Device‐Specific Responses to Pacemaker‐Mediated Arrhythmia in Patients With Prolonged Ventriculoatrial Conduction: A Comparative Simulation Study

Figures

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  FIGURE 1. (A) PMT Response (Abbott). This figure shows a pacemaker‐mediated tachycardia (PMT) episode stored in the memory of the Abbott device. The ventriculoatrial conduction (VAC) that occurred after the fourth ventricular pacing (VP) triggered the PMT. After 8 beats with A‐A intervals faster than the set PMT detection rate, the device evaluates the stability of the interval between VP and subsequent atrial sensing (AS). If this interval is stable and remains constant even when the next sensed AV delay is modulated (red rectangle), the device detects the presence of PMT. The device suppresses VP and terminates PMT with atrial pacing (AP) after AS (green rectangle). To detect PMT induced under VAC 550 ms, the sensed AV delay should be set short, and the actual PMT rate must be above the set PMT detection rate. (B) PMT Protection (BIOTRONIK). If the VP‐AS interval is shorter than the VA criterion for 8 consecutive beats and the deviation is small, the device checks whether changing the sensed AV delay (asterisk) on the next beat affects the VAC time. If it does not change, the next post‐ventricular atrial refractory period (PVARP) is extended 50 ms beyond the VA criterion, terminating the…

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  FIGURE 2. Operation similar to VVI. Although the VAC is marked as “Ar”, the MicroPort CRM's WARAD feature does not function in DDI mode; therefore, it is effectively atrial sensing. As a result, atrial pacing is inhibited, and the AV interval is determined by the VAC time and the lower rate limit, resulting in VVI‐like operation. Ap: Atrial pacing, Ar: Atrial sensing in DDI mode, Vp: Ventricular pacing.

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  FIGURE 3. (A) Uniformly shortened PAV after the delayed AP. The APs following the VAC are spaced at regular intervals. The paced AV delay (PAV) after the delayed AP (asterisks) is shorter than the programmed one. In devices using V‐V timing, the V‐V intervals (double‐headed arrows) remain constant. AP: Atrial pacing, AS: Atrial sensing within the PVARP, VP: Ventricular pacing. (B) The PAV varied alternately with every other beat. After the AP delay, the PAV alternates between shortened beats (asterisks) and programmed beats, with intermittent V‐V interval prolongation. The AP‐AP interval of the beat with the prolonged V‐V interval (double‐headed arrows) matched the set lower rate limit, and the following PAV was as programmed, suggesting that it was actuated by A‐A timing. AP: Atrial pacing, AR: Atrial sensing within the PVARP, VP: Ventricular pacing. (C) RNRVAS due to lack of post‐AR AP delay function. When the retrograde P wave and AP are in proximity, the stimulus is ineffective (asterisks) as it falls during the atrial refractory period. Devices without the post‐AR AP delay function will pace at the lower rate limit unless AS is counted. During the PAV and VAC time, the atrium recovers…

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  FIGURE 4. Pacing cycle prolonged beyond the lower rate limit. This figure shows the AP delays following atrial sensing within the refractory period (AR) in the BIOTRONIK device. It is standard behavior to skip the AP and proceed directly to the AR‐VP sequence if the AP delay would prolong the V‐V interval. However, in BIOTRONIK devices, if the sum of the VAC time, post‐AR AP delay, and the shortest PAV (asterisks, 75 ms) exceeds the programmed lower rate limit, the pacing cycle is prolonged beyond the lower rate limit. Ap: Atrial pacing, As (PVARP): Atrial sensing within the PVARP, Vp: Ventricular pacing.