Subcutaneous Implantable Defibrillator (S-ICD)

Manufacturer	Boston Scientific
Website	(www.s-icd.eu)

The S-ICD System is a Subcutaneous (under the skin) Implantable Cardioverter Defibrillator for people who are at risk of Sudden Cardiac Arrest. The US S-ICD Patient Information website (www.sicdsystem.com) and European S-ICD Patient Information website (www.s-icd.eu) provides more information, including pictures of patients having a Subcutaneous ICD fitted and videos of patients talking about their experience of living with a Subcutaneous ICD.

Unlike a transvenous ICD, in which leads are fed into the heart through a vein and attached to the heart wall, the electrodes of the S-ICD are placed just under the skin and not in the heart; leaving the heart and veins untouched and intact.

One of the reasons the S-ICD was developed was to reduce the risk of complications associated with transvenous leads. Potential complications, such as infections in the bloodstream and the need to remove or replace the leads in the heart, are minimised or entirely eliminated with the S-ICD System.

Transvenous ICD (leads in the heart)

Pros

This pulse generator is smaller than the S-ICD pulse generator which may result in a less visible implanted device. This could improve the time needed to get used to the implantable device, although this is subjective.

Cons

The lead goes into the vein and heart and will grow into the heart wall over time. This may increase the chance of complications if the lead system needs to be removed or replaced, as the procedure to extract a cardiac lead can be a challenge. Because the lead needs to go into the heart it needs to be relatively thin and flexible, since it has to pass through (and remain in) the heart valve(s) and needs to flex with every heartbeat. This makes the lead more vulnerable to lead fracture (and therefore complications). Due to the position of the pulse generator under the collarbone, it can be more visible with certain clothing.

The S-ICD or Subcutaneous ICD (no lead in the heart but under the skin)

Pros

The lead does not go into the heart which means it leaves the vein and heart completely intact. This reduces chance of complications (e.g. systemic infections). Because the lead does not go into the heart it can be thicker and more robust. This minimizes / reduces the chance of lead fracture. In the event the system needs to be explanted, the procedure is a relatively simple surgical procedure.

Cons

The pulse generator is larger than most transvenous ICD pulse generators. This could result in a longer time needed to get used to it, although this is subjective. Depending on the physique of a person, the S-ICD may be more visible with bare chest.

Implant procedure Transvenous ICD versus Subcutaneous ICD

Transvenous ICD implant procedure	Subcutaneous ICD implant procedure
A transvenous ICD is typically implanted in the left shoulder area, near the collarbone. Occasionally the right side is preferred for certain patients or other specific reasons.	In contrast to a transvenous ICD, the pulse generator is implanted on the left side of the chest next to the rib cage, just under the arm, and the lead is implanted just under the skin above the breastbone.
Using X-ray imaging (fluoroscopy), the leads are fed through a vein into the heart and through the heart valve(s) into the heart.	Guided by anatomical landmarks and/or an X-ray image, the Subcutaneous ICD electrode is tunneled under the skin. The Subcutaneous ICD delivers therapy without the need for wires implanted in the heart.
Depending on your heart condition, 1, 2 or 3 leads will be placed in the heart. Once the leads are put in place, they are attached to the heart wall for optimal connectivity.	The Subcutaneous ICD leaves the heart and blood vessels untouched and intact.

External links

• http://www.s-icd.eu
• http://www.bostonscientific.com/en-EU/products/defibrillators/s-icd-emblem.html
• http://www.sicdsystem.com/en-US/home.html