Digital Cellular Phone Interference with Cardiac Pacemakers

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Contact: MDB Enquiries

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I.L. No. 108 November 6, 1995

To: Hospital Administrators Pacemaker Implant Centres and Clinics

Attention: Cardiologists

Subject: Digital Cellular Phone Interference with Cardiac Pacemakers

Research conducted by Health Protection Branch laboratories has confirmed reports that electromagnetic interference (EMI) from nearby digital cellular phones may affect the operation of some implanted cardiac pacemakers. It must be emphasized that these effects have been seen only with the new digital cellular phones now being introduced in North America; there have been no reports of interference from analog cellular phones which have been in use for a number of years. Most cellular phones used in Canada are analog. However, digital cellular phones are increasing in popularity.

Preliminary reports from the Mayo Clinic in Rochester, Minnesota1, and the Mount Sinai Medical Center in Miami Beach, Florida2, indicated that digital cellular phones could produce the following types of EMI effects:

• inhibition of ventricular output,
• asynchronous pacing,
• atrial channel tracking of electromagnetic noise, and
• safety pacing (unwanted but non-hazardous pacing).

Interference occurred only when the phones were placed in very close proximity to the pacemakers (in most cases, within 8 cm).

The Health Protection Branch has not received reports of similar incidents in Canada. However, the Branch has conducted laboratory studies of fourteen pacemakers (nine single chamber and five dual-chamber types) to investigate this concern. The studies have provided the following information:

• Of the fourteen pacemaker models tested by the Branch, one single chamber model and two dual-chamber models were found to be susceptible to EMI from digital cellular phones. The operation of a digital cellular phone decreased the frequency of the single chamber model's output pulses and decreased the ventricular pacing rate of one brand of dual chamber pacemaker. This could be hazardous to patients who are fully dependent on the pacemaker. In the case of the second dual-chamber model, when the output of the pacemaker was inhibited by an external electrocardiogram signal, the operation of the phone induced rhythmic pacing. This unwanted pacing could compete with the normal sinus rhythm to induce tachycardia or fibrillation. The digital cellular phone also induced unwanted pacing, at a lower rate, in the other brand of dual chamber pacemaker when the pacemaker was inhibited by the external electrocardiogram signals. However, this unwanted pacing, at the lower rate, was synchronous with the external electrocardiogram signals.
• The EMI occurred only while a call was in progress. When the phone was turned off, the interference stopped and the pacemaker resumed its normal operation.
• EMI does not appear to occur if the digital cellular phone is more than 4.5 cm from the pacemaker. This suggests that the pacemaker will not be affected when the phone is used in the normal talking position, but could be affected if the phone is carried in the breast pocket of a shirt or coat.
• An analog cellular phone used in the tests did not produce EMI with these pacemakers.

The Health Protection Branch has discussed this issue with all major manufacturers of pacemakers sold in Canada. The manufacturers intend to revise the labelling of their products and are studying long-term solutions for improving the EMI immunity of their pacemakers.

The chances that EMI from digital cellular phones will result in a life-threatening situation are low. Nevertheless, surgeons who implant cardiac pacemakers should inform their patients to take the following simple precautions with digital cellular phones:

• Be aware that the use of a digital cellular phone very close to the pacemaker may cause the pacemaker to malfunction.
• When using a digital cellular phone, hold it to the ear opposite the side of the body where the pacemaker is implanted.
• When the phone is not in use, do not place it closer than 5 cm to a pacemaker because an incoming call will switch the phone to its transmission mode and may cause interference. For example, avoid carrying the cellular phone in a shirt or jacket pocket directly over the pacemaker.

Inquiries concerning this hazard and reports of incidents should be addressed to the Director, Medical Devices Bureau, Environmental Health Directorate, Health Protection Branch, Tunney's Pasture, Postal Locator 0301H1, Ottawa, Ontario, K1A 0L2. Telephone: (613) 952-7125, Fax: (613) 957-7318. Medical device problems may also be reported through the toll free Medical Devices Hotline at 1-800-267-9675.

Kent R. Foster
Assistant Deputy Minister

References:

• Hayes DL, VonFeldt L, Neubauer S, Christiansen J, Rasmussen MJ. Effect of digital cellular phones on permanent pacemakers. PACE. 1995;18:863 (NASPE Abstracts)
• Carrillo R, Saunkeah B, Pickels M, Traad E, Wyatt C, Williams D. Preliminary observations on cellular telephones and pacemakers. PACE. 1995;18:863 (NASPE Abstracts)

^© Minister of Supply and Services Canada, 1995