Overview 

A heart attack (myocardial infarction or MI) is a medical emergency that happens when blood flow to the heart muscle is blocked. Most often, this is caused by a build-up of fatty deposits in the arteries, but other conditions, such as coronary artery disease, can also play a role.

An enlarged heart (cardiomegaly) is not a disease itself, but a sign of another problem that is making the heart work harder than usual. Over time, this extra strain can increase the risk of complications, including heart attacks and, in some cases, heart failure. People with an enlarged heart who experience a heart attack often need specially tailored treatment to help protect their heart and reduce the risk of further problems.

What is a myocardial infarction?

A heart attack (myocardial infarction) happens when the coronary arteries – the blood vessels that supply the heart – cannot deliver enough oxygen-rich blood.¹ This is usually because of a blockage. Without oxygen, part of the heart muscle can become permanently damaged, and in severe cases, it can be life-threatening.

Risk factors  

Several factors can make a heart attack more likely. These include:

• Smoking
• High blood pressure (hypertension)
• An unhealthy diet
• Lack of regular exercise
• Getting older (men over 45 and women over 50 are at higher risk)
• Drinking too much alcohol
• A family history of heart disease
• Conditions such as diabetes or high cholesterol
• Coronary artery disease, which is the most common cause

Heart enlargement

An enlarged heart (cardiomegaly) is not an illness on its own but a sign that the heart is under strain. This may happen because the heart muscle becomes thickened or stretched.²

An enlarged heart (cardiomegaly) is not an illness on its own but a sign that the heart is under strain. This may happen because the heart muscle becomes thickened or stretched.

Possible causes include:

• High blood pressure (hypertension)
• Heart valve disease
• Inflammation of the heart muscle (myocarditis)
• Coronary heart disease
• Damage from a previous heart attack
• Obesity
• Thyroid problems
• Older age
• Anaemia
• Pregnancy
• Lifestyle factors such as smoking, drinking too much alcohol, or a lack of exercise

Treatment for an enlarged heart depends on the underlying cause. People with cardiomegaly need regular check-ups, as they are at a higher risk of heart failure if the condition is not managed properly.

Diagnosis of a heart attack 

A heart attack often begins with a heavy, squeezing pain in the chest. This pain may spread to the arms, shoulders, neck, back, or jaw. Sometimes, it can feel like severe indigestion or heartburn, which is why it can be mistaken for less serious problems.⁶

Other common symptoms include:

• Chest pain or tightness
• Shortness of breath
• Feeling sick (nausea)
• Sweating
• Feeling very anxious or dizzy
• A pounding or irregular heartbeat (palpitations)
• Difficulty sleeping, often because of discomfort.

If you think you or someone else may be having a heart attack, call 999 straight away.

Relationship between heart enlargement and MI

Having an enlarged heart does not directly cause a heart attack. However, the conditions that lead to an enlarged heart – such as high blood pressure or heart valve problems – can raise the risk of one happening. This is why people with cardiomegaly need careful monitoring and management.³

​​Treatment for cardiomegaly may include:

• Lifestyle changes, such as reduced salt intake and alcohol consumption 
• Medications, such as antiarrhythmics to maintain a regular heart rhythm or anticoagulants to reduce the risk of blood clots
• In rare cases, surgery may be necessary to repair a damaged heart valve or implant a pacemaker that helps maintain a steady heart rhythm⁴

Treatment and management 

Because people with an enlarged heart are more likely to have complications after a heart attack, treatment needs to be carefully tailored to them.

Quick treatment is vital to limit permanent damage to the heart. This may include:

• Oxygen therapy – given through a mask or tube if someone is struggling to breathe, helping to reduce strain on the heart.
• Medicines – such as aspirin or other drugs that stop blood clots from forming and improve blood flow. Nitroglycerin may be used to open up blood vessels, and in some cases, morphine can help ease severe pain.

The main goal of treatment is to quickly unblock the arteries and restore blood flow. This can be done in two main ways:

• Percutaneous Coronary Intervention (PCI) – often called angioplasty. A thin tube (catheter) is guided into the blocked artery, where a small balloon is inflated to clear the blockage. A stent (a small mesh tube) is usually left in place to keep the artery open.
• Coronary Artery Bypass Graft (CABG) – used if several arteries are blocked. A healthy blood vessel, usually taken from the leg, chest, or arm, is used to bypass the blocked section and restore blood flow.⁷

After a myocardial infarction

After a heart attack, people with an enlarged heart need ongoing care to reduce the risk of complications such as heart failure.

Medicines are often an important part of this care:

• ACE inhibitors – help relax blood vessels, lowering blood pressure and reducing strain on the heart
• Beta-blockers – slow the heart rate and improve blood flow
• Aldosterone antagonists can prevent scarring of the heart muscle, which would otherwise make the enlarged heart work even harder⁸

This is usually achieved with medications such as ACE inhibitors, which lower blood pressure by relaxing the blood vessels. Beta-blockers may be prescribed to slow the heart rate, reduce blood pressure and improve circulation. Typically, aldosterone antagonists are administered to prevent scarring of the heart tissue, which may exacerbate the symptoms of cardiomegaly. 

Ongoing care is just as important as emergency treatment. This usually includes:

• Lifestyle changes – eating a healthy diet, cutting down on salt and alcohol, and staying physically active in a safe way
• Regular monitoring – follow-up appointments with a heart specialist (cardiologist) to check progress and adjust medicines if needed
• Cardiac rehabilitation – a structured programme that combines gentle exercise, education, and support to help patients regain strength and confidence while protecting their heart³

Long-term effects and potential complications 

People who have had a heart attack and also have an enlarged heart are at greater risk of long-term problems. These may include:

• Heart failure – when the heart struggles to pump blood effectively
• Repeat heart attacks – blockages may return, especially if risk factors aren’t controlled
• Arrhythmias – irregular heart rhythms, which can sometimes be dangerous

To reduce these risks, doctors may recommend an implantable cardioverter defibrillator (ICD). This is a small device fitted under the skin of the chest. It constantly monitors the heart’s rhythm and can deliver a small electric shock if a dangerous rhythm is detected, restoring the heartbeat to normal.⁵

For those who do not need or want surgery, medicines can help. One example is digoxin, which helps the heart pump more strongly and prevents fluid from building up in the body. This can improve circulation and ease symptoms like swelling and breathlessness.

FAQs

Are people with an enlarged heart more likely to suffer from a heart attack?

Yes, but not directly because of the enlarged heart itself. Instead, the conditions that cause the heart to enlarge — such as high blood pressure, coronary artery disease, or valve problems — also increase the risk of a heart attack. Managing these conditions with treatment and lifestyle changes can significantly reduce the risk.

Can an enlarged heart go back to its normal size?

In some cases, yes. If the underlying cause — such as high blood pressure or a thyroid problem — is treated early, the heart can return closer to its normal size and function. However, if the heart muscle has been badly damaged, it may not fully return to normal, but treatment can still improve symptoms and quality of life.

How can I lower my risk of another heart attack if I have an enlarged heart?

You can reduce your risk by:

• Take your prescribed medications regularly
• Following a heart-healthy diet with less salt and processed food
• Keeping active with safe, regular exercise is recommended by your doctor
• Avoiding smoking and cutting down on alcohol
• Attending regular check-ups and monitoring your condition

If someone has an enlarged heart and suffers a heart attack, treatment needs to be carefully tailored to reduce the risk of further complications. The first priority is always to restore blood flow to the heart quickly, which helps limit permanent damage.

Afterwards, long-term care focuses on preventing further heart problems. This usually involves medications, lifestyle changes, and regular follow-up appointments with a specialist. In some cases, procedures such as stents, bypass surgery, or even devices like pacemakers may be needed to support the heart.

If you ever experience sudden chest pain, breathlessness, or symptoms that may be a heart attack, call 999 immediately. Quick treatment saves lives.

Summary

A heart attack (myocardial infarction) occurs when blood flow to the heart is blocked, causing damage to the heart muscle. An enlarged heart (cardiomegaly) is not a disease itself but a sign of strain, often linked to conditions like high blood pressure, coronary artery disease, or valve problems, which also increase heart attack risk.

Treatment for a heart attack in people with an enlarged heart must be carefully tailored. Emergency care focuses on quickly restoring blood flow using medicines (e.g., aspirin, nitroglycerin), oxygen therapy, and procedures such as angioplasty with stent placement or coronary bypass surgery. After recovery, ongoing management includes medications (ACE inhibitors, beta-blockers, aldosterone antagonists), lifestyle changes, cardiac rehabilitation, and regular follow-ups.

Because cardiomegaly increases the risk of complications like heart failure, arrhythmias, or repeat heart attacks, some patients may also need devices such as pacemakers or implantable cardioverter defibrillators (ICDs). Early treatment of underlying causes and healthy lifestyle habits are key to reducing long-term risks.