Pacemaker Interference
Pacemaker Interference
Abstract & Commentary
By John P. DiMarco, MD, PhD, Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville. Dr. DiMarco is a consultant for Novartis, and does research for Medtronic and Guidant.
Source: Lee S, et al. Clinically significant magnetic interference of implanted cardiac devices by portable headphones. Heart Rhythm. 2009;6:1432-1436.
Portable music players are now widely used at all age levels. The headphones used with these players, both ear-bud and clip-on varieties, are frequently worn in such a way that they may come into close proximity to a pacemaker or ICD in patients with these rhythm-management devices. In this paper, Lee et al report on the potential for magnetic interference associated with headphone use. Eight different headphone models, two clip-on types and six in-ear models, were tested. Two different MP3 players (iPod Nano and iPod Shuffle) were also analyzed. Patients were monitored by single-lead ECG monitoring during the testing. After exposure to the earphones and MP3 players, the devices were re-interrogated to verify normal function. The headphones were placed on the patient's chest in nine prespecified locations. The effects of headphone and player exposure were tested both during 100% pacing and during demand-single or dual-chamber demand pacing. Device interactions were classified as follows: 1) pacemaker magnet response with delivery of asynchronous pacing; 2) ICD magnet response resulting in an audible tone from the ICD magnet alarm with suspension of detection; 3) oversensing with delay or inhibition of scheduled paced beats during continuous pacing; 4) undersensing with failure of the device to detect intrinsic cardiac signals and; 5) device reprogramming. In vitro testing of each device was performed using a DC gaussmeter to measure field strengths at 0, 1, 2, and 3 cm from the headphone.
There were 100 patients in the study. Devices from the three major manufacturers (Boston Scientific-Guidant, Medtronic, and St. Jude Medical), including 20 different models, were tested. In vitro testing revealed that the greatest magnetic field strength occurred right at the surface of the headphone. At a distance of 0 cm, five of the eight units tested had a magnetic-field strength of over 200 gauss. At a distance of 2 cm, two of the units tested had a magnetic-field strength ≥ 10 gauss. The two clip-on headphones tested had higher field strengths than the ear models. Clinically significant magnetic interference was caused by the headphones in 30 of 100 patients. All the significant interactions were seen with the two clip-on headphone devices, which had higher magnetic-field strengths. The most common type of interaction was a magnet response with either asynchronous pacing by pacemakers or inhibition of tachycardia detection by ICDs. Removal of the headphones from the patient's chest immediately restored the device to normal function, except in one patient who experienced device reprogramming from a DDD to DOO mode. No headphone tested produced clinically significant interference when the headphone was 3 cm or more from the skin's surface. The two MP3 players tested did not cause magnet responses, oversensing, or undersensing.
Lee et al conclude that portable headphones commonly used in personal electronic devices can cause clinically significant interference when placed in close proximity to implanted pacemakers and ICDs. They advise that patients should be cautioned to keep headphones at least 3 cm away from their device.
Commentary
Headphones used with personal electronic devices contain magnets in the headphones. The most common magnetic substance used is neodymium. The small neodymium magnets in headphones constantly generate a magnetic field whether or not the headphone is connected to a device that is powered on. In this paper, we see that careless use of headphones has some potential to cause interference with pacemakers or defibrillators if the headphone is worn or carried in close proximity to the implanted pacemaker or ICD. This paper shows that the field strength with various headphone models is variable and there is no way for an individual patient to test his own headphones. Therefore, the caution about how headphones should be carried or worn must apply to all models that patients might use. However, the limited data shown here suggest that patients should also be advised that clip-on models carry the greatest potential risk.
Portable music players are now widely used at all age levels. The headphones used with these players, both ear-bud and clip-on varieties, are frequently worn in such a way that they may come into close proximity to a pacemaker or ICD in patients with these rhythm-management devices.Subscribe Now for Access
You have reached your article limit for the month. We hope you found our articles both enjoyable and insightful. For information on new subscriptions, product trials, alternative billing arrangements or group and site discounts please call 800-688-2421. We look forward to having you as a long-term member of the Relias Media community.