Introduction

The brain and heart are deeply interconnected, especially regarding stroke risk. Heart enlargement can significantly raise the likelihood of stroke by disturbing normal blood flow and triggering complications that impact both organs. Recognising this connection is essential for effectively managing and reducing stroke risk associated with heart conditions.

What is heart enlargement?

Heart enlargement, also known as cardiomegaly, is a condition where the size of the heart is more than 50% of the transverse diameter of the rib cage.¹ An increase in the area of the heart may affect the right and left or all ventricles of the heart’s upper chambers. The enlarged heart can develop in two ways: thickening (hypertrophy) of the heart wall and stretching (dilating) of the heart walls.

What is a stroke?

Stroke is a serious neurological condition in which the brain's blood supply is disrupted. This happens either due to a blockage in the blood vessels (ischemic stroke) or during sudden bleeding in the brain (known as a hemorrhagic stroke).²

Understanding the link between heart enlargement and stroke risk

The link between an enlarged heart and the possibility of having a stroke helps in early detection, which can significantly prevent serious health issues. As the heart dilates, it is unable to pump blood as necessary, thereby interrupting the normal pattern of blood flow and resulting in the formation of blood clots. These clots may reduce the blood flow to the brain, leading to a stroke.³ Therefore, a timely approach can reduce the risk of adverse outcomes and enhance the functioning of the heart and brain.

What causes heart enlargement 

Several factors are responsible for an enlarged heart, which include:⁴

• High blood pressure 
• Heart valve disease (e.g., aortic stenosis) 
• Coronary artery disease 
• Cardiomyopathy 
• Congenital heart defects 
• Impact of lifestyle factors (e.g., obesity, alcohol)

Mechanisms linking heart enlargement to stroke

Atrial fibrillation

When the heart size increases, particularly the top chambers of the heart (the atria), it can interfere with the heart’s electrical system to stop working properly. This leads to an irregular or rapid heartbeat, which is referred to as atrial fibrillation.

In atrial fibrillation, the heart doesn’t pump blood as it is supposed to, which can result in the formation of blood clots in the heart. If one of these clots travels to the brain, it can obstruct blood flow and cause an ischaemic stroke.³

Reduced heart function 

When the left atrium is enlarged beyond its normal size, it can weaken the heart’s ability to contract efficiently. This lowered ability to contract means that the blood does not flow through the chamber as strongly, which can result in stagnant blood. The reduced flow with slow or stagnant blood makes it more susceptible to clot formation (thrombosis) because blood cells are more easily aggregated within non-moving or slow-moving blood.⁵ If a blood clot is formed, it can potentially travel to the brain, which can cause a stroke.

Left ventricular hypertrophy and vascular stiffness 

Left ventricular hypertrophy (LVH) is a condition of the left bottom chamber of the heart, which is thickened due to high blood pressure or obesity. This gradual thickening is associated with stiffer blood vessels, especially inside the carotid arteries that supply blood to the brain. Stiffness of these arteries along with high blood pressure and irregular heartbeat (atrial fibrillation), which can occur with LVH, raises the likelihood of blood clot formation.⁶ These clots can significantly increase the risk of stroke.

Symptoms and diagnosis of heart enlargement

Symptoms of heart enlargement

While some people with an enlarged heart may not show any symptoms, others might experience:⁷

• Shortness of breath on activity or rest
• Oedema (also known as swelling) in the abdomen, hands and feet
• Feeling tired
• Lightheadedness
• Poor tolerance to exercise
• Pounding heartbeat

Diagnostic tools 

The doctor will perform a physical exam and discuss your concerns, followed by a range of tests to check the condition and function of the heart. Imaging techniques are most commonly used to assess the size and functioning of the heart and diagnose an enlarged heart. These imaging techniques and other diagnostic testing include:⁷

• A chest X-ray takes photos of the heart and the chest ¹
• A transthoracic echocardiogram uses sound waves to create images of the heart’s size and check the movement of the heart
• Magnetic resonance imaging (MRI) uses strong magnets and radio waves to provide images of the heart
• An electrocardiogram (ECG) measures the heart's electrical activity
• A stress test is performed to see the functioning of the heart when put under stress, i.e exercise
• Computerised tomography (CT) scans use chest X-rays that provide detailed images of the heart 

Risk factors for stroke in people with heart enlargement

Identifying the risk factors for stroke associated with an enlarged heart is important for effective prevention.⁷ These risk factors include:

• Hypertension (high blood pressure) and high cholesterol
• Atrial fibrillation³
• Age and family history 
• Sedentary lifestyle and obesity
• Smoking and excessive alcohol use
• Diabetes 

Preventing stroke in people with heart enlargement

To lower the risk of stroke in people with heart enlargement, the primary focus should be on addressing the underlying cause. Using medications that reduce clotting of blood, control blood pressure, and support heart health can significantly help prevent the risk of stroke in individuals with enlarged hearts.

Medications 

Anticoagulants 

Anticoagulants (blood thinners) are prescribed for people at a higher risk of forming blood clots. People with atrial fibrillation (irregular heartbeat) can lower their stroke risk by taking blood thinners regularly. Warfarin is a safe and cost-effective medication for managing atrial fibrillation.⁸ It helps reduce the risk of stroke, especially in people with a moderate to high risk of having a stroke.

Angiotensin-converting enzyme (ACE) inhibitors 

ACE inhibitors help relax blood vessels, which makes it easier for the heart to pump. For some people who cannot tolerate ACE inhibitors, Angiotensin II receptor blockers (ARBs) can be used instead, as it has a similar effect.⁷ 

Antiarrhythmics 

Antiarrhythmics are given to restore the normal heart rhythm in people having atrial fibrillation or other types of arrhythmias.

Beta-blockers 

Beta-blockers are prescribed to slow the heart rate which therefore reduces the strain on the heart and improves heart function.

Lifestyle modifications 

People with an enlarged heart benefit from adopting some lifestyle changes, which may reduce the risk of having a stroke. These include:⁷

• Following a diet which supports heart health
• Reducing salt intake in the diet
• Exercising regularly
• Maintaining optimum levels of blood pressure and cholesterol
• Achieving and maintaining a healthy weight
• Cutting down on alcohol intake
• Quitting smoking 

Surgical interventions 

Heart enlargement in severe cases needs to undergo surgery and may include:⁷

• Implant devices like pacemakers or defibrillators that help the heart maintain a steady rhythm and are usually recommended for people whose heart is not pumping effectively
• Heart valve repair or replacement 

Summary

Heart enlargement occurs when the heart’s size becomes larger due to many factors, like high blood pressure, heart conditions like valve problems, and poor lifestyle choices. This can increase the risk of stroke through several mechanisms. A major contributor is atrial fibrillation (irregular heartbeat), which can allow blood to clot in the heart and travel to the brain. Additionally, if your heart is weak, it may not pump blood effectively, leading to clot formation due to reduced blood flow. Thickened heart walls can also damage blood vessels, increasing the risk of bleeding in the brain. 

People with heart enlargement, especially those with additional risk factors like hypertension, diabetes, and obesity, should be vigilant about their health. Preventive measures should be taken to reduce the risk of stroke and improve heart health, which consists of medications along with some changes in lifestyle like having a healthy diet, keeping blood pressure and cholesterol in control, exercising regularly and avoiding alcohol and smoking.