HRS: With iPods, the Beat May Stumble

DENVER, May 11 -- The tunes pumped out by iPods may be off beat to patients with pacemakers, whose devices could be subjected to potentially dangerous interference, reported investigators here.
Among 83 patients with either single- or dual-chamber pacemakers, iPods placed on the chest caused over-sensing, telemetry interference, and, in one patient, pacemaker inhibition.
So reported Jay Thaker, a Michigan high school student, in collaboration with cardiologist Krit Jongnarangsin, M.D., and colleagues at Michigan State University and the University of Michigan, at the Heart Rhythm Society meeting.
"We found interference in 50% of patients," the investigators reported. "Our observations are disconcerting because implantable pacemakers have become commonplace worldwide and the iPod has become a ubiquitous personal digital entertainment device. Other mp3 players may also possibly interact with pacemakers."
iPods, and, presumably other types of MP3 players appear to produce electromagnetic fields that can interfere with pacemaker function, the authors said. Similar effects are known to occur when pacemakers are in proximity to theft-detection systems and airport metal detectors, according to the FDA.
The investigators conducted a prospective, single-blind study to evaluate potential interactions between iPods and pacemakers in 35 women and 48 men with a mean age of 76.1 + 8.6. Most (74) had dual-chamber devices, and nine had single-chamber devices.
The authors tested four different types of iPod (Apple brand) devices, including a hard-drive-based music player and photo, video, and "nano" models.
All devices were evaluated with pacemakers in both unipolar and bipolar configurations. The devices were tested in random order, and the technician who monitored ECG/pacemaker telemetry was blinded to both the pacemaker settings and the type of iPod test.
Both intrardiac electrograms and a surface ECG were monitored while the iPods were placed two inches away from the pacemaker for five to 10 seconds and were switched on and off.
The authors defined interference or interaction between the audio and heart devices as either:
Over sensing, defined as defined as spurious atrial/ventricular sensed events on the marker channel associated with atrial/ventricular inhibition, mode switching or high atrial/ventricular rates on rate histograms;
Telemetry interference, defined as any other interference that did not affect pacing function and was not detected by pacemaker interrogation; or
Pacemaker inhibition, defined as a failure to pace when pacing was expected.
They found that over sensing occurred in 20% of patients, telemetry interference occurred in 29%, and pacemaker inhibition occurred in 1.2% (one patient).
Both the over sensing and the telemetry interfere were persistent, occurring for more than 50% of the application time, and both events occurred more commonly with the hard-drive based music player (iPod 3G) and photo models, with the pacemakers in both unipolar and bipolar configurations.
None of the patients with interference reported experiencing symptoms, however, the investigators noted. They are reportedly investigating what constitutes a safe distance from pacemakers for iPod users.