Implantable cardioverter-defibrillators (ICDs), which are designed to stop dangerous heart rhythms, can produce inappropriate shocks, thereby increasing the risk of mortality, according to researchers at Leiden University Medical Center.

To study the risks associated with ICDs, the researchers analysed more than 1500 patients who had an ICD implanted at their medical centre between 1996 and 2006.

The study results showed that at least 13% of the patients experienced on inappropriate shock from the ICD over a period of 3.5 years on average.

The risk of the patient experiencing inappropriate shocks increased from 7% in the first year to 18% after five years.

In addition, one inappropriate shock was associated with 60% increase in the risk of patient’s death, and with five inappropriate shocks, the risk increased by four-fold.