The implantable cardioverter defibrillator, also known as an ICD, was developed in 1980 and approved by the Food & Drug Administration (FDA) in 1985 – and its sole purpose is to prevent sudden cardiac death, also known as sudden cardiac arrest. This occurs when the heart stops beating suddenly due to a problem with the heart’s electrical system (arrhythmia), which stops blood flow to the body.
How ICD Works
The ICD is used to detect and stop these abnormal heartbeats – and it instantly tries to correct them by first trying to pace the heart out of the rhythm, which patients cannot feel. If pacing fails, the device then delivers one or more shocks to end the life-threatening rhythm.
Who Qualifies for an ICD
Patients who are at risk for sudden cardiac arrest, such as those who suffer from ventricular arrhythmias, or those who are at risk for them (such as individuals with a weak or enlarged heart muscle, or certain rare, genetic conditions) may be considered for an ICD.
Dr. Ashish Patel says that most patients with an ICD are those who suffer from congestive heart failure (CHF), although they’re also used for patients with rare structural conditions such as hypertrophic cardiomyopathy, too.
“Patients with CHF have a high incidence of sudden cardiac arrest due to ventricular arrhythmias. That’s why patients with an ejection fraction (a measure of how efficiently the heart is beating) of less than 35% are eligible for an ICD.”
He explains that the decision to move forward with an ICD is typically based on a combination of factors, including each patient’s risk factors and medical history, among others.
“It’s an important decision that most patients will make in partnership with their cardiologist,” Dr. Patel concludes.
Types of ICDs
Like most devices, ICDs continue to evolve and they’ve gotten smaller and more sophisticated. While early ICD devices were implanted in the abdomen, today there are three main types, including:
- A traditional ICD is implanted in the chest with wires (leads) that attach directly to the heart during an invasive procedure. Also known as a transvenous ICD, this device is implanted in the shoulder area. All transvenous ICDs also have built-in pacemakers (ideal for patients who also have bradycardia).
- The subcutaneous ICD (S-ICD) is a newer option that’s implanted using minimally-invasive techniques on the left side of the chest next to the rib cage with the lead placed under the skin (subcutaneously) above the breastbone. While it’s larger than a traditional ICD, this device leaves the heart and blood vessels completely untouched – meaning there are no leads or wires entering the heart.
- A biventricular ICD is a traditional ICD with a built-in biventricular pacemaker, so it’s ideal for patients with congestive heart failure who have electrical abnormalities like a left bundle branch block that lead to an abnormal contraction of the left ventricle. They’re implanted beneath the skin in the chest, just below the collarbone, and feature three leads placed in the heart.
Living with an ICD
ICD placement is typically an outpatient procedure, and most patients go home the same day. While having an ICD placed is generally a simple procedure, getting adjusted to life with an ICD can be difficult for some – particularly those who have survived a recent sudden cardiac arrest. In most cases, patients are also placed on medication(s) that work with the ICD to help the heart pump regularly. The good news is that while the ICD doesn’t change your underlying condition, it drastically reduces the risk of sudden death.
“Sometimes, patients who have a pacemaker or ICD implanted can have a hard time adjusting – but in most cases it’s more emotional than physical,” explains electrophysiologist Marc Silver, MD, FACC, WakeMed Heart & Vascular.
“Patients may become hypervigilant and concerned about whether it’s working, what to expect, etc. We try to talk our patients through these issues, and I remind them that we as cardiologists are very focused on the function of the device, so they don’t need to worry about that. In addition, devices are incredibly sophisticated these days – they do self-checks regularly and we get alerts if there are any concerns about malfunction.”
A Shock Plan
Once the device is placed, the ICD continuously monitors and records data on the heart rate and when and if needed, it will automatically provide the necessary treatment to get the heart rate back on track right away. Once an ICD is placed, the cardiologist develops a “shock plan” and explains what to do if a shock is delivered. Under certain circumstances, there’s no need to seek medical care, and in other cases, immediate medical attention is required.
Regardless of whether the device is used or not, the cardiologist will conduct a thorough evaluation of the device and its recordings generally four times per year to determine whether any changes need to be made to the course of treatment.
“For most patients, an ICD is like a silent protector that goes virtually unnoticed,” explains Dr. Silver. “In some patients, the ICD will never deliver a shock, but will resolve problems by pacing to correct the abnormal rhythm. In others, a life-saving shock can end a deadly rhythm. They save thousands of lives each year, giving many of our patients peace of mind after an alarming diagnosis or cardiovascular event.”
In some cases, patients with an ICD may be placed on driving restrictions either after the ICD is initially placed, or after the ICD delivers a shock. Fortunately, these restrictions are generally temporary and patients can get back to their normal routine after a few weeks or months.
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