Implantable Cardioverter Defibrillators (ICDs)
An “implantable defibrillator” is more correctly called an “implantable cardioverter defibrillator” or ICD for short. ICDs are intended for patients who have had or are at high risk for developing life-threatening rapid heart racing attacks called ventricular tachycardia (VT) or ventricular fibrillation (VF) that can lead to death. An ICD is larger in size than a regular pacemaker and many ICD models include all the features of a regular pacemaker. What makes an ICD different from a pacemaker is that, if and when a bout of VT or VF occurs in a patient, the ICD will either rapidly pace the heart to “overdrive” it, or deliver a shock to restore a normal rhythm. It is important to remember that an ICD does not prevent VT or VF attacks; they only stop them once they have occurred. ICDs have been shown in many large studies to significantly reduce the risk of death in certain groups of patients.
What are the parts of an ICD?
When a person receives an ICD, two basic parts are inserted: the ICD generator and one or more ICD leads (often called wires). The generator is often called the “battery”. In reality, a generator contains not only the battery but all the important wiring and circuitry that make the ICD work properly. In fact, generators are like miniature computers. ICD generators send out pacing pulses or shocks that are delivered to the heart by the ICD leads. ICD leads are inserted through the veins and the tips of the leads are attached to the heart. The other end is then hooked into the generator so that the electrical sparks can be sent down the lead to either pace or shock the heart when needed.
What is done in preparation for ICD implantation?
The first step in implanting an ICD is for doctors to establish that an ICD is needed. Once this decision is made and the operation date booked, you will be notified of the date and time. The ICD implantation operation is performed in a procedure room or operating room. Your physician may elect to discharge you the same day after the implant, or admit you for one or more days, depending on your specific needs.
In preparation for the operation, you will be given basic instructions by hospital staff. Usually, you will be asked not to eat or drink anything the morning of the operation. Someone else should drive you to the hospital and take you home afterwards. If you are taking medications, please ask the hospital staff contacting you if it is alright to take your pills the morning of the operation. Oral anticoagulants (also called blood thinner pills) often must be stopped several days before the operation. If you are taking them, please speak to a nurse at the hospital regarding your situation to obtain further instructions.
When you arrive for your procedure, staff will put an intravenous needle into a hand vein. Your doctor and other members of the team will then answer any of your questions before they transfer you into the operating room.
What are the risks associated with ICD implantation?
As with every operation, there are risks associated with ICD implantation.
During the procedure, there is a small chance that you could have an allergic or other adverse reaction to the medications that are given. Your doctor and nurses will be watching carefully for this and are prepared to deal with this if it happens. The implant procedure itself may be complicated by bleeding, infection, leakage of air from the lung into the chest cavity, dislodgment of the lead(s) or the creation of a hole in the heart. Generally, the risks are low and ICD implantation is considered to be a minor procedure.
After implant, there is a chance that the ICD components may perform less well than expected. This could lead to a recommendation to replace the ICD, lead(s) or both. Some companies also issue advisories about certain devices after implant. If this happens, your doctor will discuss the specific implications for you.
ICDs are designed to treat dangerous heart rhythms with either rapid “overdrive” pacing or a shock. However, sometimes the devices can be fooled, and they mistake a non-dangerous fast heart rhythm, or even electrical “noise”, for a dangerous heart rhythm. When this happens, the device may deliver what we call an “inappropriate shock”. Like all shocks, inappropriate shocks are painful, and therefore they are to be avoided. If you have an inappropriate shock, your doctor will work with you and your device to minimize the chance that it would happen again.
What can I do now that I have an ICD?
How long does an ICD last before it needs to be replaced?
An ICD generator lasts, on average, 4-7 years but it all depends on how much your body needs to use the device. It also depends upon how much electricity is needed to make the heart beat each time The more you use it and the more electricity required for each spark, the shorter time the device will last.
Why do I need to be seen in the Arrhythmia Device Clinic?
Every person who receives an ICD should have a regular checkup at least twice a year in Device Clinic. In the Clinic, the amount of battery power remaining is measured and the functioning of the ICD is assessed to make sure that the settings are correct, have not inadvertently been changed and that there are no signs of trouble with the generator or leads. It also allows the staff to ask how you are feeling in order to determine whether the ICD settings need to be changed to better meet your needs.
How often should I be checked in the Device Clinic?
Your physician will determine how often you need to be seen in the Device Clinic. If there are any concerns, you may be asked to return to the Clinic sooner or more frequently. If you received a research ICD, you may be asked to return more frequently for follow-up checks. Finally, as the battery power starts to get low and time to replacing the generator draws closer, more frequent checks may be needed.
Must my ICD follow-up checks all be done at the centre where I was implanted?
It is often possible for ICD checks to be done at the Device Clinic closest or most convenient to where you live. You should discuss follow-up with your physician before you go home.
More About ICDs
You have been referred to a specialist to discuss the risk of life threatening heart rhythm disturbances and whether an implantable cardioverter defibrillator (ICD) would be useful for you. This section is intended to provide information to you and your family/friends about what an ICD is, why it may be helpful to you, and the advantages and disadvantages of having an ICD.
What is an ICD?
An ICD is a medical device that is implanted under the skin much like a pacemaker but an ICD generator (or commonly called a “battery”) is larger. The ICD system consists of the generator (about half the size of a pack of playing cards) AND one or more wires (also called “leads”).
Two examples of ICD generators are shown with a two-dollar coin for size comparison.
The ICD leads connect the ICD generator to the heart so that it can monitor your heart beat, recognize when the heart develops a dangerously rapid racing and then automatically treat it with electric shocks. These shocks can reliably correct (“stop”) the abnormal heart rhythm that could otherwise be fatal.
The ICD also contains many features of a pacemaker, which treats any heart slowing that may occur. Some ICDs have a third wire that goes into the left side of the heart and is intended to improve the heart’s pumping function. Remember to discuss this with your doctor, since the decision regarding the number of wires is based on a number of factors specific to each patient’s case.
How is the ICD implanted or “inserted”?
The ICD generator is placed under the skin in the chest beneath your right or left collarbone. The ICD leads are inserted into a large vein that runs under your collarbone and are guided under X-ray to the heart. Implantation of an ICD is a small operation that will be performed in either a device implant room or an operating room. The procedure does not require major surgery such as opening the chest so a general anesthetic is not usually required. Patients are usually given mild sedation through the intravenous line to reduce anxiety. The doctor will inject local anesthetic (“freezing medication” or “dental freezing”) to numb the area. While the local anesthetic may sting as it is injected, once it takes effect, you should feel very little pain during the implant procedure.
During the implantation procedure, the doctor may wish to test the ICD to ensure that it works appropriately. If so, you will be put into a deeper sleep with more sedative medication through the intravenous line. The staff will then trigger your heart to race rapidly and instruct the ICD to give your heart a shock and take measurements to ensure that the ICD is working satisfactorily. Once that is completed, the incision is closed using sutures that dissolve on their own and do not need to be removed. A clear dressing that feels like plastic film wrap is placed over the wound to keep it clean. You are then taken from the procedure room to a recovery room to rest. A chest X-ray and electrocardiogram are performed and nurses will provide you with instructions about care of your wound and a follow-up appointment in the ICD Clinic. When you are sufficiently recovered, you will be discharged home.
How does the ICD work?
The ICD wires connected to the heart pick up the electrical signal coming from your heart as it beats and feeds that signal into the ICD generator. The ICD generator contains a battery and computer circuits that help it recognize when the heart is beating slowly or rapidly and dangerously. If and when the heart suddenly starts racing dangerously, the ICD detects this and the computers inside will tell the ICD to automatically give a shock to correct the heart rhythm or alternatively, deliver smaller electrical impulses to pace your heart gently out of the dangerous racing and back to normal. The ICD successfully corrects the heart rhythm in virtually all circumstances, but it does not affect why the event happened nor will it prevent it from happening again. Recurrences can only be prevented by heart medications or other procedures. Approximately one third of patients with an ICD take a medication to try to prevent the heart from racing.
What the ICD does when a dangerous heart-racing episode occurs depends upon how the ICD is programmed by the doctor and ICD Clinic nurse.
How is the ICD programmed?
The doctor or nurse can communicate and program the settings of an ICD specific to your needs and your type of medical problem. To do this, we use an ICD programmer, which is a laptop computer that sends radio waves to talk to the ICD inside your body. The ICD also stores information about what is happening to the device and can send that information back to the programmer by radio waves so the doctor or nurse can check the ICD regularly. To communicate with the ICD, the nurse will place a plastic disk that is connected to the programmer over the skin area where your ICD is implanted. These radio waves will not harm you.
What types of persons are considered for an ICD?
Two types of people are usually offered an ICD. The first type of person is someone who has already experienced one or more episodes of dangerous heart racing leading to blackouts or even cardiac arrest (commonly referred to as “heart stoppage”). Based on the circumstances and heart function, the doctor often recommends an ICD to protect patients in the event that the heart-racing episode returns. The second type of candidate for an ICD is a person who has had severe damage to their heart caused by such things as a previous heart attack or weakened heart muscle from leaky valves or previous viral infections. These people are at increased risk of having a fatal heart racing attack, even though it has not actually happened yet. Most patients who experience a cardiac arrest do not survive to receive an ICD. As a result, patients at risk for cardiac arrest may undergo ICD implant as a form of sudden death prevention.
What are the benefits of an ICD or why should I have one?
Your doctor has determined that you are at risk for having a dangerous and potentially lethal attack of heart-racing. These attacks can occur without advance warning at any time. The major benefit of an ICD is that it can prevent a patient from dying suddenly if an attack should occur and provides reassurance and peace of mind to the patient and family that he/she is protected from the tragedy of an unexpected sudden death. A useful analogy is to think of an ICD like one thinks of a fire extinguisher in the home. If you have one in the house, it can be used to put out a potentially dangerous fire should one occur BUT a fire extinguisher does not prevent a fire from breaking out in the house at any time. The same applies to an ICD. It cannot prevent a dangerous heart-racing bout from occurring but it can stop it if it happens. Major studies have established that the ICD reduces the risk of death in appropriately selected patients.
What are the disadvantages or risks of an ICD or why might I not want one?
The first concern is the risk of the implant procedure. There is no medical procedure that is without some risk. These risks will be explained to you before getting your consent to go ahead with the surgery. Minor complications such as minor bleeding or bruising, or pain at the surgery site occur about 2-5% of the time. Major complications from surgery, including collapsed lung, ICD lead falling out of the normal position or going through the heart wall occur about 1% of the time.
The second disadvantage is that the device may deliver shocks when the heart develops another kind of heart racing that is NOT dangerous. This happens in up to 25% of patients. Shocks can be painful and unsettling but can often be reduced or avoided after careful ICD re-programming or medications.
The third issue is that the ICD is a machine that is subject to normal “wear and tear” and needs to be checked regularly (approximately every 6 months) at the out-patient ICD Follow-up Clinic. During those visits, the battery strength is checked. A new battery usually lasts between 4-7 years. The ICD is also checked for any signs of malfunction. Rarely, ICD models can be made with serious defects that can cause the ICD to fail. Fortunately, this is very rare but is a limitation of all implanted devices.
Most patients feel better knowing that they have a device inside them that protects them but, in general, an ICD will NOT improve how much physical activity you can do. The only exception is a special three-wired ICD that is offered to certain patients meeting certain criteria. You are certainly welcome to ask the doctor during your visit whether you may be a candidate for such a special ICD.
Finally, the ICD does not prevent all sudden deaths nor will it affect death from poor heart function (heart failure) or other diseases such as kidney or lung disease, stroke or cancer. It can only prevent some deaths from dangerous rapid heart racing.
What things can I not do with an ICD?
We encourage patients receiving an ICD to resume as normal a lifestyle and physical activity as they were enjoying before the ICD. You can continue to operate household appliances including a microwave and radios. Please avoid putting magnets (even fridge magnets) on the skin over the ICD. Avoid being in areas where there are strong magnets and, for the time being, avoid MRI scans. When walking through security scanners or anti-theft scanners in airports or stores, walk straight through the detector gate as instructed without pausing. In general, having an ICD does not prevent you from driving a car. Driving licenses are usually suspended when you have had episodes of dangerous heart racing that required the ICD to treat and not because of the ICD itself.
Finally, things to think about…
Considering an ICD means thinking about end of life issues, which can be difficult for some people and their families. The ICD may affect how long you live, but for the most part does not affect how well you feel. Try to think about what you expect out of life, how enjoyable life is and how worried you are about the issue of sudden death. You should discuss this with your doctor, since an ICD is not for everyone.
Shocks are experienced by 10-30% of ICD patients each year. Most patients are aware of the shock, and describe it as painful. Although having an ICD often leads to peace of mind from the protection it provides, shocks can be stressful and can contribute to anxiety and depression in ICD patients. On the whole, most patients report that the device does not bother their everyday life, but receiving an ICD does involve recovery from the surgery and a minority of patients has ongoing discomfort from the implant.
** Source: Canadian Heart Rhythm Society