What is a defibrillator?
The defibrillator (ICD) is an electronic device that constantly monitors the heart rhythm. When it detects a rapid, abnormal heart rate, it offers energy to the muscle, making the heart to return to its normal rhythm.
Why is an ICD needed?
Your doctor may recommend a defibrillator implantation if you had at least one event of this type or if there is a high risk that this happens (as in certain heart conditions).
As stated above, the defibrillator works as a monitor for abnormal heart rhythm and it identifies appropriate treatment to restore the normal beats. A defibrillator can have multiple functions, which your doctor will program as needed:
- Anti-tachycardia pacing (ATP) – when the heart beats very fast, the device will release several small electrical impulses to stop the fast rhythm and restore the normal rhythm.
- Cardioversion – in case of abnormal rhythm, an electric shock with low energy is released (as a stream of low intensity) that will overlap the heartbeat, so as to obtain normal rhythm.
- Defibrillation – when the heart beats very fast it can cause fatal events, but the device administers a great stream of energy to restore normal beats.
- Stimulation in case of bradycardia – when the heartbeat is rare, it releases tiny electrical impulses to sustain a normal heart frequency.
What is a defibrillator made of?
The defibrillator consists of:
- Pulse generator – it contains the battery (in which energy is stored that will be released if needed) and a mini-computer that will detect the heart rate, based on the information received.
- One or more probes- they are set at the level of the heart chambers, and they transmit their information to the mini computer, and also send electrical pulses from the generator, in case of abnormal heart beat
Types of defibrillators:
- Unicameral – shows a single probe that is fixed in the right ventricle, where the electrical impulses will be released if needed.
- Bicameral – there are two probes fixed in the right heart (one in the atrium and one in the ventricle); the electric impulse will initially be released in the atrium, then into the ventricle, producing stimulation similar to what normally happens in the heart.
- Biventricular – requires two probes (in this case one of them splits in the two cavities of the right heart) or 3 probes to be fixed in the right atrium and the right ventricle or the left ventricle (at the level of both ventricles; this type of stimulation is called cardiac resynchronization therapy). It allows maintaining the heart rhythm in a manner similar to the physiological course. It is a device used only in certain patients with heart failure.
Normally, the right ventricle and left ventricle (the lower chambers of the heart) contract at the same time. In case of heart failure, anomalies occur that so that the contractions are not simultaneously anymore, which leads to impaired additional heart function. Normally, the heart works like a pump that makes the blood to reach the body in sufficient quantity for all the organs and tissues, but in case of heart failure, the amount of blood decreases, which leads to multiple issues in the body and symptoms such as chest pain, shortness of breath, edema, kidney problems, dizziness, malaise.
The advantages of using this type of device are linked to improving heart failure, increasing the quality of life and the survival, increasing exercise capacity and decreasing the need for hospitalization.
This combination (defibrillator – biventricular pacemaker) allows ensuring a normal heart rhythm (whether the frequency is decreased or increased), ensures synchronous ventricular contraction, a record of the pace and heart rate.
There are two categories of indications: primary (preventing unwanted events before the first episode) and secondary prophylaxis (prevention after first episode)
- Patients who have already had an episode of cardiac arrest
- patients who previously had tachycardia (at least one episode)
- patients with prior myocardial infarction and who have increased risk of cardiac arrest or sudden death
- hypertrophic cardiomyopathy or other conditions that may predispose to arrhythmias (e.g., long QT syndrome)
- structural heart disease
- syncope (loss of consciousness)
- non-hospitalized patients awaiting heart transplant
- Brugada syndrome
- cardiac sarcoidosis, giant cell myocarditis, Chagas disease
It takes place in electrophysiology lab.
Implanting the defibrillator is a minimally invasive technique that involves fixing probes in the heart tissue (in the atrium and / or ventricle / ventricles – depending on the type of device) and attaching them to the generator pulse, which will be fixed either under the skin (most common method) or under the chest muscle.
To prevent infection, you will receive intravenous antibiotic, the area where the incision will be made is disinfected and you will be constantly monitored. A small incision in the left chest will be made, below the collarbone. Subsequently, the catheter (a thin plastic tube) will be inserted in a vein, through which the probes will be inserted into the heart. Usually, positioning the probe is under electrocardiographic and fluoroscopic control (following the right position through images).
The generator will be placed in a pocket under the skin at the incision site. Subsequently, the proper functioning of the device will be checked through specific tests, during which you will be asleep. Once the proper functioning is confirmed, the probes are attached to the generator. At the end of the procedure, an external device is used for setting certain additional parameters, in order to ensure optimal treatment. The wound is disinfected once again and is closed with sutures.
This technique involves transvenous approach, endocardic (when the probes are fixed inside the heart).
In some cases, this approach is not possible and surgery with general anaesthesia is needed. In this case, the probes will be fixed on the surface of the heart and the generator will be placed in a “pocket” in the abdomen (a technique called “epicardial approach”).
Is it painful?
The patient will not feel anything due to the local anaesthesia, and after surgery due to pain relievers (the incision site can be felt at the incision site) .In addition, you will be lightly sedated during surgery in order for the muscles to relaxes.
How long does it take?
Complications are rare and the risk of complications is low thanks to proper training and constant surveillance of the patient.
- allergic reactions to substances administered
- reactions to anaesthetics
- small bleeds, hematoma in the wound, pain
- immunological reaction – rarely
- abnormal function due to possible complications during the procedure (pneumothorax – air into the chest, pericarditis – an accumulation of fluid between the foils covering the heart, infections, skin erosions, hematoma, venous thrombosis). Optimal treatment of the complications can ensure normal functioning of the device. Erosion of the generator in the skin is rare, but can lead to the replacement of the device and requires administration of antibiotics. A change of the original position of the probes usually occurs in the first 2-3 days and can be seen on chest radiography. In this situation, if the probe is in the ventricle, it can produce severe rhythm disorders (arrhythmias).
- inadequate management of impulses
- rupture or dislocation of the probes
- fibrosis of the heart tissue at the site of the attachment of the probes
- pacemaker syndrome – the situation gets worse after the implantation
- Twiddler syndrome – the patient “plays” with the generator implanted under the skin, which can lead to various complications of the device
- damage of the subclavian artery or the lymphatic vessels
- pneumothorax, hemothorax (blood accumulation in the chest), hemopneumotorax (both blood and accumulation of air in the chest)
- pulmonary embolism, arrhythmias, tricuspid valve damage, cardiac perforation
- depletion of the battery of the generator
- upper limb venous thrombosis
- infective endocarditis
Before the surgery
Preoperative consultation will determine the type of device necessary and the background pathology.
Before the surgery, the doctor should be advised of the history of allergies and if there is suspicion of pregnancy. Also, any drugs used must be mentioned (especially antiplatelet or anticoagulants) or other associated diseases (diabetes, kidney disease).
A blood test is required to test the coagulation time, hemoglobin levels, renal function and, depending on the pathology associated, additional tests may be needed.
Admission in the hospital is done the day before surgery and in the morning of the surgery, the patient must not eat or drink anything.
Normally, this intervention can be performed without interrupting anticoagulation therapy, noting that INR values should not exceed therapeutic range. In case of antiplatelet treatment, it should be paused.
The doctor must also be warned about other followed treatments and, if necessary, some of them will require discontinuation.
An important element is the preoperative echocardiography. In cases of heart failure, a special cardiac ultrasound follows certain parameters on which one can say whether resynchronization therapy is necessary.
After the surgery
Due to the non-invasive nature of the procedure, the recovery is usually rapid. Most patients can leave the hospital after 1 day (only in case of epicardial approach it can be extended to 3-5 days). You will be given guidance on recovery and treatment to follow.
During the hospitalization you will be constantly monitored to detect any changes in the rhythm or the heart rate.
You will be instructed how to take care of the wound and when to return for suture wires suppression. You will also be warned that there is a limitation in the movement of your arm. A little discomfort may be felt 2-3 days after the procedure, and analgesic drugs can be taken.
You will get a card which contains details about the implanted device, which you will need to have on you on your subsequent checks.
It is important to know that the life period of a device of this type is between 3 and 6 years old, so repeated checks at the doctor are necessary.
It is also necessary to avoid exposure to electromagnetic fields (e.g. performing magnetic resonance) but many of the defibrillators are not affected. The information is available on the card.
It must be said also that although ICDs are extremely useful in stopping life-threatening arrhythmias, some patients require additional medication to reduce the frequency of producing these arrhythmias, and rarely, if drugs are not effective, ablation techniques may be needed (minimally invasive techniques which use probes to send small currents to the heart so that it closes the abnormal electrical circuit responsible for the onset of arrhythmias). Also, the shocks may be released in certain adverse conditions (atrial fibrillation, sinus tachycardia, or other arrhythmias that originate in the atria.)