SNOWMASS, COLO. — The everyday 21st century electronic communications environment poses unprecedented electromagnetic interference hazards for patients with pacemakers or implantable cardioverter-defibrillators, Dr. William H. Spencer III cautioned at a conference sponsored by the Society for Cardiovascular Angiography and Interventions.
“What are you going to tell your patients in 2006 regarding smart phones and other wireless communication devices such as PDAs, wireless computers, and iPods? Can they use them, and how should they use them?” asked Dr. Spencer, professor of medicine at the Medical University of South Carolina, Charleston.
Pacemakers can respond to electromagnetic interference (EMI) in a plethora of unwelcome ways: complete inhibition of pacing, asynchronous pacing, rapid pacing, mode reset to a very safe pacing mode, or physical damage to the generator and/or pacing leads. Implantable cardioverter-defibrillators (ICDs) may deliver an inappropriate shock or antitachycardia therapy or, worse, be inhibited from delivering therapy when needed. Device memory corruption can occur, making it impossible for physicians to reconstruct what happened when EMI was encountered.
The important thing to know about EMI due to wireless communication devices is the 10-cm rule. All implanted cardiac devices now incorporate internal filters that are highly effective in rejecting all but the strongest electromagnetic signals—those originating within about 10 cm of the device or leads. For this reason patients shouldn't carry their cell phone in a shirt or breast pocket. Patients are also supposed to hold the phone to the ear farthest from the device, which is typically the right ear.
Walk-through metal detectors used in airport screening are safe provided the patient moves briskly through. Heart devices contain very little ferromagnetic material and shouldn't trip the alarm. But if the alarm does go off, under no circumstances should the patient submit to a search using a hand-held wand over the chest; far better to be thoroughly searched by hand.
Electronic article surveillance systems used in stores to prevent shoplifting can also cause problems. “The patient should be instructed to walk rapidly through the gate and do not tarry,” said Dr. Spencer, who holds stock in Medtronic and Boston Scientific.