Implantable Cardiac Defibrillators (ICDs)
Arrhythmias that come from the bottom chambers of the heart pose a real risk for some patients with heart disease. When these arrhythmias occur, blood pressure drops quickly, and there is no chance for patients to call for help. Without immediate attention from providers trained in CPR or the use of an automated external defibrillator(AED), these arrhythmias are life threatening, and in the US, as many as 400,000 patients die per year from these types of arrhythmias. Conditions such as weakened heart muscle(CHF), or myocardial infarction are the most common causes of these arrhythmias, although some families may carry genetic traits which increase the risk of these arrhythmias, despite an otherwise normal heart.
For those at risk of sudden death syndrome due to severe arrhythmia, especially ventricular fibrillation, an implantable cardiac defibrillator or ICD is employed to provide protection. This device constantly is on the lookout for dangerous arrhythmias and if seen, it will charge up its battery to deliver a life saving shock. The standard ICD has been in use since the late 1980s and is implanted in a fashion similar to a pacemaker, whereby a wire is passed through the veins and into the heart, which is attached to a somewhat larger device which is placed beneath the skin. An ICD is indicated if patients have already had one documented life threatening arrhythmia, or if conditions exist which increase the risk of arrhythmias, such as weakened heart muscle, pumping power <35%, which doesn’t improve after stenting, bypass or optimal medical management.
More recently a new kind of defibrillator has been developed called the Subcutaneous ICD (S-ICD). The S-ICD is placed beneath the skin against the chest wall, but unlike the standard defibrillator, no wires go any deeper than just beneath the skin. In avoiding the need to pass wires into the circulation, and on into the heart, it is expected that this new device will carry fewer risks associated with both short and long term complications. Currently, the main difference between the standard ICD and S-ICD, is that the standard ICD also has the ability to act as a pacemaker, keeping the heart from going to slow. Absent the need for treatment for slow heart beats, the S-ICD is an equally effective tool to treat life threatening arrhythmias.