Faulty Household Wiring Can Trigger a Heart Defibrillator

March 25 (HealthDay News) -- A literally shocking tale of the potential dangers of do-it-yourself home repairs for people with implanted defibrillators comes from cardiologists in Denmark.

"We recently cared for a patient who, after receiving an implantable cardioverter defibrillator, was readmitted shortly after hospital discharge because of two shocks delivered while the patient was showering," said a report in the March 26 issue of the New England Journal of Medicine.

There was no apparent physical reason why the device, which delivers a shock to restore normal heart rhythm if an arrhythmia occurs, should have gone off, but analysis "raised suspicion that electrical noise had caused an inappropriate ICD discharge," the report said. So the physicians sent an electrician to check the wiring of the house.

"It was found that it was due to improper installation of wiring in the patient's home because he installed a washing machine himself," said Dr. Kristian Eskesen, a cardiologist at Gentofte Hospital in Hellerup, one of the physicians reporting the event. "It was not properly grounded."

The shock would not have occurred if the washing machine had been installed by a licensed electrician, since Danish law requires safe grounding, Eskesen said. Cardiac safety was not the reason for the law, he said, "but it is one way of avoiding such problems with ICDs," he added.

There have been scattered reports of similar events with heart defibrillators. In 2002, for example, cardiologists in Hong Kong reported two such cases -- one caused by electrical signals from a power drill, the other by signals from a washing machine. And, German cardiologists described an instance of a defibrillator shock delivered because of electromagnetic signals from a washing machine.

"The reason for writing our report was to make colleagues aware of this possible problem," said report co-author Dr. Soren Hjortshoj, of Aalborg Hospital, in Aalborg, Denmark. "ICD therapy is generally a safe treatment that can help people with heart disease. But physicians should be aware of the possibility of false shocks and the reason for these."

In general, "manufacturers of ICDs do a tremendous job of making ICDs safe," Hjortshoj said. Still, "an ICD has to be sensitive to very small changes in the electrical impulses coming from the heart," which makes it vulnerable to some electrical signals originating outside of the heart, he said.

"It is luckily a rare phenomenon, but even in a very regulated society like Denmark, these occurrences take place," Hjortshoj said. "It is very essential that the ICD works correctly and triggers on the right event, otherwise it may be hostile."

Properly monitored, "the ICD is a safe treatment," he said. "But the authorities need to be aware that the regulations about electrical equipment should be followed."

SOURCES: Kristian Eskensen, M.D, cardiologist; Gentofte Hospital, Hellerup, Denmark; Soren Hjortshoj, M.D., staff specialist, Aalborg Hospital, Aalborg, Denmark; March 26, 2009, New England Journal of Medicine