S-ICDs can be as effective as traditional internal defibrillators, says new study

8th December 2016

An internal defibrillator (ICD) that does not have leads into the heart has shown itself to be an effective treatment for those who have already experienced a dangerous heart rhythm and those thought to be at risk of having one.

That is the result of an international study involving doctors in the UK, Netherlands, Czech Republic and America.

Subcutaneous ICDs (or S-ICD) are an alternative to the more traditional implantable cardioverter defibrillators (ICDs).

ICDs can detect a life-threatening heart rhythm and give a shock to restore normal heart rhythm. But unlike traditional ICDs, S-ICDs cannot also pace the heart. So they are not suitable for people who have significant heart failure or need a pacemaker. Because the leads are outside the heart, complications that can occur with ICD leads are reduced.

The researchers said the S-ICD had also not been well studied in the most commonly treated ICD patient population – those with some heart pumping problems and thought to be at risk of a cardiac arrest.

The researchers looked at 856 people with an S-ICD, first comparing 600 patients thought to be at risk with 253 others who had already experienced a dangerous rhythm.  They looked at those thought to be at risk, including 379 with an ejection fraction or EF (a measure of how well the heart is pumping) of or below 35% compared 149 people with an EF greater than 35%.

The researchers said they saw no differences in mortality, complications, inappropriate or appropriate therapy between those with the device who had had a dangerous rhythm and those thought to be at risk.

However, those who had already experienced a dangerous rhythm had a higher incidence of appropriate therapy. In those thought to be at risk, those with an EF of 35% or less were significantly older patients with more other health problems and had higher mortality (3% annually versus 0%). Despite these differences, device complications, shocks, and incidence of inappropriate shocks were not significantly different to those with an EF over 35 per cent.

The researchers concluded that S-ICDs performed well in protecting people from sudden cardiac death and in the group fitted with the S-ICD as a precaution, device performance was independent of EF.

For more details, see here