MP3 player headphones placed within an inch of pacemakers or implantable defibrillators may interfere with the operation of the lifesaving cardiac devices, as study has found.(AFP/Getty Images/Scott Gries)AP - Have a pacemaker or an implanted defibrillator? Don’t keep your iPod earbuds in your shirt pocket or draped around your neck — even when they’re disconnected. A study finds that some headphones can interfere with heart devices if held very close to them.