Automatic Adjustment of Pacing Output in the Clinical Setting
Automatic Adjustment of Pacing Output in the Clinical Setting
Background: AutoCapture (AC) is a programmable feature that enables the pacemaker to both track the capture threshold and automatically adjust the output on a beat-by-beat basis. Although AC safely and significantly reduces the current drainage, some authors have argued that the longevity benefit of such a system is overstated. This study aims to estimate the longevity extension that can be obtained, in the clinical routine, by turning the AC on in comparison to pacemakers programmed to operate at the shipped and manually optimized output.
Methods: We selected 83 consecutive patients who received implanted St Jude's Affinity pacemakers >6 months earlier. Eight patients died or were lost to follow-up and in 9 subjects the AC could not be turned on. In the remaining 66 patients, current drain and estimated longevity were compared in 3 situations: (1) AC on; (2) AC off, optimized programming (100%-150% voltage threshold); (3) AC off, shipped output (3.5 V).
Results: Five patients had large variations (>1 V) of the AC threshold. Current drainage was 8.0 ± 0.9 mA in the AC group, 8.7 ± 1.8 mA with AC off and optimized programming, and 11.3 ± 2.3 mA at shipped output (P < .01). Estimated longevity was significantly extended (P < .01) by AC (12.1 ± 1.0 years) when compared to shipped (8.9 ± 1.7 years) and optimized programming (11.3 ± 1.4 years).
Conclusion: Reprogramming the pacemaker output significantly enhanced its estimated longevity; AC added a moderate but significant extension over manual reprogramming and was associated with increased safety in patients with large ventricular threshold variations.
Pulse generator longevity prolongation has been an important objective in artificial cardiac pacing since its beginning. After major technological advances achieved in the last few decades, prospective studies proved that, through the reprogramming of output settings a few months after implantation, the generator unit life span could be significantly enhanced safely and without loss of capture, as verified by telemetry and 24-hour Holter monitoring. Nonetheless, it is known that pacemakers are frequently never reprogrammed after implantation, which deprives patients with pacemakers of resources available in modern pulse generators and shortens the pulse generator longevity.
AutoCapture (AC) is a programmable feature that allows the recognition of cardiac-evoked response, allowing automatic pacing output adjustment. Several studies have shown that AC can safely reduce current drainage, prolong device longevity, and reduce costs. However, some authors have argued that the longevity benefit of such a system is frequently overstated. Indeed, the majority of the studies were performed using VVIR systems. In DDDR systems, the net benefit obtained from the reduction of the ventricular current drainage by the AC would be hampered by the maintenance of atrial and housekeeping current drainage, because atrial automatic capture is not commercially available. Additionally, this reduction could be partially offset by the incremental current drain required to implement the AC feature. Another challenge in the implementation of AC is accurate assessment in the presence of fusion and pseudofusion beats, which are more common in DDDR pacemakers. In 1999, the first dual-chamber pacemaker system with the AC technology was released, the Affinity DR (Pacesetter, St Jude Medical, Sylmar, Calif). A fusion avoidance algorithm was added to this model to prevent needless current drainage. Few studies have been published about the AC system in the Affinity pacemaker models.
This study aims to estimate the longevity extension that can be obtained, in the clinical routine, by turning on the AC in patients with Affinity pacemakers in comparison to pacemakers programmed to operate at the shipped and manually optimized output.
Background: AutoCapture (AC) is a programmable feature that enables the pacemaker to both track the capture threshold and automatically adjust the output on a beat-by-beat basis. Although AC safely and significantly reduces the current drainage, some authors have argued that the longevity benefit of such a system is overstated. This study aims to estimate the longevity extension that can be obtained, in the clinical routine, by turning the AC on in comparison to pacemakers programmed to operate at the shipped and manually optimized output.
Methods: We selected 83 consecutive patients who received implanted St Jude's Affinity pacemakers >6 months earlier. Eight patients died or were lost to follow-up and in 9 subjects the AC could not be turned on. In the remaining 66 patients, current drain and estimated longevity were compared in 3 situations: (1) AC on; (2) AC off, optimized programming (100%-150% voltage threshold); (3) AC off, shipped output (3.5 V).
Results: Five patients had large variations (>1 V) of the AC threshold. Current drainage was 8.0 ± 0.9 mA in the AC group, 8.7 ± 1.8 mA with AC off and optimized programming, and 11.3 ± 2.3 mA at shipped output (P < .01). Estimated longevity was significantly extended (P < .01) by AC (12.1 ± 1.0 years) when compared to shipped (8.9 ± 1.7 years) and optimized programming (11.3 ± 1.4 years).
Conclusion: Reprogramming the pacemaker output significantly enhanced its estimated longevity; AC added a moderate but significant extension over manual reprogramming and was associated with increased safety in patients with large ventricular threshold variations.
Pulse generator longevity prolongation has been an important objective in artificial cardiac pacing since its beginning. After major technological advances achieved in the last few decades, prospective studies proved that, through the reprogramming of output settings a few months after implantation, the generator unit life span could be significantly enhanced safely and without loss of capture, as verified by telemetry and 24-hour Holter monitoring. Nonetheless, it is known that pacemakers are frequently never reprogrammed after implantation, which deprives patients with pacemakers of resources available in modern pulse generators and shortens the pulse generator longevity.
AutoCapture (AC) is a programmable feature that allows the recognition of cardiac-evoked response, allowing automatic pacing output adjustment. Several studies have shown that AC can safely reduce current drainage, prolong device longevity, and reduce costs. However, some authors have argued that the longevity benefit of such a system is frequently overstated. Indeed, the majority of the studies were performed using VVIR systems. In DDDR systems, the net benefit obtained from the reduction of the ventricular current drainage by the AC would be hampered by the maintenance of atrial and housekeeping current drainage, because atrial automatic capture is not commercially available. Additionally, this reduction could be partially offset by the incremental current drain required to implement the AC feature. Another challenge in the implementation of AC is accurate assessment in the presence of fusion and pseudofusion beats, which are more common in DDDR pacemakers. In 1999, the first dual-chamber pacemaker system with the AC technology was released, the Affinity DR (Pacesetter, St Jude Medical, Sylmar, Calif). A fusion avoidance algorithm was added to this model to prevent needless current drainage. Few studies have been published about the AC system in the Affinity pacemaker models.
This study aims to estimate the longevity extension that can be obtained, in the clinical routine, by turning on the AC in patients with Affinity pacemakers in comparison to pacemakers programmed to operate at the shipped and manually optimized output.
