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In the figure below, the three lead ECG on the left shows the initiation of an endless loop tachycardia in a patient with a unipolar DDD pacemaker when the skin over the device was touched at the arrow (low rate 70 ppm, upper rate 150 ppm, atrioventricular delay 170 ms, postventricular atrial refractory period 200 ms). The atrial channel sensed static electricity and and triggered a ventricular output. The absence of native atrial activity before the paced ventricular beat permitted retrograde ventriculoatrial conduction with initiation of tachycardia. Static electricity or triboelectric signals may account for mysterious oversensing by unipolar pacemakers. When the relative humidity is quite low, an observer, especially when wearing rubber shoes, may gather considerable static electricity when entering a carpeted room. Touching the patient's skin over a unipolar pacemaker may release sufficient static voltage to be sensed by a unipolar pacemaker. A signal of several millivolts may be sensed by both channels of a DDD(R) pacemaker and cause inhibition. A smaller signal will be sensed selectively by the atrial channel and trigger a ventricular stimulus as in this case. Triboelectric artefacts may cause puzzling diagnostic problems because they often resemble pacemaker stimuli as shown at the arrow in the three lead ECG on the right recorded from another patient with a unipolar DDD pacemaker. Distortion of the T wave by the applied voltage compounds the situation by producing a pattern that mimicks atrial capture by the triboelectric signal or false atrial stimulus. Two recent reviews on interference with pacemakers made no mention of triboelectric phenomena.
