Frequency spectra of ventricular tachycardia and sinus rhythm in human intracardiac electrograms-application to tachycardia detection for cardiac pacemakers

Presently available antitachycardia pacemakers detect ventricular tachycardia (VT) by measurement of the period of the intracardiac electrogram (EGM). The resulting inability to differentiate between VT and rapid normal sinus rhythm (NSR) can cause inappropriate pacemaker output, possibly initiating an arrhythmia where none existed previously. It is reported that FFT analysis of matched-pair NSR-VT EGM recordings from 33 patients revealed a mean (+or-SD) NSR-VT difference in the peak amplitude point of 8 (+or-7) Hz and a difference of 18 (+or-18) Hz in the -3 dB point. NSR-VT amplitude differences could be significantly increased by filtering over the range of greatest spectral differences. Variable-passband programmable filters could enhance VT detection in antitachycardia pacemakers.