Correspondence
Implantable Defibrillators, Pacemakers, and Electronic Antitheft Devices
N Engl J Med 1999; 340:1117-1119April 8, 1999
- Article
To the Editor:
The report by Santucci et al. (Nov. 5 issue)1 provides another example of sources of interference with implantable defibrillators.2 That this should occur is not surprising to anyone familiar with the sensing function of medical devices. Indeed, such systems have been falsely triggered by devices such as radio-controlled model cars and slot machines,3 electrocautery for unrelated surgery, and neural stimulators for pain control. Other devices and procedures that may be expected to inhibit the output of pacemakers or initiate inappropriate discharge of defibrillators include hair-removal (depilation) units and rapid-stimulation electromyography studies. In two patients with implantable cardioverter–defibrillators who were treated at my facility, the devices discharged while they were jump-starting a car with battery cables.
That such events may occur is not in question; up to 20 percent of all firings of implantable cardioverter–defibrillators are estimated to be inappropriate. However, readers should not interpret isolated case reports as representing a trend, and patients can take comfort in the infrequency with which such externally triggered events apparently occur. The reality is that several hundred thousand recipients of medical devices pass through electronic antitheft systems each day, yet there are but a handful of documented episodes of interference. Of the hundreds of thousands of Holter-monitoring studies performed each year, many in patients with implanted cardiac devices, the occurrence of such interference is all but unknown. Although it is easy to have discussions of who is responsible for minimizing such interactions (the electronic-field producer or the implanted-device producer),2 a simple technical solution is elusive. “Don't linger, don't lean” is an easy, practical remedy that was recently recommended by the Food and Drug Administration (FDA),4 and the American Heart Association has made similar recommendations.
In the same issue of the Journal, Drs. McIvor and Sridhar5 report on interactions between cardiac pacemakers and antishoplifting security systems. In Figure 1 of their report, the first two native QRS complexes suggest that the patient is in atrial flutter, which if sensed, can initiate pacing at the upper tracking rate of the device. The recorded rhythm strip is 18 seconds long, and, contrary to what is implied in the figure, it seems unlikely that the patient walked through the gate. An elderly person on crutches could navigate this space in half the time.
Each of us in the field of device therapy must take notice of such reports and strive to confirm the absence of any clinically significant consequences. The average patient, when passing through such a system, is exposed to the signal source for a period that is equivalent to one or two heartbeats, and little more than transient extra heartbeats or skipped beats have been demonstrated in response in prior studies.
The innovative therapies of cardiac pacing and defibrillator therapy have provided lifesaving benefits to hundreds of thousands of patients in the 40 years since the first pacemaker was installed. In the final analysis, all such patients can and should be encouraged to lead normal lives and to act with prudence during exposure to societal sources of electromagnetic interference.
5 ReferencesJ. Warren Harthorne, M.D.
Massachusetts General Hospital, Boston, MA 02114-26961
Santucci PA ,Haw J ,Trohman RG ,Pinski SL . Interference with an implantable defibrillator by an electronic antitheft-surveillance device. N Engl J Med 1998;339:1371-1374
Full Text | Web of Science | Medline2
Irnich W. Electromagnetic interference in current implantable devices. In: Vardas PE, ed. Cardiac arrhythmias, pacing & electrophysiology: the expert view. Dordrecht, the Netherlands: Kluwer Academic, 1998:427-36.
3
Madrid AH ,Moro C ,Martin J . Interference of the implantable defibrillators caused by slot machines. Pacing Clin Electrophysiol 1996;19:675-675 abstract.4
Important information on anti-theft and metal detector systems and pacemakers, ICDs, and spinal-cord stimulators. Rockville, Md.: Center for Devices and Radiological Health, September 28, 1998. (Or see: http://www.fda.gov/cdrh/safety/easnote.html.)
5
McIvor ME ,Sridhar S . Interactions between cardiac pacemakers and antishoplifting security systems. N Engl J Med 1998;339:1394-1395
Full Text | Web of Science | Medline
To the Editor:
We commend Santucci et al. for their discussion of the effects of electromagnetic interference on the activity of implantable cardioverter–defibrillators. However, we disagree with their assertion that clinical problems caused by electromagnetic interference with implantable defibrillators are rare and without life-threatening consequences. We are aware of cases in the literature and in our own experience in which electromagnetic interference in the perioperative environment has had potentially life-threatening ramifications.1,2
More than 500,000 patients in the United States have implantable cardioverter–defibrillators or pacer–cardioverter–defibrillators, and more than 40,000 are at risk for sudden death from malignant tachyarrhythmias. These devices are implanted in patients with severe, irreversible, structural heart disease with compromised myocardium. Many of these patients who are highly dependent on the proper functioning of the devices are exposed to electromagnetic interference in the perioperative environment.
Santucci et al. correctly point out that electromagnetic interference is rarely life threatening in most settings, but in the highly electromagnetic-interference–contaminated perioperative environment, patients may be at serious risk. Perioperatively, the sources of electromagnetic interference include surgical electrocautery, extracorporeal shock-wave lithotripsy, nuclear magnetic resonance imaging, high-voltage electrical devices, and radiotherapy for nondiagnostic purposes. Electromagnetic interference “noise” may have several undesirable consequences: inappropriate therapy, since electromagnetic interference may be identified as arrhythmia, stimulating dangerous tachyarrhythmias; changes in programming, since electromagnetic interference may be misinterpreted, altering algorithms for detection and treatment; and damage to circuitry, leads, or electrodes, rendering the device inoperable and causing permanent myocardial damage.3
All U.S. manufacturers of implantable cardioverter–defibrillators and pacer–cardioverter–defibrillators recommend that the devices be disabled (that antitachycardia and other functions be suspended) at a pacemaker clinic or by a technician if patients are to be exposed to electromagnetic interference perioperatively. Positioning a strong magnet over the pulse generator will temporarily suspend the automatic-detection and therapeutic capabilities of the device. Other suggestions include keeping a grounding pad 15 cm from the site of electromagnetic interference, orienting external defibrillator pads away from the pulse generator,4 avoiding diathermy in favor of bipolar cautery, careful monitoring of the pulse wave form and electrocardiogram, and remaining prepared to perform external conversion and cardiac resuscitation.5
Currently, despite the diversity and complexity of these devices, among the 10 U.S. manufacturers, there are no industry-wide guidelines for perioperative malfunction. To ensure the safety of patients, universal and practical solutions for perioperative management of implantable cardioverter–defibrillators and pacer–cardioverter–defibrillators should be developed by the appropriate clinical specialties in conjunction with the manufacturers.
5 ReferencesPaul Barach, M.D., M.P.H.
Massachusetts General Hospital, Boston, MA 02114Eric Baum, B.S., C.E.N.
University of Florida, Gainesville, FL 331861
Gaba DM ,Wyner J ,Fish KJ . Anesthesia and the automatic implantable cardioverter/defibrillator. Anesthesiology 1985;62:786-792
CrossRef | Web of Science | Medline2
Important information on anti-theft and metal detector systems and pacemakers, ICDs, and spinal-cord stimulators. Rockville, Md.: Center for Devices and Radiological Health, September 28, 1998. (Or see: http://www.fda.gov/cdrh/safety/easnote.html.)
3
Atlee JL. Cardiac pacing and electroversion. In: Kaplan JA, ed. Cardiac anesthesia. 4th ed. Philadelphia: W.B. Saunders, 1998.
4
Mirowski M ,Reid PR ,Watkins L ,Weisfeldt ML ,Mower MM . Clinical treatment of life-threatening ventricular arrhythmias with the automatic implantable defibrillator. Am Heart J 1981;102:265-270
CrossRef | Web of Science | Medline5
Mehta Y ,Swaminathan M ,Juneja R ,Saxena A ,Trehan N ,Atlee J . Noncardiac surgery and pacemaker cardioverter-defibrillator management. J Cardiothorac Vasc Anesth 1998;12:221-224
CrossRef | Web of Science | Medline
Author/Editor Response
The authors reply:
To the Editor: We agree with Dr. Harthorne that reports of inappropriate discharge of implantable cardioverter–defibrillators should not come as a surprise to anyone familiar with these devices. Although up to 20 percent of firings may be inappropriate, a very small percentage are caused by external electromagnetic interference. Clinically minor sequelae of electromagnetic interference in patients with pacemakers and implantable cardioverter–defibrillators have been described from a variety of sources. The intent of our report was to bring attention to the potential for such interactions to be serious and to alert patients, physicians, and the industry to the possibility of a severe interaction between implantable cardioverter–defibrillators and at least one type of electronic antitheft-surveillance unit. It was our impression that the potential seriousness of such interactions, although they are rare, was not known or widely anticipated and that patients were not routinely made aware of this phenomenon or informed of the simple method of prevention. Recently, Dr. Harthorne properly noted that no serious interactions had previously been documented between antishoplifting equipment and implantable cardioverter–defibrillators.1
Our recommendations were straightforward and in concordance with those of the FDA and American Heart Association. Specifically, the avoidance of prolonged exposure to antitheft equipment should minimize or eliminate problems. Since our report, several anecdotal reports of interactions between pacemakers and implantable cardioverter–defibrillators and antitheft equipment have been brought to our attention. Although it is not our intent to frighten patients unnecessarily, such interactions may not be as rare as previously thought, and we suspect they have been underreported. We believe that it is appropriate routinely to inform patients of the possibility of such an interaction and of the appropriate means to avoid it. This should be done in a reassuring manner, to avoid unnecessary psychological effects. It is only through a lack of awareness that more patients are likely to experience such events.
Dr. Barach and Mr. Baum correctly point out that electromagnetic interference in the hospital environment is a common cause of inappropriate functioning of pacemakers and implantable cardioverter–defibrillators. We have previously described common sources of electromagnetic interference in hospitals and the workplace.2,3 It is therefore preoperative routine in most institutions to take precautions such as those described to avoid undesirable effects, which can certainly otherwise be life threatening. Electromagnetic interference is a rare cause of serious interference during routine daily life. Fortunately, most of these interactions can be prevented by appropriate awareness and planning.
3 ReferencesPeter A. Santucci, M.D.
Sergio L. Pinski, M.D.
Richard G. Trohman, M.D.
Rush–Presbyterian–St. Luke's Medical Center, Chicago, IL 606121
Harthorne JW . Theft deterrent systems: a threat for medical device recipients or an industry cat fight? Pacing Clin Electrophysiol 1998;21:1845-1846
CrossRef | Web of Science | Medline2
Pinski SL ,Trohman RG . Implantable cardioverter-defibrillators: implications for the nonelectrophysiologist. Ann Intern Med 1995;122:770-777
Web of Science | Medline3
Pinski SL ,Trohman RG . More on patients with implantable cardioverter-defibrillators. Ann Intern Med 1995;123:893-893
Web of Science | Medline
Author/Editor Response
The myriad sources of electromagnetic radiation that can interfere with implanted medical devices have been recognized for quite some time.1 Our interest in electronic article surveillance systems, or antishoplifting gates, dates to the experience of one of our patients, who had an inappropriate discharge of her implantable cardioverter–defibrillator while standing next to such a system in a store.2 Our findings have since been confirmed.3,4 The largest formal test of implantable cardioverter–defibrillators, whose results were presented to the FDA in September 1998, suggested that 1 in 50 patients will have an inappropriate firing of their implantable cardioverter–defibrillator when exposed to the field of an acoustomagnetic electronic article surveillance system. Whether a 2 percent incidence of inappropriate firings is clinically significant depends on one's point of view. There is no need to cause a panic among the 98 percent who will not be affected, but by educating patients not to linger in these fields, we can eliminate the problem altogether. Because such systems can be concealed behind walls or under flooring, we would also be in favor of advisory signs alerting patients not to linger in areas near these systems.
In our study of patients with implanted pacemakers,5 virtually all interactions were confined to the strong, low-frequency, pulsed magnetic field generated by the acoustomagnetic type of system. Therefore, other types of systems may not need warning signs. We agree with Dr. Harthorne about the soundness of a “don't linger, don't lean” approach, since walking quickly through an acoustomagnetic electronic article surveillance gate (rather than pausing within or near the system) was associated with a large decrease in pacemaker interactions (from 96 percent to 16 percent). Most patients who are passing through such a system will not be actively using their pacing system at the time, so few will have symptoms, even if interactions occur. Others have a potential for interactions, some of which may cause symptoms. One type of pacemaker generator can even be reprogrammed by these systems, resulting in a faster base-line pacing rate.
It should now be accepted that interactions between such systems and implanted medical devices occur and are common in patients with pacemakers. What can be argued is whether enough patients are adversely affected to warrant concern. Our position is that the likelihood of clinical harm — even for the unlucky few who are at risk — can be virtually eliminated by proper education of patients.
5 ReferencesMichael E. McIvor, M.D.
Heart Institute of St. Petersburg, St. Petersburg, FL 33701S. Sridhar, M.D.
Affiliated Cardiologists, Phoenix, AZ 850041
Furman S ,Parker B ,Krauthamer J ,Escher DJ . The influence of electromagnetic environment on the performance of artificial cardiac pacemaker. Ann Thorac Surg 1968;6:90-95
CrossRef | Medline2
McIvor ME . Environmental electromagnetic interference from electronic article surveillance devices: interactions with an ICD. Pacing Clin Electrophysiol 1995;18:2229-2230
CrossRef | Web of Science | Medline3
Mathew P ,Lewis C ,Neglia J ,Krol RB ,Saksena S . Interaction between electronic article surveillance systems and implantable defibrillators: insights from a fourth generation ICD. Pacing Clin Electrophysiol 1997;20:2857-2859
CrossRef | Web of Science | Medline4
Santucci PA ,Haw J ,Trohman RG ,Pinski SL . Interference with an implantable defibrillator by an electronic antitheft-surveillance device. N Engl J Med 1998;339:1371-1374
Full Text | Web of Science | Medline5
McIvor ME ,Reddinger J ,Floden E ,Sheppard RC . Study of Pacemaker and Implantable Cardioverter Defibrillator Triggering by Electronic Article Surveillance Devices (SPICED TEAS). Pacing Clin Electrophysiol 1998;21:1847-1861
CrossRef | Web of Science | Medline
- Citing Articles (2)
Citing Articles
1
LUIS WAYAR, LLUIS MONT, ROSE M.F.L. SILVA, NELSON ALVARENGA, XAVI FOSCH, JESÚS CASTRO, JOSEP BRUGADA. (2003) Electrical Interference from an Abdominal Muscle Stimulator Unit on an Implantable Cardioverter Defibrillator:. Pacing and Clinical Electrophysiology 26:5, 1292-1293
CrossRef2
Michael Glikson, Paul A Friedman. (2001) The implantable cardioverter defibrillator. The Lancet 357:9262, 1107-1117
CrossRef
