Noise Artifacts Detected in a Pacemaker: What is the Source?

Case Description

A 10-year-old girl with an epicardial VVI pacemaker system for cardioinhibitory syncope was seen in routine follow-up, and the high rate counter showed multiple detections from three months prior. Figures 1 and 2 are examples of the non-physiologic signals shown as high rate detections; in some instances, they were seen as noise reversion. The patient had been asymptomatic and could not recall what she was doing during the episodes. Could these be signs of lead dysfunction, electronic interference, or an amplifier issue?

Lead thresholds and impedance trends were stable. The patient and family could neither recall any specific electronics that the patient may have been using other than an iPad, nor had she been in any swimming pool or hot tub. Provocative testing was performed with patient stretching, twisting, and bending over, but we were unable to produce any lead noise artifacts. Despite these negative findings, the pacemaker manufacturer’s technical specialist was still concerned that this may be a lead problem. Thus, we elected to monitor and have the patient return in one month to recheck the counter.

When the family discussed the issue with their extended family, it was discovered that the patient’s grandparent had allowed the patient to use a transcutaneous nerve stimulator (TENS; DR-HO’s^® Pain Therapy System) when she had a sore back from playing hockey. Thus, the family brought this device into clinic for assessment. It has two large flex tone electrode pads (12 cm x 8 cm) connected to a battery-operated stimulator that delivers an auto-modulating electrical current (1.0 to 250 Hz), with three mode settings and four intensity levels. When the two electrode pads were placed on the left and right shoulder blades, the pacemaker sense amplifier showed small regular artifacts whose amplitude was not detected by the pacemaker at any of the intensity settings, while the electrogram (EGM) channel showed very subtle artifact (Figure 3). When the right electrode pad was moved to the right lower waist and the stimulator setting at the lowest intensity, both the EGM and sense amplifier channels showed high frequency noise that was sensed (Figure 4). This was consistent with the noise detected in the counter that resulted in noise reversion asynchronous pacing, as shown in Figure 2.

Discussion

We were able to demonstrate that the high rate detections and noise were due to use of the TENS device. In addition, the location of the electrode placement increased the likelihood of interfering with pacemaker function when one of the electrodes was moved closer to the abdomen where the pacemaker is. The high rate and noise reversion episodes in the counter were suspicious for electromagnetic interference (EMI) due to the regular on (3 second) and off (3 second) cycles of noise interference. This would not be typical of lead noise, make-break fracture, or sense amplifier issue, as these problems would tend to be more random and intermittent. This case highlights the importance of differentiating the pattern of signals between lead noise vs EMI to avoid misdiagnosis. It is also important to educate not only the family but also the pediatric patient to keep electronics and magnets at least 6 inches away as well as to avoid using any devices that deliver electrical current to the body. 

Disclosures: The authors have no conflicts of interest to report regarding the content herein.

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