Pacemaker: A Complete Guide for patients

What Is a Pacemaker?

A pacemaker is a small electronic medical device implanted under the skin, usually just below the collarbone. Its primary purpose is to help the heart maintain an adequate and regular heart rate when the heart’s own electrical system is too slow or unreliable.

Pacemakers are used in patients with bradycardia (slow heart rate) or impaired electrical conduction between the atria (upper chambers) and the ventricles (lower chambers). They are among the most commonly implanted cardiac devices worldwide.

Dual-chamber pacemaker

Why Do Some People Need a Pacemaker?

The most common reason for pacemaker implantation is age-related degeneration of the heart’s electrical conduction system. Over time, the system that generates and transmits electrical impulses may slow down or fail intermittently.

Other Reasons a Pacemaker May Be Needed

Pacemakers may also be required due to:

• Congenital conduction disorders

• Side effects of medications such as beta blockers or antiarrhythmic drugs

• Heart diseases affecting the electrical system

• Damage after a heart attack

• Certain cardiac procedures or inflammatory conditions

  
  

Different Types of Pacemakers

Pacemakers consist of a pulse generator and one or more leads (electrodes) that deliver electrical impulses to the heart.

Dual-Chamber Pacemaker (Most Common)

A dual-chamber pacemaker has:

• One lead in the right atrium

• One lead in the right ventricle

  
  

This allows coordinated activation of the atrium and ventricle and closely mimics the heart’s natural rhythm.

When Is a Single-Lead Pacemaker Used?

In patients with permanent atrial fibrillation, pacing the atrium provides no benefit. In these cases, a single-lead pacemaker placed in the right ventricle is usually sufficient.

When Is a Three-Lead (CRT) Pacemaker Used?

In selected patients with heart failure, reduced pumping function, and a specific electrical conduction disorder, a third lead may be placed on the left side of the heart. This treatment is called cardiac resynchronization therapy (CRT).

How Is a Pacemaker Built?

A pacemaker consists of:

• A battery and control unit (pulse generator), typically 3 × 3 cm to 6 × 6 cm in size

• One to three insulated leads that travel through blood vessels into the heart

Lead length usually ranges from approximately 50 cm to the atrium and 60 cm to the ventricle, depending on patient size and manufacturer.

How Does a Pacemaker Work?

A pacemaker continuously monitors the heart’s intrinsic electrical activity.

Core Functions

• Detects natural heartbeats

• Delivers a small electrical impulse when no heartbeat occurs within a programmed time interval

  
  

The Internal Clock (Base Rate)

Pacemakers are programmed with a minimum heart rate, commonly around 60 beats per minute (≈1000 ms interval).

• If a natural beat occurs, the pacemaker remains inactive

• If no beat is detected, the pacemaker stimulates the heart

  
  

What Happens in AV Block?

Atrioventricular (AV) block occurs when electrical signals from the atrium are delayed or fail to reach the ventricle.

Pacemaker Function in AV Block

• Detects atrial activity

• Starts a programmed delay (typically 140–200 ms)

• Stimulates the ventricle if no intrinsic beat occurs

This maintains atrioventricular synchrony, even during physical activity. The pacemaker also has a maximum tracking rate that limits how fast it can follow atrial signals.

Rate Response: Sensor-Controlled Heart Rate Increase

Some patients cannot naturally increase their heart rate during physical activity.

Pacemakers can compensate using:

• Accelerometers that detect movement

• Respiration sensors that respond to breathing changes

  
  

These features are programmable and individualized.

What a Pacemaker Does Not Do

A pacemaker does not treat fast heart rhythms. It does not prevent or terminate tachycardias such as atrial fibrillation with rapid ventricular response.

Its role is to prevent heart rates that are too slow or to compensate for failed electrical conduction.

Common Conditions That May Require a Pacemaker

Sick Sinus Syndrome

The heart’s natural pacemaker does not function properly, leading to slow heart rates, pauses, or alternating bradycardia and atrial fibrillation.

Atrioventricular (AV) Block

A conduction disorder ranging from mild delay to complete electrical block.

Typical Symptoms Before Pacemaker Implantation

• Dizziness

• Fainting or near-fainting episodes

• Increasing fatigue

• Persistently slow heart rate

• Unexplained shortness of breath

• Alternating fast and slow heart rhythms

  
  

An electrocardiogram (ECG) is the most important diagnostic test.

FAQ – Pacemaker

What is a pacemaker used for?

To maintain an adequate heart rate when the heart’s electrical system is too slow or unreliable.

Is a pacemaker the same as a defibrillator?

No. Pacemakers treat slow rhythms, while defibrillators treat dangerous fast rhythms.

Can a pacemaker adjust to physical activity?

Yes. Many pacemakers use sensors to increase heart rate during activity.

Does a pacemaker cure heart disease?

No. It treats electrical rhythm problems but does not cure underlying heart disease.