Adaptive filters for analysis of intra-cardiac signals.

Implantable cardioverters and defibrillators must discriminate malignant ventricular arrhythmias from other supraventricular tachycardias. Electrogram signals are sensed by a single floating endocardial catheter with multiple sensors. The sensors acquire composite atrial and ventricular complexes from atrial and ventricular chambers. Two adaptive filters are utilised to discriminate atrial signals from ventricular signals. The adaptive impulse correlated filter utilises an impulse sequence correlated with the ventricular depolarisations in order to filter the composite signal. This filter should be useful in the analysis of atrial arrhythmias. The adaptive series feedback filter utilises two back-to-back coupled filters to simultaneously extract ventricular depolarisations from one input channel and atrial depolarisations from another channel. This filter should be useful in the analysis of ventricular arrhythmias. Theoretical analysis of the adaptation capabilities of these filters and criteria for convergence are presented. Experimental electrogram recordings are analysed to demonstrate the performance of the two filters. Computational simplicity of these filters makes them particularly suitable for programmable implantable devices.