The Subcutaneous ICD – Advantages & Limitations

Cardiology is a field that has progressed at a rapid pace. Over the years, there have been several innovative techniques to detect abnormality in the functions of heart even before the symptoms occur. The treatment of the severe heart conditions have evolved to an extent that man-made medical devices assist the heart to function properly and increase a person’s life expectancy, which was previously unimaginable.

These medical devices include a cardiac pacemaker and Implantable Cardioverter Defibrillator (ICD). An ICD is basically a pager-sized device which is placed in the chest to minimize the risk of death in case of the dangerous rhythm of the lower chambers of heart (ventricles) and the stoppage of the beats (cardiac arrest). ICD is an ideal medical device if the patient suffers from the condition of dangerously fast heartbeats (ventricular tachycardia). A chaotic heartbeat restricting the heart to supply enough blood (ventricular fibrillation) may also benefit from an ICD.

What is described above is a traditional ICD. A newer type of ICD called Subcutaneous ICD (or S-ICD) is also available at advanced surgical centers. The purpose of S-ICD is to detect and stop arrhythmias (abnormal heartbeats) by continuous monitoring and delivering electric pulses whenever there is a need to restore a normal rhythm of the heart.

The Subcutaneous ICD is placed under the skin below the armpit at the side of the chest. An electrode, which runs along the breastbone, is attached to the device. The patients who have structural defects in their hearts are ideal candidates for this device, but there can be other reasons too for avoiding a traditional ICD. The procedure to implant a Subcutaneous ICD is not as invasive as in the case of a traditional ICD. However, the S-ICD device is larger than an ICD.


  • There are no leads within the heart and the central venous circulation is effectively preserved.
  • It’s a great alternative for people, especially children, with congenital heart diseases or no venous access where the transvenous ICD would be an unsuitable option.
  • There is absolutely no risk of pneumothorax or vascular injury.
  • The risks of systemic infections are very low.
  • Any pocket infection that may occur, can be resolved with an antibiotic.
  • The implant procedure is simplified and there is no need for fluoroscopy.
  • There are cosmetic advantages as well despite the larger size of the device, because of the anatomic location it is placed on.
  • The device is comfortable for the patients.
  • There is minimum risk of myocardial damage despite the greater shock intensity (80 J), as the energy is more evenly distributed.


  • A screening is mandatory before implantation.
  • The inappropriate shocks range from 4% to 25%.
  • There is a risk that the true arrhythmias with very low amplitude waves would not be sensed properly.
  • The therapy time is prolonged as compared with the transvenous ICD.
  • There is a very few data available regarding the long-term performance in a real world scenario.
  • There is no pacing capability except the post-shock pacing.
  • The anticipated battery life is shorter than traditional devices.
  • Costs are high.