Incorrect Holter-ECG analysis caused by the pacemaker delivering small high-frequency currents for thoracic impedance measurement.

In an 86-year-old woman who had been treated for sick sinus syndrome, the small high-frequency current delivered by pacemaker in order to measure the minutes ventilation for utilizing the rate-response mode was transiently over-sensed on the Holter electrocardiogram. Although her pacing system was working appropriately, the numbers of the paced beats on the automatic Holter analysis were undercounted (from >60% to <5%) during the over-sensing periods because these currents were recognized as multiple pacing spikes. Physicians need to pay attention to such multiple pacing spike markers, because these can be a cause of unreliable results of the Holter analysis. <Learning objective: Paying attention to multiple pacing spike markers on Holter electrocardiogram is clinically important in patients treated by a rate-response pacemaker. This is because (1) this does not imply the malfunction of the pacemaker system, and (2) results from automatic Holter analysis would not be reliable during the period when these multiple pacing markers were recorded.>.