According to a laboratory study presented on 5 May 2011 at Heart Rhythm 2011, the Heart Rhythm Society’s 32nd Annual Scientific Sessions, the distance at which headphones cause magnetic interference with active implanted cardiac medical devices (AICMDs), such as implantable cardiac pacemakers (ICPs) and cardioverter defibrillators (ICDs), is less than previously reported.
Headphones and earbuds do not cause magnetic interference with AICMDs at a distance of two centimetres or more. Earlier studies have raised concerns about potential effects of interference from headphones used with personal music players at a distance of three centimetres.
The laboratory study used a human torso simulator consisting of a plastic box filled with 0.18% saline solution. Simulated ECG signals were used to inhibit the pacing activity of 29 AICMDs (21 ICPs and 8 ICDs). Separation distances up to 30cm from the AICMDs were tested on a total of 21 different models of headphones. Tests were repeated with each type of headphone in direct surface contact with AICMDs with malfunctions noted.
Study results show no interference observed from any of the 21 headphones and earbuds at a distance of two centimetres or more from the surface of the AICMDs, and no specific type of headphone or earbud changed any of the parameter settings or affected the functionality of the devices. The measured static magnetic flux densities (B) of the headphones or earbuds were 11.8mT or less at the surface of the device, and 0.4mT or less at a distance of two centimetres.
“Based on the study results, the risk of interference on AICMDs is truly dependent on how close the patient is to the device and the risk becomes minute as the distance becomes greater,” stated Kok-Swang Tan, Medical Devices Bureau, Therapeutic Products Directorate, Health Canada. “Although the risk is low, it is critical for individuals to avoid hanging headphones around their neck or storing them inside a front pocket, and someone who is wearing headphones should never rest their head on the chest of someone who has any type of cardiac device.”
Previous research by Sinjin Lee et al, published in the October 2009 edition of HeartRhythm, cited a clinically significant impact of magnetic interference on the function of AICMDs at distances less than three centimetres. However, the laboratory study conducted by Kok-Swang Tan at two centimetres proved no interference from any of the headphones or earbuds tested. The differentiating factor is the distance from which the headphones or earbuds can or will cause interference with AICMDs. Patients should be advised to keep headphones or earbuds at least two centimetres from their device to avoid any potential damage.