Headphones May Cause Cardiac Device Malfunction
Because magnets inside portable headphones may cause malfunction, patients with implantable cardioverter-defibrillators (ICDs) or pacemakers should avoid placing the headphones from digital music players too close to their chests.
In a study of 100 patients with an implanted device, 30% had significant interference when certain models of headphones were placed within 2 centimeters or less from the skin surface of the chest. Problems included a disruption in the detection of tachyarrhythmia in cardioverter-defibrillators and asynchronous pacing in pacemakers. In one device, the equipment was permanently reprogrammed.
The FDA has previously concluded that the digital music player itself is not likely to cause electromagnetic interference, but there had not been studies performed on the accessory pieces, such as headphones.
Portable headphones typically contain neodymium magnets to create vibrations and sound waves.
The study was performed by Dr. William Maisel MD MPH of Beth Israel Deaconess Medical Center and reported in the October issue of Heart Rhythm.
Researchers evaluated the magnetic fields associated with eight different models of headphones. Two clip on (over the ear) headphones and 6 ear bud (inside the ear) headphones were placed over a Gauss meter that measure electromagnetic fields. All eight models exceeded 10 Gauss, which is considered sufficient to close the read switch and disable sensing in the implanted cardiac device. Five models had levels over 200 Gauss.
As the headphones were moved away from the device, the field strength decreased for all of the ear bud models, but the two clip-on versions continued to register above 10 Gauss. The model numbers were Sony MDR-Q22LP and Phillips SBC HS430. The magnetic fields were the same whether or not they were plugged into the digital music player or whether or not the player was turned on.
The model that produced the least amount of magnetic field strength was the JVC HA-FX33A in-ear model at 11 Gauss when placed directly over the meter.
For patients that have implanted cardiac devices, it is recommended that patients avoid placing any electronic equipment directly over their devices and that portable headphones be placed at least 3 centimeters – 1.2 inches – from the chest.
Source reference: Lee S, et al "Clinically significant magnetic interference of implanted cardiac devices by portable headphones" Heart Rhythm 2009; 6: 1432-36.