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Multiple-Sensor Systems for Physiologic Cardiac Pacing

David G. Benditt, MD; Marcus Mianulli, BS, BA; Keith Lurie, MD; Scott Sakaguchi, MD; and Stuart Adler, MD
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From the University of Minnesota, Minneapolis, Minnesota. Requests for Reprints: David G. Benditt, MD, Cardiac Arrhythmia Center (Cardiovascular Division), Box 341 UMHC, University of Minnesota, Minneapolis, MN 55455. Acknowledgments: The authors thank E. Dean Birchfield, MS, and Joseph Fetter, RPEE, for their valuable assistance; and Wendy Markuson, Stephanie Colbert, and Barry L. S. Detloff for manuscript preparation. Dr. Benditt and Mr. Mianulli work as consultants for Medtronic Inc.

Copyright ©2004 by the American College of Physicians

Ann Intern Med. 1994;121(12):960-968. doi:10.7326/0003-4819-121-12-199412150-00010
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Purpose: To review the status of artificial sensors in cardiac pacemakers and the rationale for developing pacing systems that use multiple sensors.

Data Sources: Journal articles published between 1982 and 1993 indexed in MEDLINE using the keywords pacemakers, sensors, and rate-adaptive, as well as abstracts and articles in the authors' personal files.

Study Selection: Articles describing clinical experience with or clinical evaluation of cardiac pacing systems using multiple artificial sensors.

Data Synthesis: Artificial sensors were created to adjust pacing rate reliably in response to changes in levels of physical exertion for patients with sinoatrial disease in whom exercise heart rate response is inadequate (for example, chronotropic incompetence in sinoatrial disease). To achieve this, various artificial sensors were developed and many reports confirm improved exertional tolerance. More recently, sensors have assumed a greater role in cardiac pacemakers. For example, sensors are used to permit automatic adjustment of certain programmable pacemaker settings, such as the atrioventricular interval. In the future, they may also be used to maximize pacemaker longevity by automatically optimizing energy output (voltage, pulse width). No single sensor is ideal for all potential applications, and investigators have advocated using two or more sensors. Several pacemakers that use multiple sensors with different but complementary operating characteristics are already commercially available outside the United States. Although preliminary findings are encouraging, additional clinical experience with these pacemakers is needed to determine their ultimate role in clinical practice.

Conclusion: Simultaneous use of multiple complementary artificial sensors may permit development of cardiac pacemakers that operate more physiologically yet require less specialized medical follow-up.


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Figure 1.
Changes in pacing mode use in North America in the past decade (see[3]).Table 1

The ordinate indicates the percentage of pacemakers of a given pacing mode (see for definitions) that were implanted during the year indicated on the abscissa. There has been a trend toward more frequent use of dual-chamber pacing (DDD and DDDR modes) and a greater reliance on devices with rate-adaptive capability (DDD, DDDR, and VVIR modes). Single-chamber atrial pacing (AAI and AAIR modes) is used infrequently (fewer than 1% implants annually) and therefore is not plotted on this graphic.

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Figure 3.
Two sensors, one relatively fast responder and one slower but more workload proportional, can work together to elicit a more physiologic heart rate response than either would if used alone.

The ordinate indicates pacing rate. The abscissa shows the duration of exercise. The individual sensor responses and the combined response are shown.

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Figure 2.
Oxygen kinetics analysis during abrupt-onset, fixed-workload (subanaerobic) exercise may be useful to distinguish subtle differences in sensor-system operation or programming.O2O2

This type of exercise protocol mimics the transient activities of daily living and therefore may be useful to assess the clinical utility of new pacing systems and their programming. Ultimate peak oxygen consumption levels (V , mL/min, abscissa) are identical in the two panels. However, the times taken to achieve these responses differ. In panel A, V equilibrium is delayed because of a relatively slow chronotropic response. Panel B depicts a more physiologically desirable outcome, with a smaller oxygen deficit and a shorter mean response time (MRT). The region of oxygen deficit at onset of exercise is noted by the shaded area in each panel.

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