A 'phone call to heaven. Is the cellular 'phone ... and digital mobile telephones interfere with the ... The limitations of this first study were the small sample size ...
European Heart Journal (1997) 18, 1528-1529
A 'phone call to heaven. Is the cellular 'phone dangerous for its user with a pacemaker? See page 1632 for the article to which this Editorial refers
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In this issue Altamura et a/.'1' describe how analogue and digital mobile telephones interfere with the normal function of artificial cardiac pacemakers. We know caution is necessary with electrocautery, electroshocks, electrical nerve stimulation, and radiofrequency ablation if a patient has a pacemaker (or a defibrillator)'2'. In the general environment only powerful industrial sources of electromagnetic signals (such as a radar installation or welding machines) are able to damage a device or its owner'31. However, our rapidly changing environment now provides many more possible sources of interference: leaky microwave ovens, anti-theft devices all have been shown to cause short-lasting pacemaker dysfunction'4'. This usually causes reversion to an interference mode that protects the patient from asystole. This asynchronous pacing might be arrhythmogenic and may even provoke ventricular fibrillation'51. Other minor problems are interference with sensor function, and reversion of sophisticated softwaredriven pacing to basic ventricular pacing. This might cause disturbing symptoms (asynchrony between atria and ventricles, or fast pacing), but is not usually dangerous. The booming mobile 'phone industry introduces a new environmental threat to our patients. With the growth of this market in Europe the mobile 'phone is now ubiquitous. In some countries, analogue devices were widely available before the digital Global System for Mobile Service Network (GSM) spread through the rest of Europe. In-vitro studies from biomedica! engineers have shown that the mobile 'phone can cause pacemaker dysfunction. The electrode acts as an antenna, and the pacemaker picks up the signal'6'. Physics and mathematics can help us understand how a particular 'phone with a given output needs to be kept at a given distance from the pacemaker site, to avoid interference. Both the pulsed 900 MHz radiofrequency signal of a GSM, or the magnet in the cellular 'phone can disturb normal pacemaker function, provoking inhibition of the output, or synchronous ventricular pacing. Tracking of the signal to the programmed upper limit is another possibility'7'. Systematic in-vivo investigations, relevant for the daily situation (as many competing standards coexist today) remain scarce. Nevertheless, modern
hand-held digital mobile 'phones (GSM) have been assessed in patients with DDD, VDD and VVI systems in various conditions and sensitivity settings'8'. It appears that electromagnetic interference occurs most often when the 'phone is close to the pectoral site of device implantation, and more frequently when the device is programmed to a high sensitivity, or when the lead is unipolar. Inhibition is very uncommon in bipolar modes, and at nominal sensitivity in unipolar modes (0% and less than 2-5% respectively). The limitations of this first study were the small sample size, and the limited number of devices (only four pacemakers and four GSM brands were tested). More systematic studies remain necessary in order to prepare correct guidelines for the future. The present study involves a wider range of companies and pacemakers, with different software and hardware, and seem to be representative of the European market. The limitations are that only one GSM, and one analogue device were used. All pacemakers had unipolar leads (which still reflects the real situation in a majority of patients) and most have pacemakers of high sensitivity. This means that the higher number of devices affected by electromagnetic interference (20% by GSM) is very acceptable. However, permanent program alteration or pacemaker circuit damage was not observed. What measures have to be taken? The cardiologist responsible for a pacemaker clinic will have to consider using bipolar pacing, as less interference will be observed. Careful implantation, ensuring that nominal sensitivity or even low sensitivities can be programmed, is a rule. When atrial sensing or rateresponsive devices are used, low upper rates must be programmed for GSM users. Given the existing evidence, patient advice should encompass a mediocolegal point of view. The patient should be told that it can be assumed that a 'phone carried at a site contralateral to a pacemaker or an ICD, or held at the contralateral ear will not interfere with normal device activity. However, if his life is dependent on continuous, normal ventricular pacing, even short interference with device function can be dangerous. Transtelephonic transmission of pacemaker data by a mobile 'phone is unthinkable, while this becomes more and more attractive with the modern telecommunication possibilities and budgetary restrictions . . . Device companies have important responsibilities. They should consider protective shielding, as
Editorials
reported here. In the mean time, we must switch off our mobile 'phones while in hospitals, and in every decent restaurant . . . L. J. JORDAENS University Hospital, Ghent, Belgium
References [1] Altamura G, Toscano S, Gentilucci G et al. Influence of digital and cellular telephones on implanted pacemakers. Eur Heart J 1997; 18: 1632-1641. [2] Cazeau S, Theret D, Lascault G. Gougne G, Ritter P, Ripart A. Environment et stimulation cardiaque definitive. Arch Mai Coeur Vaiss 1992:85: 77-81. [3] Marco D, Eisinger G, Hayes DL. Testing of work environments for electromagnetic interference. PACE 1992: 15: 201622. [4] Dodinot B, Godenir JP, Costa AB. Electronic article surveillance: a possible danger for pacemaker patients. PACE 1993; 16- 46-53. [5] Billitch M, Cosny RS, Cafferky EA. Ventricular fibrillation and competitive pacing. N Engl J Med 1967; 276: 598-604. [6] Irnich W, Batz L, Muller R, Tobisch R. Storbeeinflussing von Herzschnttmachern durch Mobilfunkgerate. Herzschrittmacher 1995; 15: 5-49. [7] Barbaro V, Bartolini P, Donato A et al. Do European GSM mobile cellular phones pose a potential risk to pacemaker patients? PACE 1995, 18: 1218-24. [8] Naegeli B, Osswald S, Deola M, Burkart F. Intermittent pacemaker dysfunction caused by digital mobile telephones. J Am Coll Cardiol 1996; 27: 1471-7.
Eur Heart J, Vol. 18, October 1997
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has been realized in other sectors of the biomedical industry. In the mean time, manuals should mention the possibility of interference. Consideration should also be given to the manufacture of filter techniques designed to protect circuitry from electromagnetic interference. This can only be done in coordination with those responsible for the interference source (i.e. the telecommunication giants). It seems unreasonable for the biomedical industry alone to take responsibility for this important issue, when the know-how for protective shielding is also vital in other fields. The manual of a very common mobile 'phone states that a GSM can interfere with aeroplanes, fuel stations, industrial chemical installations, hearing devices, radios, televisions and personal computers (not to mention that its magnet can wipe out data on floppy disks and credit cards). It is unreasonable for hospitals to forbid the use of GSMs while using diathermy, personal beepers, pocket 'phones and radiophones. Nevertheless, as can be seen, there is some justification behind this warning, and we can only hope that those responsible for the electromagnetic pollution of the environment take their responsibility seriously. Whether the European safety standards are sufficient today is not clear. They should continuously be adapted to incorporate new information, such as that
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