Introduction

The medical term for an enlarged heart is cardiomegaly.¹ It is a condition of the heart muscle that can be inherited, or caused by infections or pregnancy. An enlarged heart is not a disease but rather an indicator of an underlying condition. The most common causes of an enlarged heart are high blood pressure and coronary artery disease. However, any condition that forces the heart to work harder than usual can lead to cardiomegaly. 

Pacemakers are electronic devices that deliver electrical impulses to the heart to regulate or restore a normal heartbeat.² They are considered helpful in treating an enlarged heart as they help the heart keep a steady rhythm.

This article will explain why pacemakers are considered for patients with heart enlargement and highlight the role of pacemakers in improving heart rhythm and preventing complications.

What is heart enlargement?

An enlarged heart means you have a condition that has caused your heart to increase in size. This can be either the whole of your heart or just certain parts of your heart. The result of an enlarged heart is that your heart may not be able to pump your blood efficiently around the body. Having an enlarged heart can be severe, depending on the underlying cause. If the heart can not pump blood effectively, it can lead to heart failure.

Heart enlargement occurs when the heart is forced to work harder than usual to circulate blood. Sometimes, the enlargement can be due to a congenital heart condition (a disease or physical abnormality of the heart present from birth). Other common causes include high blood pressure, valve disease, cardiomyopathy, coronary heart disease, and idiopathic dilated cardiomyopathy.

The heart can be considered a pumping mechanism that sends blood around the body. Each heartbeat is the heart pumping. Each heartbeat sends an electrical signal through the heart’s internal conduction system. The heart contains specialised cells and nodes called the sinoatrial node and the atrioventricular node. These nodes control your heartbeat by sending and receiving electronic signals.³ Almost all cases of heart enlargement result in irregularities in the heart's rhythm (arrhythmias), including bradycardia and heart block.  An enlarged heart can not beat as evenly or efficiently as a heart of average size.

What is a pacemaker, and how does it work?

A pacemaker is a small electrical device fitted by surgical placement in your chest. It is a small battery-operated device measuring 5 by 4 centimetres, smaller than a matchbox. It helps your heart keep a regular rhythm by sending electrical impulses to your heart. This is used to help control abnormal heartbeats. 

If you need a pacemaker fitted, a small electrical device will be surgically implanted in your chest. Pacemakers are connected to your heart with tiny wires that allow electrical signals to pass through to your heart. The cables have electrodes on the ends, which detect abnormal heartbeats and send electrical signals to your heart to induce a normal rhythm.

There are three types of pacemakers:

• Single-chamber: These pacemakers use one lead, usually placed in the right ventricle (the lower right chamber of your heart)
• Dual chamber: The dual chamber uses one lead in the right atrium (the upper right chamber of your heart) and one in the right ventricle (the lower right chamber of your heart)
• Biventricular: These pacemakers use three leads. These are placed in the right atrium (the upper right chamber of your heart), right ventricle and left ventricle (left and right lower chambers of your heart). They are often used in heart failure patients

Image: Heart structure

Reference:https://upload.wikimedia.org/wikipedia/commons/2/2b/Anatomy_Heart_Tiesworks.jpg

Indications for pacemaker in heart enlargement

Sinus node dysfunction (Sick sinus syndrome)

Sinus node dysfunction may also be called ‘sick sinus syndrome’ or sinus node disease.

Sinus node dysfunction is a disorder which affects the heart's rhythm. It involves the heart's sinus node, the heart's natural pacemaker, as the node consistently generates electrical impulses.⁴ 

Enlargement of the heart can make it difficult for the heart to create and deliver these electrical signals effectively. People with sinus node dysfunction often eventually need a pacemaker to help maintain a regular rhythm when symptoms like fatigue, dizziness or fainting occur. 

Atrioventricular (AV) block

Atrioventricular (AV) block is when the electrical signals from the upper and lower chambers of the heart are either entirely or partially blocked. An enlarged heart can cause this condition as it struggles to generate electrical signals adequately. Treatment typically involves the fitting of a pacemaker.

Symptomatic bradycardia

Bradycardia is when the heart beats at a slower rate than usual. This often causes symptoms such as fainting/falls, dizziness, confusion, palpitations, chest pain and breathing difficulties. When these symptoms are present with bradycardia, it is known as symptomatic bradycardia. Symptomatic bradycardia is commonly caused by either sinus node dysfunction or atrioventricular block and can be treated using a pacemaker. 

Heart failure with conduction abnormalities

An enlarged heart can lead to heart failure. Heart enlargement can lead to difficulty receiving and sending electrical signals, worsening heart failure. Biventricular pacemakers are used to improve pumping efficiency in patients with heart failure caused by an enlarged heart by controlling the heart rate and reducing demand on the heart. 

High-grade AV block

High-grade AV block, also called advanced heart block, is a type of third-degree heart block. This condition happens when the electrical signals from the heart’s natural pacemaker (the sinus node) do not fully communicate with the heart's lower chambers (the ventricles). In this case, some of the electrical signals may occasionally reach the ventricles but not in a regular way. This differs from a complete heart block, where no signals from the sinus node reach the ventricles. To treat high-grade AV block, doctors typically implant a permanent pacemaker.

Criteria for pacemaker installation

The most common reason for getting a pacemaker is that the heart beats too slowly, a condition known as bradycardia. This can lead to fainting spells or other symptoms. Sometimes, a pacemaker is also used to prevent or treat a fast  (tachycardia) or irregular heartbeat.

These issues may be caused by:

• Problems with the electrical signaling in the heart
• Beta-blockers (medications that lower blood pressure but can also slow the heartbeat too much). A pacemaker can help maintain an appropriate heart rate when you need to continue taking this medication
• Certain congenital heart defects
• Heart attacks
• Heart transplants

Pacemakers are also indicated to assist individuals with weak hearts by helping their heart chambers beat in sync, mainly if the heart is not pumping enough blood to the body. This can occur due to:

• Certain congenital heart defects
• An enlarged or thickened heart muscle makes it more challenging to pump blood out of the ventricles.
• Heart attacks
• Heart failure

Pacemakers should be considered if a patient experiences symptoms such as:

• Dizziness
• Fainting
• Extreme fatigue

Other indications of the need for a pacemaker are:

• Severe arrhythmias occur when arrhythmias are severe and significantly impair heart function.
• Heart failure: If heart enlargement causes both heart failure and conduction abnormalities

When evaluating your need for a pacemaker, your specialist physician will assess the risk of complications, the severity of symptoms, and the effects on the patient's quality of life. 

Risks and considerations for pacemaker installation

Potential complications of a pacemaker device or its surgery may include:

• Infection: The risk for developing infection near the site in the heart where the device is placed is 0.5%–1% in the first 6–12 months following cardiac pacemaker implantation⁵
• Swelling, bruising or bleeding following surgery, especially if you take blood thinners
• Blood clots: About 2% of people with a pacemaker develop a blood clot near where the device is placed, usually in the arm on the side where the pacemaker is fitted
• Damage to blood vessels or nerves
• A collapsed lung: Pacemaker wires are inserted into veins which lie very close to one of the lungs. There is a small risk that one of these wires can accidentally puncture the lung, causing air leaks. This is known as pneumothorax
• Moving or shifting the device or leads could cause a hole in the heart. This complication is rare⁶
• Over-pacing: This is when the pacemaker stimulates the heart unnecessarily

Long-term care of a pacemaker

Every 6-12 months, your pacemaker must be checked to assess the battery and check how the wires are working. Eventually, the battery may need to be replaced. Pacemaker batteries usually last 10 to 15 years. A short surgical procedure will be required to renew the pacemaker batteries.⁷ Long-term medications must also be taken after the pacemaker is fitted. Regular check-ups with a healthcare provider will ensure all medications work effectively.

Alternatives to pacemaker treatment

• ICD: An implantable cardioverter defibrillator (ICD) is a device placed under the skin, similar to a pacemaker. It contains a computer that monitors your heart rate and rhythm. The critical difference is that if your heart beats too fast or goes out of rhythm, the ICD delivers a shock to restore a normal rhythm
• Medications: Antiarrhythmic drugs and beta-blockers to manage arrhythmias
• Surgical options include valve repair or heart surgery for structural issues causing heart enlargement
• Heart transplant in severe cases of heart failure
• Lifestyle modifications: Managing high blood pressure, avoiding excessive alcohol, and promoting heart-healthy habits

Summary

• The medical term for an enlarged heart is cardiomegaly
• An enlarged heart means you have a condition that has caused your heart to increase in size
• A pacemaker is a small electrical device fitted by surgical placement in your chest. It helps your heart keep a regular rhythm by sending electrical impulses to your heart
• The most common reason for getting a pacemaker is that the heart beats too slowly
• Potential complications are associated with a pacemaker device or its surgery, but they are rare
• Every 6-12 months, your pacemaker will need checking to assess the battery and check how the wires are working
• Long-term medications are also usually required to be taken after pacemaker insertion