Tachyarrhythmia detection by implantable defibrillator

A previously published sequential hypothesis testing (SHT) algorithm (see Z. Yi-Sheng and N.V. Thakor, Proc. IEEE 19th Ann. Conf. Eng. Med. Biol. Soc., p.918-19, 1988) is extended to the problem of the discrimination of superventricular tachycardia (SVT) and ventricular tachycardia (VT) signals by an automatic implantable cardioverter/defibrillator. The SHT algorithm compares a likelihood function against the detection thresholds at successive 1-s stages. It allows the desired accuracy to be preset and attains higher accuracy levels only at the cost of increased detection time. The implementation of the algorithm and experimental results are described. The results show that the SHT algorithm correctly discriminates most cases of SVT and VT when the rates in the atrial and ventricular leads differ. When the rates are comparable the time delay between a beat in the atrial lead and the ventricular lead is determined. In the case of SVT the delay is always positive, whereas for VT with retrograde conduction it is zero or negative