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Medical Devices

Interaction Between Minute Ventilation Rate-Adaptive Pacemakers and Cardiac Monitoring and Diagnostic Equipment


October 14, 1998


Dear Colleague:

This is to alert you that minute ventilation rate-adaptive implantable pacemakers can occasionally interact with certain cardiac monitoring and diagnostic equipment, causing the pacemakers to pace at their maximum programmed rate. Minute ventilation rate-adaptive pacemakers currently marketed include Telectronics’ (St. Jude Medical) META and Tempo series, Medtronic’s Legend Plus and Kappa 400 series, and ELA Medical’s Chorus RM and Opus RM series.



Over the past year, several incidents have been reported in the medical literature in which minute ventilation rate-adaptive pacemakers paced at their maximum rate when patients were connected to cardiac monitoring and diagnostic equipment.1-3 None of these instances resulted in a patient death or injury (pacing returned to normal when the monitors were disconnected from patients). However, we are concerned that this unexpected rise in the pacing rate could be misdiagnosed as clinically significant tachycardia, resulting in unnecessary therapy, or that patients with compromised cardiac reserve (e.g., with unstable angina or myocardial infarction) may poorly tolerate the higher pacing rates.


Cause of problem

Minute ventilation is sensed in rate-adaptive pacemakers by a technology known as bioelectric impedance measurement (BIM). Many medical devices in addition to pacemakers use this technology. When one of these devices is used on a patient with an active, minute ventilation rate-adaptive pacemaker, the pacemaker may erroneously interpret the mixture of BIM signals created in the patient, resulting in an elevated pacing rate. Examples of commonly used devices that may use BIM technology and thus could affect minute ventilation pacemaker rates are cardiac monitors, echocardiograph equipment, apnea monitors, respiration monitors, and external defibrillators.



The following precautions should be taken into consideration for patients with minute ventilation rate-adaptive pacemakers:

1. Deactivate minute ventilation sensor. When treating a patient with an implanted minute ventilation rate-adaptive pacemaker, be aware that an increase in the cardiac rate may be due to interaction between the pacemaker and another medical device attached to the patient. Consider changing the operating mode of the pacemaker to a minute ventilation insensitive mode before performing the procedure. Consult the pacemaker manufacturer’s instructions for this.

2. Select appropriate maximum pacing rate. Since interference is most likely to cause serious effects if the pacemaker is programmed at a maximum rate not tolerated by the patient, be sure to periodically check that the set maximum rate is still appropriate for the patient during pacemaker follow-up visits.

3. Inform appropriate pacemaker patients (or their families) of the potential for this interaction. They would then be aware of the potential for unexpected rises in the pacing rate when the patient undergoes medical procedures that use BIM devices.


Reporting adverse events

FDA is interested in obtaining data on malfunctions and adverse events involving minute ventilation rate-adaptive pacemakers and other BIM devices. Practitioners who are employed by health care facilities that are subject to FDA's user facility reporting requirements should follow the reporting procedures established by their facility. All other practitioners may submit these reports directly to MedWatch, FDA's voluntary reporting program. The reports can be submitted by phone at 800-FDA-1088, by fax at 800-FDA-0178, by internet at (under "How to Report", "Reporting by Health Professionals"), or by mail to: MedWatch, FDA, HF-2, 5600 Fishers Lane, Rockville, MD 20857.


Getting more information

All of FDA's medical device postmarket safety notifications can be found on the World Wide Web at Postmarket safety notifications can also be obtained through e-mail on the day they are released by subscribing to our list server. To subscribe, visit:  Additional information safety information is available at MedWatch.


Sincerely yours,

D. Bruce Burlington, M.D.
Center for Devices and Radiological Health
Food and Drug Administration



1. Wallden J, Gupta A, and Carlsen H-O. Supraventricular tachycardia induced by Datex patient monitoring system. Anesth Analg 1998; 86(6): 1339.

2. Chew EW, Trougher RH, Kuchar DL, and Thorburn CW. Inappropriate rate change in minute ventilation rate responsive pacemakers due to interference by cardiac monitors. PACE 1997; 20 (Part 1): 276-82.


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