Pseudomalfunction Caused by Accelerated Junctional Rhythm during Managed Ventricular Pacing

概要

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Managed Ventricular Pacing (MVP) is designed to minimize the percentage of ventricular pacing for reducing demerits. This case describes the complex feature of MVP operation during an accelerated junctional rhythm. A 70-year-old man with sick sinus syndrome underwent implantation of a DDD pacemaker (Medtronic EnRhythm, Medtronic Inc., St. Paul, MN, USA) and has been checked up regularly. The pacemaker was programed in a MVP mode (AAIR-DDDR) with a rate of 70–120 ppm, Paced AV delay was programmed to 300 ms and Sensed AV delay was 270 ms. During an accelerated junctional rhythm faster than the lower rate limit, the pacing mode had automatically changed AAIR to DDDR due to the crosstalk response containing distinctively within the programming of this device. In this situation, we found 3 types of AV delay, 80 ms; ventricular back up pacing induced by crosstalk response, 110 ms; ventricular safety pacing, and 300 ms; programming paced AV delay due to junctional beats occurring during the ventricular blanking period. The third mechanism induced a ventricular pacing on the top of T wave (so called “spike on T” phenomenon). Paced AV delay was re-programmed to 180 msec. These 3 factors (crosstalk response, ventricular safety pacing, ventricular blanking period) delivered each different AV delay in this case.