What Is a Pacemaker and How Does It Work? A Clear Guide for Patients
- Faraz Afzal
- 4 days ago
- 3 min read
What Is a Pacemaker?
A pacemaker is a small electronic device that is implanted under the skin, usually just below the collarbone. It helps the heart maintain a steady and sufficient heart rate in people whose heart beats too slowly or when electrical signals are not properly conducted from the upper chambers of the heart to the lower chambers.
Why Do Some People Need a Pacemaker?
The most common reason is age related changes in the heart’s electrical conduction system. Over time, this system may no longer generate or transmit electrical signals effectively.
However, pacemakers may also be needed in younger patients, for example due to:
Congenital conduction disorders
Side effects of certain medications
Heart diseases that affect the electrical system
After specific procedures or illnesses, such as a heart attack
Different Types of Pacemakers
Most pacemakers have two leads (electrodes):
One lead placed in the right atrium
One lead placed in the right ventricle
This is called a dual chamber pacemaker and is the most common type.
When Is One Lead Used?
If a patient has permanent atrial fibrillation, stimulating the atrium often provides no benefit. In these cases, a pacemaker with a single lead placed in the ventricle may be used.
When Are Three Leads Used?
In certain forms of heart failure, a third lead may be placed on the left side of the heart through a vein on the outside of the heart. This is called a CRT pacemaker. It is used in patients with a specific type of conduction disorder and reduced pumping function.
How Is a Pacemaker Built?
A pacemaker consists of:
A battery and control unit, usually measuring about 3 × 3 cm to 6 × 6 cm depending on the model
One to three leads that travel through a blood vessel into the heart
Typical lead lengths are about 50 cm to the atrium and 60 cm to the ventricle, though this varies by manufacturer and patient size.
How Does a Pacemaker Work?
A pacemaker continuously monitors the heart. It:
Detects the heart’s electrical activity through the leads
Delivers an electrical impulse when the heart does not beat as it should
Basic Function: The Internal Clock
A pacemaker is programmed with a minimum heart rate, often around 60 beats per minute. This corresponds to an interval of about 1000 milliseconds.
If the heart beats on its own within this interval, the pacemaker does nothing
If the heart does not beat, the pacemaker sends an impulse to trigger a heartbeat
What Happens in AV Block?
AV block means that electrical signals are not properly transmitted from the atrium to the ventricle.
In this situation, the pacemaker acts as an artificial conductor:
It detects a beat in the atrium
Starts a short time interval, typically 140 to 200 milliseconds
If the ventricle does not beat within this time, the pacemaker stimulates it
This allows the ventricle to follow the rhythm of the atrium, even during physical activity. However, the pacemaker has an upper limit for how fast it can follow these signals. This is known as the maximum tracking rate.
Rate Response: Sensor Controlled Heart Rate Increase
Some patients are unable to naturally increase their heart rate during physical activity. In these cases, the pacemaker can increase the heart rate automatically.
It uses sensors such as:
An accelerometer that detects body movement
A respiration sensor that detects changes in breathing rate
These sensors can be programmed and adjusted as needed.
What a Pacemaker Does Not Do
A pacemaker does not treat fast heart rhythms.It does not help with conditions such as atrial fibrillation with a high heart rate or other tachycardias. Its purpose is to protect against heart rates that are too slow or against failed electrical conduction.
Common Conditions That May Require a Pacemaker
Sick Sinus Syndrome
The heart’s natural pacemaker in the atrium does not function properly. Patients may alternate between slow heart rates and episodes of fast atrial fibrillation.
AV Block
A conduction disorder between the atrium and ventricle that can range from mild delay to complete blockage.
Typical Symptoms Before Pacemaker Implantation
Dizziness
Fainting or near fainting episodes
Increasing fatigue
Slow heart rate
Unexplained shortness of breath
Alternating episodes of fast and slow heart rhythms
An ECG is the most important test to establish the diagnosis.
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