FAQ

No, not in the conventional sense. This is the most clinically important difference between an S-ICD and a standard transvenous ICD.

An S-ICD can deliver brief post-shock pacing — a short burst of pacing in the seconds immediately after it has delivered a defibrillation shock, to prevent the heart pausing dangerously in that window. But it cannot provide ongoing bradycardia pacing (pacing that keeps the heart from beating too slowly on a continuous basis) or anti-tachycardia pacing (ATP, which is rapid pacing used to interrupt a fast heart rhythm before it needs a shock).

This means an S-ICD is not appropriate if:

• You have a slow heart rate that requires a pacemaker to maintain an adequate rate
• You have a type of fast heart rhythm that can be reliably terminated with ATP, which is less painful than a full shock

Some patients who need both ICD protection and pacing have an S-ICD combined with a separate leadless pacemaker (such as the Micra device), which sits inside the right ventricle and handles pacing without transvenous leads. This combination is used in selected cases where both subcutaneous defibrillation and pacing are needed but traditional transvenous leads are undesirable. Your electrophysiologist will determine which configuration is right for you.

Category: Implantable Devices

An S-ICD is considered when someone needs ICD protection against life-threatening arrhythmias but does not currently require ongoing pacing therapy. It tends to be particularly well suited to:

• Younger patients, where avoiding transvenous leads reduces lifetime exposure to the complications those leads can cause over decades of use, including fracture, infection, and the need for lead extraction procedures
• People with congenital heart disease or unusual cardiac anatomy, where placing transvenous leads is technically difficult or carries higher risk
• Patients at elevated risk of device infection, where keeping leads out of the bloodstream reduces the chance of serious endovascular infection
• People who have already experienced transvenous lead complications, such as lead fracture or infection, and need a different approach

Before an S-ICD can be implanted, a sensing screening test is carried out to confirm that the device will be able to reliably detect the heart’s rhythm from the subcutaneous position. A small number of patients do not pass this screening and require a transvenous device instead. Your electrophysiologist will assess which type of device is most appropriate for your individual situation.

Category: Children

A standard ICD uses leads that travel through a vein into the heart chambers, where they sense the heart’s rhythm and deliver shocks if needed. A subcutaneous ICD (S-ICD) does not enter the blood vessels or the heart at all. Instead, the lead is tunnelled just under the skin, running alongside the breastbone, and the device generator is implanted under the skin on the left side of the chest, below the armpit.

Because there are no leads inside the heart or blood vessels, an S-ICD avoids several risks associated with transvenous leads: lead fracture within the bloodstream, damage to heart valves, and bloodstream infections (endocarditis). It is also generally easier to remove if the device ever needs replacing or explanting.

The most important limitation of an S-ICD is that it cannot deliver ongoing pacing therapy or anti-tachycardia pacing (ATP). It can only detect a dangerous rhythm and deliver a shock. If you need continuous pacing — because your heart rate is too slow, or because ATP is part of your arrhythmia management — an S-ICD would not be appropriate on its own. This distinction is assessed before a device is chosen.

Category: Implantable Devices