What Is an Implantable Cardioverter-Defibrillator?
An implantable cardioverter-defibrillator (ICD) is a small device that doctors put into your chest to help regulate irregular heart rhythms, or arrhythmias.
Although it is smaller than a deck of cards, the ICD contains a battery and a small computer that monitors your heart rate. The computer is programmed to deliver small electrical shocks to your heart at certain moments. This helps control your heart rate.
ICDs are most often used in patients who have life-threatening arrhythmias and are at risk of sudden cardiac arrest, a condition where the heart stops beating. Arrhythmias can be congenital (something you were born with) or a symptom of heart disease.
ICDs are also known as cardiac implantable devices or defibrillators.
Who Needs an ICD?
Your heart has four chambers—two atria (upper chambers) and two ventricles (lower chambers). Your ventricles pump blood from your heart to the rest of your body. Heart rhythm problems in your ventricles are very dangerous because your heart can stop pumping, causing you to pass out and die if you do not receive treatment immediately.
You might benefit from an ICD if you have:
- a very fast and dangerous heart rhythm (ventricular tachycardia)
- erratic pumping, referred to as “quivering” (ventricular fibrillation)
- a heart weakened by a history of heart disease or a past heart attack
- enlarged or thickened heart muscle (dilated or hypertrophic cardiomyopathy)
- congenital heart defects, such as long QT syndrome, which causes heart “quivering”
- heart failure
How Does an ICD Work?
An ICD is a small device implanted in your chest. The main device, called a pulse generator, holds a battery and tiny computer that monitors your heart rhythms. If your heart beats too fast or irregularly, the computer delivers an electric pulse to correct the problem.
Wires, called leads, run from the pulse generator into specific areas of your heart. These leads deliver the electric impulses that are sent by the pulse generator.
Depending on your diagnosis, your doctor may recommend one of the following types of ICDs:
- single-chamber ICD: sends electrical signals to the right ventricle
- dual-chamber ICD: sends electrical signals to the right atrium and right ventricle
- biventricular device: sends electrical signals to the right atrium and both ventricles, and is used specifically in patients with heart failure
An ICD can also be programmed to deliver up to four different types of electrical signals to your heart.
Cardioversion gives a stronger electrical signal that can feel like a thump to your chest. It is used to reset heart rhythms to normal when a very fast heart rate is detected.
Defibrillation sends a very strong electrical signal that restarts your heart. The sensation is painful and can knock you off your feet, but lasts only a second.
Anti-tachycardia pacing provides a low-energy pulse meant to reset a rapid heartbeat. Typically, you will feel nothing when the pulse is given. However, you may sense a small flutter in your chest.
Bradycardia pacing restores a too-slow heartbeat to normal speed. In this situation, the ICD works like a pacemaker. People with ICDs usually have hearts that beat too fast. However, defibrillation can sometimes cause the heart to slow down to a dangerous level. Bradycardia pacing would then be used to return the rhythm to normal.
Preparing for an ICD Implant Procedure
Preparations for an ICD implant are generally simple. You should not eat or drink anything after midnight on the day before your procedure.
Your doctor may also ask you to stop taking certain medicines, such as aspirin or those that cause blood clotting beforehand. Be sure to tell your doctor about the medications, over-the-counter drugs, and supplements you take before the procedure. Never stop taking a medication without talking to your doctor first.
What Happens During an ICD Implant Procedure?
An ICD implant procedure is minimally invasive. The device is usually implanted in an electrophysiology laboratory by an electrophysiologist. In most cases, you will be awake during the procedure. However, you will receive a sedative to make you drowsy and a local anesthetic to numb your chest area.
After making small incisions, the doctor will guide the leads through a vein and attach them to the specific muscles of your heart. An X-ray monitoring tool called a fluoroscope may help guide your doctor to your heart.
He or she will then attach the other end of the leads to the pulse generator. A small incision will be made and the device will be placed in a pocket of skin on your chest, most often under your left shoulder.
The entire procedure typically takes between one and three hours. Afterwards, you will stay in the hospital for at least 24 hours for recovery and monitoring. You should feel fully recovered within four to six weeks.
An ICD may also be implanted surgically under general anesthesia. In this case, your hospital recovery time can last up to five days.
What Risks Are Involved?
As with any surgery, an ICD implant procedure may cause bleeding, pain, and infection at the incision site, or an allergic reaction to medications used during the procedure.
More serious problems specific to this procedure are rare. However, they can include:
- blood clots
- damage to your heart, valves, or arteries
- fluid buildup around the heart
- heart attack
- collapsed lung
It’s also possible that your device will occasionally shock your heart unnecessarily. Although these shocks are brief and not harmful, you will usually feel them. If there is a problem with ICD, it may need to be re-programmed by your electrophysiologist.
Recovering After the Procedure
Depending on your situation, recovery can take anywhere from a few days to a few weeks. You should avoid high-impact activities and heavy lifting for at least a month after your procedure.
The American Heart Association (AHA) discourages driving for at least six months after an ICD implant procedure. This gives you a chance to assess whether a shock to your heart will cause you to faint (AHA , 2002).
Living with an ICD
An ICD is a lifelong commitment.
After you recover, your doctor will meet with you to program your device. You should continue to meet with your doctor about every three to six months. You should be sure to take any prescribed medications and adopt the lifestyle and diet changes your doctor prescribed.
The batteries on the device last for five to seven years. You will need another procedure to replace the batteries. However, it is slightly less complicated than the first.
Certain objects can interfere with your device’s performance, so you will need to avoid them. These include:
- security systems
- certain medical equipment, like MRIs
- power generators
You may want to carry a card in your wallet or wear a medical ID bracelet that states what type of ICD you have. In addition, try to keep cell phones and other mobile devices at least six inches away from your ICD.
Tell your doctor if you are experiencing any problems with your device, and call your doctor immediately if your defibrillator delivers a shock to restart your heart.