Research at Harvard University shows “that pacemakers and implantable cardioverter defibrillators (ICDs) may react negatively to the magnets inside MP3-player headphones”. As per the researcher’s report, pacemakers and ICDs must be at least 1.2 inches away from the headphones. But why ? This is because the small magnets inside the headphones are powerful enough to send false signals to the heart, which may result in skipped heart beats for pacemakers. Its even worse for ICDs, which may even shutdown !

[source: pcworld.com, nhlbi.nih.gov]