What is ICD implantation?
During an ICD implantation, an implantable cardioverter defibrillator (ICD) is inserted into the body. This is a device that detects life-threatening cardiac arrhythmias and terminates them with the help of a strong electric shock – which is why it is also called a “shock generator”. Its function is similar to that of a portable defibrillator, which emergency responders use during resuscitation efforts.
The ICD looks like a small box about the size of a matchbox. During ICD implantation, a doctor implants this box into the body, from where it then works permanently. The battery-powered ICD is usually implanted in the shoulder area just under the skin (subcutaneously). Electrode leads go from the device through large veins to the heart’s inner chambers (atria and ventricles). Depending on the number of probes, the following systems are distinguished for ICD implantation:
- Single-chamber systems: one probe in the right atrium or in the right ventricle
- Dual-chamber systems: two probes, one in the right atrium and one in the right ventricle
ICD devices are programmed individually and can thus be adapted to the needs of the respective patient.
How does a defibrillator work?
A normal defibrillator can effectively terminate so-called tachycardic arrhythmias (when the heart beats permanently too fast) in an emergency by delivering a high current pulse (shock). These cardiac arrhythmias include ventricular tachycardia, which can develop into ventricular fibrillation in an emergency. This is because the blood is no longer pumped properly through the body as a result of the heart beating too fast. Therefore, in case of ventricular fibrillation, immediate action must be taken, i.e. resuscitation measures by means of cardiac massage and defibrillation are necessary.
During defibrillation, the asynchronously beating, “fibrillating” heart is brought to a complete standstill for a few seconds by the high current pulse. After that, the heart starts beating again on its own and ideally in the right rhythm. This works similarly after an ICD implantation. The ICD can detect tachycardia through the electrode cable located in the heart and at the same time terminate it by delivering an immediate shock.
Differences to the pacemaker
Unlike the pacemaker, two probes are surrounded by metal coils to deliver a proper shock. An ICD can defibrillate in ventricular fibrillation, which a pacemaker cannot. However, an ICD can be combined with a pacemaker.
When is ICD implantation performed?
There are three main reasons why an ICD is implanted:
ICD implantation for primary prevention If an ICD is implanted to prevent the occurrence of a disease, it is referred to as “primary prevention.” Possible target groups here are patients who …
- … have an acquired heart condition (suffered a heart attack, coronary heart disease, cardiac insufficiency).
- … have a significantly reduced cardiac output (cardiac insufficiency) and thus a high risk of life-threatening cardiac arrhythmias (e.g. dilated cardiomyopathy).
The implantation of the defibrillator significantly reduces the probability of dying from so-called sudden cardiac death.
ICD implantation for congenital heart diseases If a person suffers from a genetic heart disease that is associated with an increased risk of cardiac arrhythmias, ICD implantation is also usually performed. These rare diseases include long and short QT syndrome, Brugada syndrome, and various heart muscle diseases (cardiomyopathy).
ICD implantation for resynchronization therapy
A defibrillator is also often implanted for cardiac resynchronization therapy (ICD-CRT or ICD-C). This therapy is mainly used in cases of severe cardiac insufficiency with significantly reduced ejection force of the heart (ejection fraction). In this case, there is often a disordered or asynchronous heartbeat: the right ventricle beats first and the left ventricle a few milliseconds later. By stimulating both chambers simultaneously using two chamber probes, the heartbeat can be synchronized again. As a result, ICD-CRT improves the heart’s pumping function and reduces the risk of dying from heart failure.
How is ICD implantation performed?
As a rule, the physician locally anesthetizes a spot below the collarbone and makes a small skin incision (a few centimeters long). There he looks for a vein (usually the subclavian vein) and inserts the probe(s) into the heart through it. The whole procedure is done under X-ray monitoring. After the defibrillator is inserted, the probes are then fixed to the chest muscle and then connected to the ICD device. The cardioverter itself is implanted in a small “tissue pocket” under the skin or pectoral muscle below the collarbone. Finally, the interface is sutured with a few stitches.
To test whether the ICD implantation was successful, the patient is put under brief anesthesia and ventricular fibrillation is induced. The defibrillator must detect this and deliver an electric shock. If everything works properly, the anesthesia is ended and the ICD is ready for use.
What are the risks of ICD implantation?
The most common complications include bleeding, infection, perforation of the heart walls or cable dislocation. To reduce the risk of complications, patients are given a single course of antibiotics (perioperative antibiotic administration) immediately before cardiovascular surgery. After defibrillator implantation, the patient receives anticoagulant medication to prevent blood clots.
Even after the defibrillator is implanted, complications cannot be ruled out. A frequent problem (up to 40 percent of cases) after ICD implantation is irregular shock delivery: if, for example, the ICD erroneously diagnoses a comparatively harmless atrial fibrillation as life-threatening ventricular tachycardia, it tries to terminate it by delivering multiple shocks, which is extremely painful and traumatizing for the patient. In case of doubt, the correct programming of the ICD must then be checked and possibly changed.
What do I need to keep in mind after ICD implantation?
Before discharge from the clinic (after about one week), the device system is checked again and programmed according to your needs. A second check-up is performed four to six weeks after ICD implantation.
Follow-up examinations after ICD implantation are very important. During this check-up, the physician checks that the ICD is functioning properly and, for example, checks the battery charge level.
See your cardiologist or a center with 24-hour emergency preparedness immediately if you suspect problems with the defibrillator, such as:
- Frequent irregular shock delivery.
- Suspected infection of the ICD system
- Worsening of heart failure
- Irregular heartbeat, etc.
Also, after ICD implantation, carry an appropriate identification card documenting the type of system implanted. And: certain medical procedures (MRI examination or various treatments with electric current) may no longer be allowed to be used on you, as they may affect the correct functioning of the ICD.