SJM PM2210 - Issues

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SJM PM2210
ISSUES

Paradoxical Atrial Undersensing: Noise Rate Reversion or
Amplifier Ringing?
BERRY M. VAN GELDER, PH.D.,
∗
WALDY VAN DEN BROEK, B.S.,†
FRANK A. BRACKE, M.D., PH.D.,
∗
and ALBERT MEIJER, M.D., PH.D.
∗
From The
∗
Catharina Hospital, Eindhoven, The Netherlands; and †MEDTRONIC Trading NL, B.V., Heerlen, The Netherlands
Paradoxical Atrial Undersensing. Atrial tachy-arrhythmias may give rise to mode switching or
noise rate reversion in dual-chamber pacemakers. In case of high amplitude of the atrial electrogram
during tachycardia, a paradoxical behavior of atrial sensitivity programming can be observed. Two patients
with implanted dual-chamber pacemakers showed intermittent and complete loss of atrial sensing during
atrial tachycardia during device programming to a higher atrial sensitivity setting. This phenomenon is
caused by amplifier ringing and can be considered as a state of amplifier saturation, which disables atrial
sensing in spite of the high amplitude of the atrial signal. In patients with high amplitude of the atrial
electrogram during atrial tachycardia, a paradoxical behavior of sensitivity programming resulting in
atrial undersensing can be observed. (J Cardiovasc Electrophysiol, Vol. 17, pp. 1371-1374, December 2006)
paradoxical atrial undersensing, amplifier ringing, high-amplitude atrial electrogram, noise rate reversion
Introduction
Inappropriate ventricular pacing response in dual-
chamber devices caused by atrial arrhythmias can be pre-
vented by a mode switching algorithm. The mode switch is
activated when the atrial rate higher than a (programmable)
limit is detected in the atrial channel. For proper mode switch
function, it is essential that the atrial channel senses the atrial
depolarization during tachycardia. The choice of a relatively
low sensitivity may lead to undersensing by fluctuations in
P-wave amplitudes due to physiological changes or to the
lower amplitude of the signal during atrial arrhythmias.
1,2
Selection of the atrial sensitivity setting for proper sensing
during atrial arrhythmias at the time that the patient is still in
sinus rhythm may be difficult, and often a relative high sen-
sitivity is chosen to assure sensing of the atrial arrhythmia,
leading to appropriate mode switching. A high sensitivity
setting in the atrial channel also has some drawbacks. It may
lead to inappropriate mode switching due to far-field R-wave
sensing,
3,4
but also to DOO pacing due to noise rate rever-
sion
5
and complete ignorance of atrial signals by amplifier
ringing.
6
In this article, we present two cases of amplifier
ringing leading to complete atrial undersensing at high atrial
sensitivity settings.
Case report
Patient 1
A 67-year-old male had a Medtronic Kappa 701, dual-
chamber pacemaker implanted because of complete atrioven-
tricular (A-V) block after aortic valve replacement in 1998. A
Medtronic 4024 bipolar lead was implanted in the right ventric-
ular apex and a Medtronic 4524 bipolar lead in the right atrial
Address for correspondence: Berry M. Van Gelder, Ph.D., Department of
Cardiology, Catharina Hospital, Michelangelolaan 2, 5623 EJ Eindhoven,
The Netherlands. Fax: +31-40-2447885; E-mail: carlgr@cze.nl
Manuscript received 24 April 2006; Revised manuscript received 7 July
2006; Accepted for publication 10 July 2006.
doi: 10.1111/j.1540-8167.2006.00597.x
appendage (Medtronic, Inc., Minneapolis, MN, USA). The stim-
ulation threshold measured at the ventricular lead was 0.4 V, 0.9
mA and the amplitude of the intracardiac electrogram (EGM)
was 7.0 mV. The stimulation threshold measured at the atrial
lead was 0.3 V, 0.8 mA and the amplitude of the intracardiac
EGM was 9.8 mV. A total of 5 years after implant, the patient
developed atrial flutter for which he was treated with a right
atrial isthmus ablation. Recently, the patient presented with a
history of “fast pulse” and palpitations. The atrial EGM re-
vealed an atrial tachycardia with a cycle length of 160 msec;
the pacemaker was in mode switch (Fig. 1). However, the pace-
maker diagnostics showed predominant fast ventricular pacing
rates up to the programmed upper rate limit of 130 ppm (Fig.
2A). The pacemaker was programmed in the rate-responsive
mode, but the sensor indicated rate profile excluded abnor-
mal sensor behavior as the cause of rapid ventricular pacing
(Fig. 2B). Inappropriate atrial tracking without mode switch-
ing was one of the remaining diagnoses. Therefore, the pacing
system was programmed to higher atrial sensitivity, from 0.5
mV to 0.18 mV. At this setting, the ECG showed A-V sequential
pacing at the lower rate of 70 ppm. The marker annotations
showed no atrial sense events but only atrial pace events as rec-
ognized from the surface ECG (Fig. 3). Decreasing atrial sensi-
tivity from 0.18 to 0.25, 0.35 and 0.50 mV, respectively, gradually
restored normal function with intermittent atrial sensing at 0.25
and 0.35 mV and normal atrial sensing with mode switching at
0.5 mV.
Because of the high amplitude of the atrial signal (4.5–6.5
mV) during tachycardia the sensitivity was programmed to 1.0
mV. This setting relieved the patient’s symptoms of “fast pulse”
and palpitations during follow-up.
Patient 2
A 42-year-old male had a Medtronic Enpulse E2DR01, dual-
chamber pacemaker implanted because of sick sinus syndrome
with episodes of atrial tachycardia. A Medtronic 5092 bipo-
lar lead was implanted in the right ventricular apex and a
Medtronic 4592 bipolar lead in the right atrial appendage
(Medtronic, Inc.). Pacing and sensing values for the ventric-
ular lead were 1V at 0.4 msec, and the R wave measured with
the device was >22.4mV. Stimulation threshold for the atrial
lead was 0.375 V at 0.4 msec, and all measured P waves by
the device were >2.8 mV. Direct measurement with the pacing








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