Study investigates internal defibrillators and appropriate shocks

17th August 2015

A study has been looking at how many people with internal defibrillators have appropriate shocks from their devices.

The technology, termed implantable cardioverter defibrillators or ICDs, are given to people who have survived a cardiac arrest or are thought to be at risk of having one.  The pacemaker like devices are given to people with a range of heart problems, including some with cardiomyopathy, and if they develop a dangerous heart rhythm the devices can shock their hearts back into a normal rhythm.

The researchers, led by Dr Avi Sabbaq from the heart centre at the Chaim Sheba Medical Centre in Tel Aviv, Israel, said there was limited data on how many shocks the devices gave to people in real life settings.


So they investigated the rate of appropriate life-saving ICD shock therapies in people on the Israeli ICD Registry, which included all implants and other ICD procedures done nationally. They looked at 2,349 people who were enrolled in the registry and followed them up for survival, hospital admissions and ICD therapies since 2010.

Appropriate ICD shocks among patients who received an ICD because they were thought to be at risk of a dangerous rhythm was 1.1 per cent after a year and 2.6 per cent at 30 months.  The figures for those who had already had a cardiac arrest were 3.8% at 1-year and 7.4% at 30 months. A total of 253 (4.8%) patients died during follow-up, but 65% were due to non-cardiac causes.

The researchers reported that the rates of life-saving appropriate ICD shocks in patients fitted with the devices for prevention were lower than previously reported in a contemporary real world setting.
They said the findings suggested a need for improved risk analysis and patient selection for the devices.

Some ICDs also include biventricular pacemakers to help the heart beat more in unison and improve symptoms.