Know Everything About Cardiac Pacemakers
Your heart tissue is made up of three layers. The outer layer is called the pericardium. The middle layer is called the myocardium. And the inner layer is called the endocardium.
The middle layer of the heart is composed of muscle cells called cardiomyocytes. Some of these cardiomyocytes have evolved to function for electrical conductivity and rhythm-making within the heart. This is why you might have noticed that your heart beats faster when you are ready to exercise, but it still beats rhythmically. You may also have seen that all the heart contractions are well aligned, even when beating up to 150 beats per minute or at 70 pages per minute. This is made possible by the unique distribution of specialist conducting fibres within the heart muscle.
These fibres work together to form nodes and conduct pathways, ensuring that all parts of the heart work melodiously and synchronously. The system begins with a group of cells at the top of the head called the sinus node. Then, each signal spreads from the sinus node to the bottom, which is met by another node called the AV node, which then supplies fibres to the heart muscles of the ventricles - causing the heart to contract and pump blood. You may read more about the heart's electrical system in our article here.
When this conducting pathway is blocked due to ageing, a heart muscle problem, or injury or trauma resulting from conditions like myocardial infarction, your heart might need extra support to ensure it beats fast enough to fulfil the body's needs. This is when an artificial pacemaker is recommended. That is when a pacemaker comes into play.
What is a pacemaker?
A cardiac pacemaker is a tiny electrical device with an electrical system that tells the heart when it's time to contract—modern pacemakers way as little as 25 to 28 grams.
They come in two parts: the generator, which contains the battery, the tiny computer with the information to control the heartbeat, and the leads, which are wires that lead from the generator and convey its signals to the heart. A pacemaker is usually implanted under the skin, and the procedure is a short one taking less than an hour to complete.
What are the types of cardiac pacemakers?
Cardiac pacemakers come in different types. Some of these include:
- A leadless pacemaker is a small device roughly the size of a large pill inserted using a catheter-based process. This device is installed on the inner wall of your heart, so additional wires are not needed.
- A single-chamber pacemaker carries electrical impulses to the right ventricle of your heart.
- A dual chamber pacemaker carries these impulses to the right ventricle and the right Atrium of your heart.
- A bi-ventricular pacemaker is a device that is used for cardiac resynchronisation therapy. This is used for people who have heart failure and heartbeat problems. This pacemaker stimulates the lower chambers of the heart, called the ventricles, to make the heart beat better.
What is cardiac resynchronisation therapy?
This procedure is used to implement a bi-ventricular pacemaker in the heart. It helps the ventricles contract coordinated and improves the heart pumping efficiency. Sometimes the device is attached to an Implantable Cardioverter Defibrillator or ICD. This device can reset the heartbeat when the heart becomes irregular.
This procedure is usually used for the treatment of people with heart failure or a condition called a left bundle branch block. Patients with heart failure already have weakened hearts. However, a lack of coordination between the different ventricles can lead to an even lesser pumping efficiency of the heart and further complications of heart failure. In such patients, cardiac resynchronisation therapy can improve the chances of a longer and more fulfilling life.
What conditions are pacemakers used to treat?
- Dysfunction of the Sinus node
- Block in the atrioventricular node
- Damage from a heart attack
- Heart failure
- Long QT syndrome
- Congenital complete heart block
What are the complications of pacemakers and Cardiac resynchronisation therapy?
Some of the complications of cardiac pacemakers include:
- Pacemaker Syndrome is a condition that reflects the consequences of a lack of proper atrioventricular synchronisation, even after pacemaker implantation. This constitutes dizziness, palpitation, dyspnea, loss of balance, and the presence of Cannon-A waves.
- Dislodgement of the leads
- Blood clotting
- Mechanical complications due to leads
- Malfunctions due to electrical interference
Cardiac resynchronisation therapy has the risk of the pacemaker as well as the surgery such as:
- Failure of the pacemaker
- Cardiac tamponade
- Shifting of parts installed within the body
How is the pacemaker installed in the body?
The pacemaker you use determines the procedure you must undertake to install it. However, recent advances in technology and surgical processes have made this a more straightforward system.
Some of the new approaches include:
- Catheter-based approach: This is used with a leadless pacemaker. However, the limitation of leadless pacemakers is that they can only treat conditions involving a single chamber of the heart.
- Transvenous fore approaching through a vein: This method is preferentially used in adults. Using a technique called fluoroscopy, the doctor will pass the wires are the leads through the vein and attach them to the heart. The other end of the leaves will be attached to the pacemaker device, which is implanted in a small pocket under your skin.
- Epicardial - An epicardial or surgical approach is made using a small incision in the chest, which leads towards your heart. Catheter-based procedures take less than an hour. Both transvenous and surgical methods take between two to five hours. Depending on your condition and type of pacemaker, your surgeon will suggest the best process for you.
Do pacemakers of batteries? How long will they last?
The battery life depends on the specific model and makes of your pacemaker. However, modern pacemakers can last between 10 to 15 years. Your doctor will also ask you to schedule follow-up appointments to check your device's status and your battery's health. Replacing the battery on a pacemaker is more straightforward than installing it the first time because it only requires access to the generator.