Atrial fibrillation (AFib) and heart enlargement are connected. AFib can cause an enlarged heart, and heart enlargement due to other causes can lead to episodes of rapid heart rate.

AFib is a rapid, irregular heart rhythm in the upper heart chambers (atria). This type of rhythm does not work well enough to properly circulate the blood, causing it to pool in the heart’s upper chambers.

Pooled blood can clot easily. If a clot moves out of the heart and into circulation, it can block a blood vessel in the brain and cause a stroke. An estimated 15–20% of people who have a stroke also have AFib.

AFib is the most common kind of irregular heart rhythm. It affects an estimated 1–2% of U.S. adults.

This article discusses whether AFib can cause an enlarged heart. It also looks at how AFib can affect the heart in other ways and lists other causes of an enlarged heart.

An anatomically correct heart made from plasticine against a blue background -2.Share on Pinterest
Getty Images

Cardiomegaly refers to enlargement of the heart. There are two types of heart enlargement:

  • Dilation: This occurs when the walls of the heart thin and stretch out, making the heart weaker and larger.
  • Hypertrophy: This refers to a thickening of the heart walls that decreases its efficiency. A person with a heart that works harder for extended periods of time, such as an athlete or and pregnant person, can experience this condition.

Cardiomegaly is usually a symptom of another heart condition, such as cardiomyopathy.

Research from 2019 notes that AFib can cause or exacerbate cardiomyopathy. This is known as atrial fibrillation–mediated cardiomyopathy.

AFib can also lead to ventricular remodeling. The ventricles are the bottom chambers of the heart. Ventricular remodeling can result in the dilation or enlargement of the ventricles and the inability of the heart to pump blood effectively.

In addition, AFib can also worsen existing heart enlargement. Research from 2018 indicates that AFib can be both the cause of and the result of changes to the heart’s anatomy.

AFib interferes with normal heart rhythm by causing the heart’s upper and bottom chambers to become out of sync. This reduces the heart’s ability to circulate blood and can also weaken and enlarge the heart.

In severe cases, AFib can lead to heart failure, which occurs when the heart is unable to pump enough blood to meet the body’s needs.

AFib can also increase a person’s risk of a heart attack, or myocardial infarction (MI). An MI is when cells in the heart muscle die because of insufficient blood flow.

A 2017 review of 15 studies found a link between AFib and subsequent MI in people without coronary heart disease.

Cardiomegaly has causes other than AFib.

They include:

The outlook for a person living with an enlarged heart can depend on factors such as:

  • heart size
  • co-occurring conditions
  • treatment effectiveness

Treating any underlying conditions can help a person with cardiomegaly manage their symptoms. It can also prevent new or worsening complications.

Treatment may include:

  • lifestyle changes
  • medication
  • surgery

Conversely, untreated cardiomegaly can worsen, increasing the risk of complications such as cardiac arrest and stroke.

Life expectancy

A person’s life expectancy with heart enlargement can depend on factors such as the severity of cardiomegaly and co-occurring conditions.

For example, when heart failure co-occurs with heart enlargement, the estimated mortality rate is 1 year for 30% of people and 5 years for 50% of people.

The cause of heart enlargement may also affect the outcome.

Hypertrophic cardiomyopathy (HCM) is a condition in which the left ventricle muscle becomes too thick to effectively pump blood. HCM can lead to heart enlargement.

In most cases, people with HCM can have a good long-term outcome and typical life expectancy. Healthcare professionals may recommend routine checkups and implementing lifestyle adjustments to prevent complications.

Dilated cardiomyopathy (DCM) is another cause of an enlarged heart. It affects the ventricles and can lead to heart failure. DCM has a mortality rate of 50% within 5 years.

However, early and successful treatment of cardiomegaly and its underlying condition can mean that mild heart enlargement has minimal impact on life expectancy.

It is important for people to speak with a healthcare professional to understand the cause of their heart enlargement and reduce their risk of complications.

The Centers for Disease Control and Prevention (CDC) estimates that heart failure affects about 6.2 million U.S. adults.

AFib can lead to heart failure. This is because the rapid and irregular heart rhythm of AFib affects the heart’s ability to adequately pump blood, and it may result in inadequate circulation in the body.

Heart failure symptoms include:

  • shortness of breath
  • edema, or the buildup of fluid in the body’s tissues
  • persistent wheezing or coughing
  • fatigue
  • nausea
  • lack of appetite
  • fast heart rate
  • cognitive impairment, such as confusion

AFib can both cause and result from cardiomegaly. It can also cause other heart issues like heart failure.

AFib isn’t the only cause of heart enlargement. Others include heart and lung disease, infections, and toxicity-related heart damage.

The outlook and life expectancy for a person with cardiomegaly can vary based on the severity of the condition and the presence of other health conditions. Treatment of underlying conditions can stabilize cardiomegaly symptoms and prevent new complications.

Symptoms of heart failure due to AFib include shortness of breath, edema, and fatigue.