DEVICE ROUNDS
Juxtaposition of Automatic Mode Switching and Tachycardia-Terminating Algorithms in a Dual-Chamber Implantable Cardioverter Defibrillator S. SERGE BAROLD, M.D.* and ROLAND X. STROOBANDT, M.D.† From the *Florida Heart Rhythm Institute, Tampa, Florida; and †Heart Centre, University Hospital of Ghent, Ghent, Belgium
defibrillation - ICD, pacing
A 65-year-old man received his first implantable cardioverter defibrillator (ICD) in 2000 and his third ICD in 2010 (dual-chamber St. Jude, St. Jude Medical, Sylmar, CA, USA, Current Accel DR1 ). In July 2011, he presented with many new onset episodes of pacemaker-mediated tachycardia (PMT) and automatic mode switching (AMS). One AMS episode occurred in juxtaposition with a PMT (Figs. 1 and 2). The ICD parameters included: Mode DDDR, low rate = 50 pulses/min (ppm), upper rate = 120 ppm, paced atrioventricular (AV) delay = 170 ms, sensed AV delay = 110 ms, rate-adaptive postventricular atrial refractory period (PVARP) = 275 ms (minimum 225 ms, high setting), tachycardia detection rate interval for AMS = 333 ms (rate 180 beats/min), and AMS base rate = 70 ppm. The stored atrial electrograms revealed oversensed atrial false signals (Fig. 1). The atrial lead impedance was normal. The patient had always exhibited stable retrograde ventriculoatrial (VA) conduction of 240 ms, which had been consistently contained by an unchanged PVARP of 275 ms as above. The device interpreted the sensed atrial false signals as an increase in atrial rate and shortened the rate-adaptive PVARP which, in turn, permitted sensing of retrograde P waves that initiated PMT. The triggering of AMS by noise on the atrial lead and the mechanism of PVARP abbreviation in this specific patient was previously reported.1,2 This communication describes the previously unpublished interplay of the AMS and PMT algorithms in this specific patient. Why did AMS occur immediately after the algorithmic termination of PMT? How does juxtaposition of these two responses reveal the interaction and characteristics of the underlying algorithms? Address for reprints: S. Serge Barold, M.D., Florida Heart Rhythm Institute, Tampa, Florida; e-mail: [email protected] Received September 16, 2013; accepted September 24, 2013. doi: 10.1111/pace.12317
Interpretation of the Recordings Figure 1 shows stored tracings with the atrial electrogram (A) on top and the ventricular electrogram (V) beneath the atrial electrogram. Atrial false signals occurred irregularly, causing interference in the atrial electrogram. The horizontal lines at the bottom of each tracing depict the duration of the blanking and refractory periods: the atrial intervals are above the ventricular intervals. The thicker lines show the atrial and blanking periods. The PVARP is represented by the thin line beyond the postventricular atrial blanking period (PVAB; thick line). False signals were detected in the atrial refractory period where they are represented in the atrial marker channel by short upward vertical lines. False signals were detected beyond the atrial blanking periods, in the PVARP and in the AV delay. In the upper recording, VIP means ventricular intrinsic preference .3 The VIP feature was programmed for three cycles at 200 ms. The first atrial event started a partially extended AS-VS delay (AS = atrial-sensed event and VS = ventricular-sensed event). The second atrial event started a fully extended AS-VP event (VP = ventricular-paced) interval of (110 + 200) = 310 ms. The third, fourth, and fifth atrial events initiated AP-VS (AP = atrial-paced event) intervals that were also partially extended. The sixth atrial interval consisted of an AS-VP interval that is fully extended at (110 + 200) = 310 ms. In the upper recording, it appears that a sensed atrial false signal initiated a PMT by permitting retrograde VA conduction from the VP event. The rate of the PMT is 120 ppm identical to the programmed upper tracking rate (interval = 500 ms). The device made the diagnosis of PMT in the ninth cycle (bottom recording) by prolonging the test AV delay by 50 ms (arrow pointing downward in lower recording).4 The VA interval remained unchanged, indicating a positive diagnosis. The device then looked for the next AS event and completed the algorithm in two ways: (1) The first AS event after the test AV delay triggered a vertical
©2013 Wiley Periodicals, Inc. 1408
October 2014
PACE, Vol. 37
JUXTAPOSITION OF TWO PACEMAKER ALGORITHMS
Figure 1. Juxtaposition of pacemaker-mediated tachycardia and activation of automatic mode switching (AMS). AP = atrial-paced event; AS = atrial-sensed event; PMT = pacemaker-mediated tachycardia; VP = ventricular-paced event; VS = ventricular-sensed event. See text for details.
line (first trigger marker), indicating the diagnosis of PMT. VP was inhibited after this AS event with resulting PMT termination, and (2) an AP event (slanted arrow) was delivered 330 ms from the AS event that was unaccompanied by a VP event. This AP event is part of the PMT algorithm and is delivered 330 ms after the AS event associated with termination of the PMT (first trigger line). AP is followed by an AS event (*). This AS was followed by an atrial event detected in the atrial refractory period in the AV delay that was initiated by the preceding AS event (*) (Fig. 2, cycle 4). Detection of an atrial signal in the atrial refractory period is not associated with a telemetered symbolic marker. During AMS in the DDI mode, the ventricular paced rate was 70 ppm and there was regular retrograde VA conduction interval with a duration of (855 – 617) 238 ms to (859 – 617) 242 ms. In this case, the rate-adaptive PVARP shortened the VA interval from 275 ms (seen in the DDI mode) to at least 238 ms or even shorter, permitting the initiation of PMT.2 Note that, during AMS, the PVARP becomes equal to the PVAB. When calculating
PACE, Vol. 37
the duration of the atrial intervals for AMS activation, the device uses AP events and all atrial events beyond the atrial blanking periods. Discussion The unusual juxtaposition of a true PMT and AMS has not been previously reported. AMS and PMT are associated with entirely different algorithms.3 The observations raise the question as to whether the two algorithms are in some way connected. The PMT algorithm monitors rate and the ventriculoatrial (V pace-atrial sense) intervals where the sensed atrial events must be outside the PVARP.3,4 The filtered atrial rate interval (FARI) of St. Jude devices that drives the AMS algorithm is always updating by analyzing all the atrial intervals or events outside the atrial blanking periods regardless of the state of PMT detection or termination. It is difficult to assess the contribution of the various atrial intervals to the FARI. Atrial intervals are either longer or shorter than the prevailing FARI.5 A long interval (>FARI) lengthens the FARI by 23 ms whereas a short interval (
Juxtaposition of Automatic Mode Switching and Tachycardia-Terminating Algorithms in a Dual-Chamber Implantable Cardioverter Defibrillator S. SERGE BAROLD, M.D.* and ROLAND X. STROOBANDT, M.D.† From the *Florida Heart Rhythm Institute, Tampa, Florida; and †Heart Centre, University Hospital of Ghent, Ghent, Belgium
defibrillation - ICD, pacing
A 65-year-old man received his first implantable cardioverter defibrillator (ICD) in 2000 and his third ICD in 2010 (dual-chamber St. Jude, St. Jude Medical, Sylmar, CA, USA, Current Accel DR1 ). In July 2011, he presented with many new onset episodes of pacemaker-mediated tachycardia (PMT) and automatic mode switching (AMS). One AMS episode occurred in juxtaposition with a PMT (Figs. 1 and 2). The ICD parameters included: Mode DDDR, low rate = 50 pulses/min (ppm), upper rate = 120 ppm, paced atrioventricular (AV) delay = 170 ms, sensed AV delay = 110 ms, rate-adaptive postventricular atrial refractory period (PVARP) = 275 ms (minimum 225 ms, high setting), tachycardia detection rate interval for AMS = 333 ms (rate 180 beats/min), and AMS base rate = 70 ppm. The stored atrial electrograms revealed oversensed atrial false signals (Fig. 1). The atrial lead impedance was normal. The patient had always exhibited stable retrograde ventriculoatrial (VA) conduction of 240 ms, which had been consistently contained by an unchanged PVARP of 275 ms as above. The device interpreted the sensed atrial false signals as an increase in atrial rate and shortened the rate-adaptive PVARP which, in turn, permitted sensing of retrograde P waves that initiated PMT. The triggering of AMS by noise on the atrial lead and the mechanism of PVARP abbreviation in this specific patient was previously reported.1,2 This communication describes the previously unpublished interplay of the AMS and PMT algorithms in this specific patient. Why did AMS occur immediately after the algorithmic termination of PMT? How does juxtaposition of these two responses reveal the interaction and characteristics of the underlying algorithms? Address for reprints: S. Serge Barold, M.D., Florida Heart Rhythm Institute, Tampa, Florida; e-mail: [email protected] Received September 16, 2013; accepted September 24, 2013. doi: 10.1111/pace.12317
Interpretation of the Recordings Figure 1 shows stored tracings with the atrial electrogram (A) on top and the ventricular electrogram (V) beneath the atrial electrogram. Atrial false signals occurred irregularly, causing interference in the atrial electrogram. The horizontal lines at the bottom of each tracing depict the duration of the blanking and refractory periods: the atrial intervals are above the ventricular intervals. The thicker lines show the atrial and blanking periods. The PVARP is represented by the thin line beyond the postventricular atrial blanking period (PVAB; thick line). False signals were detected in the atrial refractory period where they are represented in the atrial marker channel by short upward vertical lines. False signals were detected beyond the atrial blanking periods, in the PVARP and in the AV delay. In the upper recording, VIP means ventricular intrinsic preference .3 The VIP feature was programmed for three cycles at 200 ms. The first atrial event started a partially extended AS-VS delay (AS = atrial-sensed event and VS = ventricular-sensed event). The second atrial event started a fully extended AS-VP event (VP = ventricular-paced) interval of (110 + 200) = 310 ms. The third, fourth, and fifth atrial events initiated AP-VS (AP = atrial-paced event) intervals that were also partially extended. The sixth atrial interval consisted of an AS-VP interval that is fully extended at (110 + 200) = 310 ms. In the upper recording, it appears that a sensed atrial false signal initiated a PMT by permitting retrograde VA conduction from the VP event. The rate of the PMT is 120 ppm identical to the programmed upper tracking rate (interval = 500 ms). The device made the diagnosis of PMT in the ninth cycle (bottom recording) by prolonging the test AV delay by 50 ms (arrow pointing downward in lower recording).4 The VA interval remained unchanged, indicating a positive diagnosis. The device then looked for the next AS event and completed the algorithm in two ways: (1) The first AS event after the test AV delay triggered a vertical
©2013 Wiley Periodicals, Inc. 1408
October 2014
PACE, Vol. 37
JUXTAPOSITION OF TWO PACEMAKER ALGORITHMS
Figure 1. Juxtaposition of pacemaker-mediated tachycardia and activation of automatic mode switching (AMS). AP = atrial-paced event; AS = atrial-sensed event; PMT = pacemaker-mediated tachycardia; VP = ventricular-paced event; VS = ventricular-sensed event. See text for details.
line (first trigger marker), indicating the diagnosis of PMT. VP was inhibited after this AS event with resulting PMT termination, and (2) an AP event (slanted arrow) was delivered 330 ms from the AS event that was unaccompanied by a VP event. This AP event is part of the PMT algorithm and is delivered 330 ms after the AS event associated with termination of the PMT (first trigger line). AP is followed by an AS event (*). This AS was followed by an atrial event detected in the atrial refractory period in the AV delay that was initiated by the preceding AS event (*) (Fig. 2, cycle 4). Detection of an atrial signal in the atrial refractory period is not associated with a telemetered symbolic marker. During AMS in the DDI mode, the ventricular paced rate was 70 ppm and there was regular retrograde VA conduction interval with a duration of (855 – 617) 238 ms to (859 – 617) 242 ms. In this case, the rate-adaptive PVARP shortened the VA interval from 275 ms (seen in the DDI mode) to at least 238 ms or even shorter, permitting the initiation of PMT.2 Note that, during AMS, the PVARP becomes equal to the PVAB. When calculating
PACE, Vol. 37
the duration of the atrial intervals for AMS activation, the device uses AP events and all atrial events beyond the atrial blanking periods. Discussion The unusual juxtaposition of a true PMT and AMS has not been previously reported. AMS and PMT are associated with entirely different algorithms.3 The observations raise the question as to whether the two algorithms are in some way connected. The PMT algorithm monitors rate and the ventriculoatrial (V pace-atrial sense) intervals where the sensed atrial events must be outside the PVARP.3,4 The filtered atrial rate interval (FARI) of St. Jude devices that drives the AMS algorithm is always updating by analyzing all the atrial intervals or events outside the atrial blanking periods regardless of the state of PMT detection or termination. It is difficult to assess the contribution of the various atrial intervals to the FARI. Atrial intervals are either longer or shorter than the prevailing FARI.5 A long interval (>FARI) lengthens the FARI by 23 ms whereas a short interval (
