Author + information
- Received July 27, 1987
- Revision received October 28, 1987
- Accepted November 11, 1987
- Published online April 1, 1988.
- Gerd Frohlig, MD∗,
- Holger Schwerdt, MD, DEng,
- Hermann Schieffer, MD and
- Ludwig Bette, MD
- ↵∗Address for reprints: Gerd Frohlig, MD, Medizinische Universitatsklinik, Innere Medizin III (Cardiologie), D-6650 Homburg, West Germany.
To give some explanation for atrial malsensing in dual chamber pacing that occurs Only during exercise, atrial electrograms from 33 patients were telemetrically recorded and analyzed in both the time and frequency domains. During exercise, an overall decrease from 6.4 ± 1.9 to 5.6 ± 1.9 mV (−11%) in the atrial signal amplitude was noted. Despite considerable variability among patients, marked changes occurred in 15 patlents whose signals diminished by 11 to 49%. Slew rates showed a similar decrease from 1.35 ± 0.45 to 1.18 ± 0.45 V/s (−10.8%), with individual changes of as much as −51%. Signal attenuation in the time domain correlated well with frequency data, exhibiting a highly significant reduction of signal energy between 25 and 105 Hz. However, spectral distribution changed from rest to exercise, with a relative increase of signal energy in the range between 5 and 25 Hz and a decrease at higher frequencies.
Individual changes differed widely when low (15 to 65 Hz) and high (65 to 115 Hz) frequencies were compared, but in a group of 11 patients signal attenuation in the high frequency band was more pronounced (−45%) than in the low frequency band (−23%). The clinical impact of the change in frequency distribution during ergomctry was visualized by computer simulation of two different (low and high bandpass) filters. Although in individual patients, both characteristics may be favorable with respect to atrial sensing, it was observed in 11 patients that high pass filtering attenuates signal amplitudes by 10 to 24% in excess of the variation without filtering.
It is concluded that in most patients, amplitude reduction in the atrial electrogram may be observed during exercise and may even be accentuated by narrow bandpass filtering because variations do occur in the distribution of signal frequencies. This is of concern in pacemaker design and in the concepts of pacemaker therapy.
- Received July 27, 1987.
- Revision received October 28, 1987.
- Accepted November 11, 1987.