An enlarged heart (cardiomegaly) is usually not a disease by itself but a sign that the heart has been overworked or damaged by another condition, such as high blood pressure or coronary artery disease. It can also be caused by heart muscle disease, valve problems, lung-related high blood pressure, infections, or certain systemic illnesses.

What an “enlarged heart” means

An enlarged heart means the heart’s chambers or muscle walls have increased in size, often because the heart has been forced to pump harder than normal for a long time. This can make the heart weaker over time and less able to pump blood efficiently, leading to symptoms like shortness of breath, fatigue, or swelling in the legs.

Major medical causes

The most common causes of an enlarged heart are long-standing high blood pressure and ischemic (coronary) heart disease. These conditions make the heart push against higher resistance or work with reduced blood supply, which causes thickening or stretching of the heart muscle.

Key causes include:

  • High blood pressure (hypertension)
  • Coronary artery disease and prior heart attack
  • Cardiomyopathy (diseases of the heart muscle, including genetic forms)
  • Heart valve disease (leaky or narrowed valves)
  • Pulmonary hypertension (high pressure in lung arteries)
  • Long-standing fast heart rhythms

Other conditions that can enlarge the heart

Many non-artery causes can also lead to an enlarged heart over time.

Examples include:

  • Infections of the heart muscle (myocarditis), including viral and HIV-related
  • Thyroid disorders (both overactive and underactive gland)
  • Kidney disease and fluid overload
  • Severe anemia or chronic lung disease
  • Excess alcohol or cocaine use
  • Pregnancy-related heart weakness (peripartum cardiomyopathy)
  • Genetic or inherited heart conditions
  • Excess iron or certain infiltrative diseases (such as amyloidosis)

Lifestyle and risk factors

Several lifestyle factors increase the risk of developing the conditions that enlarge the heart.

Important contributors include:

  • Obesity and a sedentary lifestyle
  • High cholesterol and unhealthy diet
  • Smoking and other tobacco use
  • Heavy, long-term alcohol use or recreational drugs (especially cocaine)
  • Older age and a family history of heart disease

When to worry and what to do

An enlarged heart is taken seriously because it can lead to heart failure, dangerous heart rhythms, or blood clots if not treated. Anyone with chest pain, unexplained shortness of breath, fainting, or sudden swelling in legs or abdomen should seek urgent medical evaluation rather than waiting.

This explanation is general information, not personal medical advice. If you or someone you know has been told they have an enlarged heart, a cardiologist can determine the specific cause and treatment plan.