Electromagnetic Interference in Implantable Rhythm
Devices - The Indian Scenario
Johnson Francis, MD, DM.
Associate Professor of Cardiology,
Medical College Calicut, Kerala, India.
Address for correspondence: Dr.
Johnson Francis, "Pulikkottil", Thondayad, P.O. Chevarambalam, Calicut
-673017, Kerala, India. Email: johnsonf@vsnl.com
Implantable rhythm device (IRD) is the generic
name for the group of implantable devices used for diagnosis and
treatment of cardiac arrhythmias. Devices in this category include
cardiac pacemakers, implantable cardioverter defibrillators and
implantable loop recorders. Since these devices have complex
microelectronic circuitry and use electromagnetic waves for
communication, they are susceptible to interference from extraneous
sources of electromagnetic radiation and magnetic energy.
Electromagnetic interference (EMI) is generally not a major problem
outside of the hospital environment. The most important interactions
occur when a patient is subjected to medical procedures such as
magnetic resonance imaging (MRI), electrocautery and radiation therapy.
Two articles in this issue of the journal discusses various aspects
of EMI on IRD1,2 .
Together these articles provide a good review of the various sources of
EMI and their interaction with IRD for the treating physician.
Prof. Seymour Furman has given an excellent suggestion during his
editorial preview of these articles. He has called upon the Indian
investigators to assess the situation in the local community. Shree
Pacetronix Ltd., the only Indian manufacturer of pacemakers, has
informed that no case of EMI has been reported in their pacemakers,
though a well designed study to test this aspect has not been conducted
so far. They also mention that their pacemakers incorporate EMI
protection. Largest number of devices implanted in the country are from
Medtronic Inc. They have not received reports of EMI from India. It is
likely that most or all instances of EMI may have gone unreported.
Cell phones are fast becoming the common man's commodity in Indian
cities and it is likely to be the single most common source for EMI.
Cell phone operators in India follow the European standards of GSM
(Global System Mobile) cellular telephony. D-net (900 MHz,
digital pulsed) and the E-net (1,800 MHz, digital pulsed) are being
used by operators in the country. C-net (450 MHz, analogue) which was
being used in European countries, is not being used by any of the major
operators in the country. An IRD is
most vulnerable to EMI during interrogation and programming. It is not
advisable to have an activated cell phone in the vicinity during this
process. Pacemaker patients really suffering from EMI due to mobile
phones are very rare unless the phone is positioned in the pocket
just over the pulse generator. The contralateral pocket or the belt
position of the mobile phone guarantees undisturbed operation of the
pacemaker in most patients. A risk analysis reveals that the portion of
patients really suffering from EMI due to
mobile phones is about 1 out of 100,0003.
As Prof. Furman suggests, keep a cell phone in the opposite hand and
ear
from the implanted device and enjoy life.
MRI is an important diagnostic modality in various disciplines of
medicine. A number of patients are put through MRI for orthopedic
purposes without recognition of their IRD. In general, MRI is
contraindicated for a patient with an IRD; but recent studies have
shown that MRI using 0.5 Tesla is unlikely to produce irreversible
changes in the pacemaker4. If a patient
with an IRD badly needs an MRI, it would be worthwhile to check up
whether the local system is operating at 0.5 Tesla or above. Higher
magnetic fields give faster acquisition of
images, but are more likely to interfere with the function of the IRD.
Systems working at 0.5 Tesla are available in the country so that it
may be considered in such situations. Interrogating and reprogramming
the IRD before and after an unavoidable MRI is mandatory.
According to a press report which appeared in February 2002, Wilson
Greatbatch, pacemaker pioneer, was planning to build an MRI-proof
pacemaker with fiber optic leads and low-power semiconductor laser5. If his efforts bear fruit, in future we may be
able to subject patients with an implanted pacemaker to MRI without any
hesitation.
Radiation therapy with the IRD in the radiation field is likely to
destroy the device by damaging the very sensitive CMOS (Complementary
Metal Oxide Semiconductor) circuitry. In case of dire necessity, it is
advisable to explant the pacemaker and reimplant it in a different
location. Patients with IRD are advised not to linger within weapons
detectors or theft detectors. The potential for exposure to such
devices are rapidly on the
increase in our country due to various reasons.
An increasing number of pacemaker-bearing individuals are being
transported by air. Although modern pacemakers are effectively shielded
from electromagnetic interference (EMI), the magnitude of
electromagnetic radiation in cockpits of general aviation aircraft is
higher and of a different nature than experienced in daily life. A
recent study showed that modern pacemakers are unaffected by EMI in the
cockpit environment of single-engine fixed-wing aircraft.6
In conclusion, most patients with IRD can lead a near normal life with
certain precautions to avoid EMI. It is important that the treating
physician be aware of the potential sources of EMI to which each
particular individual is likely to be exposed and choose the type of
device and site of implant accordingly.
References
1. Okan Erdogan.
Electromagnetic Interference on Pacemakers. Indian Pacing and
Electrophysiology Journal 2002; 2(3):3. [Free Full Text]
2. Marcos
de Sousa, Gunnar Klein, Thomas Korte, Michael Niehaus. Electromagnetic
Interference in Patients with Implanted Cardioverter-Defibrillators and
Implantable Loop Recorders. Indian Pacing and Electrophysiology Journal
2002; 2(3):4. [Free Full
Text]
3.
Irnich W, Batz L, Muller R, Tobisch R. PElectromagnetic interference of
pacemakers by mobile phones. PACE 1996; 19:1431-46
4.
Vahlhaus C,
Sommer T, Lewalter T, Schimpf R, Schumacher B, Jung W, Luderitz B..
Interference with cardiac pacemakers by magnetic resonance imaging: are
there irreversible changes at 0.5 Tesla?. Pacing Clin Electrophysiol
2001; 24:489-95.
5.
Heart Wire -Mediapulse from the heart.org newsletter Feb 22, 2002,
quoting Dow Jones Newswire story appearing in the Wall
Street Journal, New York.
6.
De R, Van D. Electromagnetic interference in pacemakers in
single-engine fixed-wing aircraft: a European perspective. Aviat Space
Environ Med 2002; 73:179-83
