT from life-threatening rhythms