THURSDAY, March 27 (HealthDay News) -- A new study says that iPods and other digital music players don't affect pacemaker function, a finding that contradicts a study published last year.

That May 2007 study concluded that errant electronic noise from iPods could cause malfunctions in implantable cardiac pacemakers. But cardiac electrophysiologists at Children's Hospital Boston were surprised by that finding, mostly because many of their young patients with pacemakers use digital music players and have never had problems.

"But kids and parents bring up this concern all the time, prompting us to do our own study," study senior investigator Dr. Charles Berul, director of the pacemaker service at the hospital, said in a prepared statement.

A team at the hospital ran tests on 51 patients who came in for appointments. Their average age was 22 years, and they all had active pacemakers or implantable cardioverter-defibrillators (ICDs). The researchers played four different kinds of digital music players (two kinds of iPods, a SanDisk Sansa and a Microsoft Zune) directly over the each patient's pacemaker or ICD.

The music players caused no interference with the devices' functioning -- electrocardiographic (EKG) recordings showed no changes in any of the 255 separate tests and none of the patients showed any symptoms.

"This provides reassuring evidence that should allay the fears of people using iPods and other digital music players," Berul said.

However, this study did find that in 41 percent of patients, the music players interfered with communications between the programmer and the pacemaker or ICD. The programmer is a computerized device used by doctors to check and recalibrate the heart devices. This indicates that patients shouldn't use digital music devices while a doctor is reprogramming their heart device, the researchers said.

The study appears in the April issue of Heart Rhythm.

An editorial in the same issue of the journal suggests that this study and the May 2007 study may have reached conflicting conclusions due to different testing methods and interpretation of pacemaker recordings. Also, the earlier study involved patients whose average age was 77.

More information

The U.S. Food and Drug Administration has more about pacemakers.