Implantable Cardioverter Defibrillators
Implantable cardioverter defibrillators or ICDs are potentially life-saving devices that shock the heart back into rhythm if a dangerous arrhythmia is detected or if the heart is weakened from congestive heart failure, multiple heart attacks, or other heart diseases. ICDs look very much like a pacemaker in that they have a battery (pulse generator) with leads that connect the electrical impulse to the heart. These leads are either threaded through a vein or in the case of an S-ICD, are placed under the skin and run to the heart. Some ICDs can also act as pacing devices. However, when necessary, ICDs deliver a high-energy shock to restart the heart, a feature that pacemakers do not have.
In fact, you could liken an ICD to an implanted version of an automated external defibrillator or AED – a device that has become ubiquitous in public places and depicted in movies as delivering a lifesaving shock to the hearts of patients in need.
The Types of ICD
ICDs come in four flavors.
Single chamber ICDs are connected to the right ventricle with a single wire. Dual chamber ICDs use multiple wires to attach to the right atrium and right ventricle. Biventricular ICDs attach to three of the four chambers of the heart – the right atrium, right ventricle, and left ventricle. These are typically used for patients with heart failure and can improve symptoms and those for whom medication has not been successful.
Lastly, subcutaneous ICDs or S-ICDs have leads that run under the skin above the heart rather than through the vein. These can reduce the risk of infection. However, their pacing ability is limited, so they can only deliver an electrical shock to the heart in case of a dangerous arrhythmia.
Implanting an ICD
ICDs are implantable devices, and the process is as simple and straightforward as a pacemaker. First, Dr. Moretta will cut a small flap into the chest muscle within which the pulse generator or battery is fitted. Leads are threaded to the heart either through a vein or under the skin. These wires are connected to the battery. At this point, the device is calibrated and begins its work detecting any potentially deadly arrhythmias.
How Long Does the ICD Last?
The ICD typically lasts about 10 years though this largely depends on how often the device is deployed as well as the general care of the ICD. As the device approaches its end of useful life, Dr. Moretta can switch out the pulse generator in a very simple follow-up operation.
Benefits & Risks of an ICD
The benefits of an ICD are very clear. Sudden cardiac death or SCD is a significant concern in some patients that are prone to dangerous arrhythmias or that have advanced heart failure. Rather than rely on a third party to deploy an automated external defibrillator (AED), the ICD works without any external intervention. This not only offers a patient peace of mind but eliminates the time necessary to prepare the AED if one is even available.
The risks of an ICD are primarily those inherent to an implanted device including infection, malfunction of the device, and surgical complications including pain and bleeding at the incision site. These complications are relatively rare and can be mitigated by employing an experienced electrophysiologist.
There is also the risk of a false positive that triggers an electrical shock to the heart. These can be very disturbing to patients who may believe their heart is failing. While these false positives are rare, they are possible. Patients should take comfort in knowing that the device is working properly and thus in case of a true emergency, they have a lifesaving backup plan ready to deploy when necessary.
For more information about ICDs or to learn about effective ways to treat dangerous arrhythmias or heart failure that has not been successfully treated with medication or other interventions, we encourage you to schedule a consultation with Dr. Moretta.