Overview of Automatic Internal Cardiac Defibrillator
An Implantable Cardioverter Defibrillator (ICD), also known as an automated internal cardiac defibrillator or “shock box,” is a modern piece of technology that helps in managing irregular heart rhythms, specifically those that start in the ventricles, or lower chambers of the heart. These kinds of irregular heart rhythms can include ventricular tachycardia, which is a fast heart rate that starts in the ventricles, and fibrillation, which is when the ventricles quiver instead of pumping properly. The ICD is considered a crucial tool in saving patients who are at a high risk of sudden cardiac death, helping patients survive a cardiac arrest and benefiting those with heart failure, especially when their heart’s pumping strength (or left ventricular ejection fraction) is severely reduced (below or equal to 35%). It’s also proven useful for patients with hypertrophic cardiomyopathy, a disease where the heart muscle becomes abnormally thick.
An ICD can be thought of as a pacemaker that not only can control the heart’s rhythm, but can also understand when your heart is beating too fast. The ICD can respond immediately to this issue by either using a function known as anti-tachycardia pacing (ATP), which outpaces the fast rhythm to normalize it, or by sending a shock therapy, depending on the type of rhythm detected and based on its pre-set programming. ICDs come in three types: single lead or single chamber, dual lead or dual-chamber, and a version combined with cardiac resynchronization therapy (CRT-D). The CRT-D model is essentially a bi-ventricular device with wires (leads) in not just one, but both the right atrium and ventricle and the coronary sinus, a collection of veins that join to form a large vessel that collects blood from the myocardium (heart muscle). Due to its closeness, the coronary sinus lead is often referred to as the left ventricle lead.
In 2012, a subcutaneous ICD (S-ICD) that uses leads placed under the skin instead of inside the heart was approved by the US Food and Drug Administration. More recently, wearable defibrillators have been introduced for short-term use. These are designed to provide temporary protection from abnormal heart rhythms.
Why do People Need Automatic Internal Cardiac Defibrillator
In simpler terms, we install a device (implantable cardioverter-defibrillator or ICD for short) in a patient’s heart under two circumstances. The first one is called “secondary”, meaning they have already had a significant heart-related event like a sudden stoppage of the heart due to dangerous heart rhythms (referred to as ventricular fibrillation or ventricular tachycardia). The second scenario is known as “primary”, where we install the device in patients who haven’t experienced these heart events but have a high risk of doing so. In both situations, the ICD device could save a life by automatically correcting the abnormal heart rhythm when detected.
Before deciding to install this device, doctors will meticulously check for reversible causes or conditions that could have caused the heart’s frightful behavior. We do this to ensure the person truly needs an ICD by following guidelines from well-respected heart health institutions like the Heart Rhythm Society and the American College of Cardiology.
More commonly, these devices are introduced as “primary prophylaxis” to patients who haven’t had sudden heart stoppage but are extremely likely to experience it. They are often recommended for patients if their heart isn’t pumping blood efficiently (what we call “LV dysfunction with an ejection fraction less than or equal to 35%”) and also have symptoms indicating the lower function of their heart (defined as “NYHA II/III symptoms”). The ICD is also recommended for those who have had a heart attack (or “myocardial infarction” in medical terms) in the past and are experiencing symptoms or for those who have temporary unconsciousness, causing an unknown origin (known as “syncope”). In these cases, activating the dangerous heart rhythm in a controlled environment (EPS study) can help guide the decision to implant an ICD or not. Ultimately, the ICD is also indicated in cases of dangerous but continuous heart rhythms in individuals with pre-existing heart disease.
When a Person Should Avoid Automatic Internal Cardiac Defibrillator
An Implantable Cardioverter Defibrillator (ICD), a device that can correct an abnormal heart rhythm, may not be suitable for everyone. If someone has conditions that can be fixed, such as a lack of blood flow to the heart (myocardial ischemia), a serious body-wide infection (sepsis), not enough oxygen in the body (hypoxia), an imbalance in the body’s minerals (electrolyte imbalance), or a recent electrical injury (electrocution), which lead to fast heartbeats that can cause sudden cardiac arrest (VT/VF), then using an ICD might not be the best option.
If a person has irregular heartbeats from the upper chambers of the heart (atrial arrhythmias) without any associated VT/VF, or if the fast heartbeats happens continuously (incessant VT/VF), it may also not be suitable to use an ICD.
Equipment used for Automatic Internal Cardiac Defibrillator
The ICD, or Implantable Cardioverter Defibrillator, is a device composed of three main parts:
1. The pulse generator: This is a small pod-like structure that holds sophisticated technology. It is responsible for keeping track of your heart’s rhythms, storing these tracings, and recognizing when your heart is acting unusually. If it determines that your heart needs help, it can deliver a pre-programmed treatment to help return your heart to its normal rhythm. This treatment could be Anti-Tachycardia Pacing (ATP) – a gentle rhythm to discourage rapid heartbeats – or it could administer a stronger defibrillation shock if needed. This generator is implanted under the skin, typically in the chest region. It also holds the battery and a device to support your heart’s function if required, though these have a limited charge and lifespan. This part of the ICD also features a code from the manufacturer that can be read on a specific type of X-ray known as a plain radiogram. The device’s magnet is placed over the pulse generator for things like inhibiting unwanted signals, checking device function, or adjusting treatment plans. What’s more, it has the ability to wirelessly communicate with compatible devices within a certain distance.
2. The leads: These are like the cables connecting the pulse generator to your heart. They are coated in a silicone material and contain electrodes that allow signals to pass between the pulse generator and your heart muscle. These leads rest inside your heart. One end is hooked to the ICD device, and the other end is secured within a chamber of the heart.
3. The shocking coil: Found within the ICD leads, this delivers the needed electrical charge for defibrilling or shocking the heart back into a normal rhythm when necessary. It can be located on an X-ray by looking for spiral shaped thicknesses towards the heart end of the lead and in the Superior Vena Cava region on the atrial lead.
Who is needed to perform Automatic Internal Cardiac Defibrillator?
The choice to get an ICD (implantable cardioverter defibrillator) is made by your main doctor. An ICD is a small device placed in your chest to help control irregular heartbeats. If your doctor thinks you might need one, they will typically refer you to two kinds of heart specialists. One is a cardiac electrophysiologist, a doctor who specializes in your heart’s electrical system and treats irregular heart rhythms. The other is a rhythm device specialist, who focuses on devices used to manage heartbeats. These experts will properly check you and plan the procedure if needed.
Preparing for Automatic Internal Cardiac Defibrillator
Before a medical procedure, patients often need to take several steps to prepare. This typically includes a full body wash to clean the skin and lower the risk of infection. This wash is typically done 24 hours before the procedure. Another important step is not eating or drinking anything (also known as being NPO) for at least 4 hours before the procedure.
Also, doctors need to check blood work, which includes the platelet count (the number of tiny blood cells that help your body form clots to stop bleeding) and the INR (a test that measures how quickly your blood clots). This helps make sure everything is in order before the procedure. For those with diabetes, another test called HbA1c is done. This test shows an average of how much sugar has been in your blood over the past 2-3 months. Keeping blood sugar levels controlled is very important to reduce the risk of infections.
In some cases, the doctors might tell the patient to temporarily stop taking certain medications that prevent clotting, referred to as anticoagulants (e.g., warfarin, NOACs, DTIs). This is done to ensure there are no potential bleeding problems during the procedure. As each person’s condition is different, the doctor will give specific instructions to prepare for the upcoming procedure.
How is Automatic Internal Cardiac Defibrillator performed
In this procedure, the patient is carefully prepared in a clean environment, similar to how a pacemaker surgery is done. The chest area is exposed and carefully cleaned. The procedure is typically performed while the patient is awake but relaxed, with local anesthesia used to numb the surgical area.
The device is placed under the skin, typically in the chest area. A small pocket is created to hold the device, and wires, or leads, are connected from the device to the heart. The leads are carefully threaded through a vein in the chest (the subclavian vein) and positioned so they can monitor or stimulate the heart. Some doctors may also check the lowest amount of energy needed to regulate your heartbeat, although there isn’t a universal agreement on this. Once this testing is complete, the small pocket for the device is closed up.
The entire procedure can take up to 90 minutes.
Although patients can usually go home on the same day, they often spend the night in the hospital. The next day, they are discharged home after the device is checked again and a simple chest X-ray is done to confirm that the leads are in the right place.
Possible Complications of Automatic Internal Cardiac Defibrillator
After a medical procedure, there might be early complications (short-term) or issues happening much later (long-term).
Short-term complications, which only affect about 2 to 3% of patients, happen right after the procedure. These could include:
1. Problems when gaining access to the treatment area, like bleeding, blood clotting in veins around the collarbone area or accidentally poking the lung tissue, which could result in a pneumothorax (collapsed lung) or a hemothorax (blood in the space between the chest wall and the lung).
2. Complications around the inserted device or implant, like pain, pocket hematoma (an abnormal collection of blood outside of a blood vessel), and uniquely, Twiddler syndrome. This last one involves the device getting twisted and misplaced, often due to pressure from a growing hematoma, causing the device to not work properly as lead and generator connections get affected.
3. Infections related to the device, which includes a particularly serious one called endocarditis (inflammation of the heart’s inner lining). This happens in about 1 to 2% of cases.
4. Severe complications, which are quite rare (less than 1%), such as pulseless electrical activity (a type of cardiac arrest where the heart rhythm looks almost normal, but the heart muscles don’t respond and don’t beat) or even death. These can occur during a defibrillation threshold test (DFT, a check to see if the defibrillator device is working properly).
Long-term complications, which happen to up to 4% of patients, can include:
1. Pain linked to the device,
2. Anxiety,
3. Fracture of the lead (the wire that connects the device to the heart),
4. The device giving shocks when it shouldn’t,
5. Phantom shock: the patient feels like they’ve been shocked by their device, but checks don’t show any such shock or event has happened,
6. The device poking through the skin,
7. Infections due to the device, especially if the device has been replaced or the battery pack (generator) has been changed,
8. Immunologic rejection, where the body’s defense system attacks the device like it’s a harmful invader. This is very rare.
What Else Should I Know About Automatic Internal Cardiac Defibrillator?
Implantable cardioverter defibrillators, or ICDs, are devices that have been used since the late 1980s and can greatly increase survival rates for individuals at high risk of cardiac arrest. They continually improved over the years in both efficiency and design and can lend a crucial hand to those who might not otherwise reach the hospital in time during a critical heart event.
Patients with heart diseases that cause structural changes, as well as heart diseases that weaken the heart muscle (cardiomyopathies), can benefit from this device. This includes both heart diseases caused by narrowed or blocked blood vessels (ischemic) and diseases not caused by blood vessel problems (non-ischemic). These benefits are even more pronounced when the ICD is used together with a therapy called resynchronization therapy. This combination can improve quality of life, improve survival rates, and even potentially help improve a measure of heart function known as the left ventricular ejection fraction (LVEF), which is the amount of blood the left ventricle of your heart pumps out with each contraction.
Moreover, these devices can provide constant protection to individuals awaiting a heart transplant. While they wait for a suitable donor, the ICDs or CRT-Ds (cardiac resynchronization therapy defibrillators) can help monitor their heart’s activities and ensure they get to live up to their transplant date.
