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The term arrhythmia describes an irregular and often rapid heart rate. Atrial fibrillation (AF) is a common cardiac arrhythmia resulting from disorganised electrical signals in the atria, the heart’s upper chamber. The irregular rhythm reduces the heart’s efficiency; this can lead to symptoms such as fatigue, palpitations and shortness of breath, and also increases the risk of stroke and heart failure.^1,2 Cardiomegaly, or heart enlargement, refers to an increase in the size of the heart, typically resulting from conditions that overwork the heart, such as high blood pressure (hypertension) or heart valve disease. This enlargement can compromise the heart's ability to pump blood, worsen symptoms, and raises the risk of complications.³

Understanding the relationship between AF and cardiomegaly is crucial because each condition can worsen the other, creating a cycle that increases the likelihood of serious complications. For instance, the presence of AF in a patient with an enlarged heart can lead to more severe symptoms, a greater risk of stroke, and an increased chance of heart failure due to the cumulative stress on the heart.⁴

Additionally, treatment strategies for AF may need modification when cardiomegaly is present, as enlarged heart structures can affect the success of interventions such as rhythm control or ablation procedures (treatments that destroy small areas of heart tissue causing abnormal rhythms).⁵

By studying how these two conditions interact, healthcare providers can develop more effective and personalised treatment plans that mitigate risks and improve long-term outcomes for affected patients.

What is Atrial fibrillation?

Atrial fibrillation is an irregular and often rapid heart rhythm that starts due to abnormal electrical activity in the atria (the upper heart chambers). The disorganised electrical signals cause the atria to quiver (twitch instead of beating properly), which reduces the heart's efficiency and increases the risk of blood clots, stroke and heart failure.¹

The development of AF is typically linked to a variety of risk factors, including high blood pressure, coronary artery disease, heart valve issues, and advancing age. These conditions can cause structural and electrical changes (remodelling) in the heart, making arrhythmias more likely.^6,7 Other factors, such as obesity, diabetes, and heavy alcohol intake, can also raise the risk of developing AF.⁸

People with AF may experience a range of symptoms, including palpitations (a fast or irregular heartbeat), shortness of breath, fatigue, dizziness, and sometimes chest pain. However, in some cases, AF may not cause noticeable symptoms, and people may be unaware of the condition until a routine check-up or screening.⁹ Recognising these symptoms early is essential for timely treatment and reducing the risk of complications.

Enlarged heart (Cardiomegaly)

Cardiomegaly, commonly referred to as heart enlargement, is a condition where the heart increases in size due to factors that place extra strain on its function, such as high blood pressure, heart valve disease, and cardiomyopathy.¹⁰ Cardiomegaly can be classified into two main types: dilated cardiomegaly, where the heart’s chambers expand, and hypertrophic cardiomegaly, where the heart muscle thickens (becomes enlarged). Both types change the heart’s structure and reduce its ability to pump blood effectively.¹¹

High blood pressure is a common cause of cardiomegaly, as the heart must work harder to pump blood against increased resistance in the blood vessels. Heart valve diseases, such as aortic stenosis or mitral regurgitation, also contribute by placing strain on the heart through disrupted blood flow. Cardiomyopathy, a heart muscle disease, may cause the heart to enlarge as it tries to compensate for reduced function.¹² The condition can disrupt normal blood flow, leading to symptoms like shortness of breath, fatigue, and oedema (fluid retention or swelling). It also increases the risk of heart failure.¹³

How are AF and heart enlargement connected?

Atrial fibrillation (AF) and cardiomegaly have a two-way relationship that makes each condition worse over time. AF can contribute to heart enlargement by increasing the workload on the heart. During AF, the heart’s irregular rhythm reduces its efficiency. This causes the ventricles to work harder to pump blood, which leads to changes in the heart’s structure and enlargement over time.¹⁴

Conversely, cardiomegaly increases the risk of developing AF, as changes in the heart’s size and electrical signals can promote the onset of arrhythmias. Enlarged atrial chambers, in particular, are prone to AF due to increased tissue surface area and changes in how electrical signals travel through the heart.^15,16 This two-way relationship can create a vicious cycle. AF worsens cardiomegaly, and an enlarged heart further predisposes a patient to AF, escalating the likelihood of heart failure, stroke, and other complications.¹⁷

Symptoms 

Patients with both atrial fibrillation (AF) and cardiomegaly experience more severe symptoms than those with just one of these conditions. The combination of an irregular heart rhythm and an enlarged heart can worsen symptoms such as shortness of breath, fatigue, and dizziness. This happens because the heart struggles to pump blood effectively around the body.¹⁸

Impact on quality of life

All the intensified symptoms can significantly limit patients' ability to engage in daily activities, contributing to a decline in physical ability, function, and independence.¹⁹ Moreover, having these symptoms regularly often leads to mental health challenges, including stress and anxiety. Many patients report a reduced quality of life due to the unpredictable and exhausting nature of AF episodes, along with the physical limits caused by cardiomegaly.¹⁰ This overall effect can cause emotional distress and may even lead to depression in some people.¹⁰

Associated complications

Patients with both AF and cardiomegaly are at an elevated risk for serious complications. One of the primary risks is stroke; the irregular heart rhythm in AF causes blood to pool in the atria, increasing the likelihood of clot formation. If a clot travels to the brain, it can cause an ischemic stroke, which is potentially life-threatening.⁷ In fact, patients with AF are five times more likely to experience a stroke than those without the condition.⁷

The inefficiency of the heart in patients with both AF and cardiomegaly also raises the likelihood of heart failure. Cardiomegaly already compromises cardiac output, and AF further disrupts the heart’s ability to pump blood effectively, leading to fluid buildup, congestion, and worsening heart failure.²⁰ This combination of AF and cardiomegaly is associated with increased rates of hospitalisation and higher mortality, underscoring the need for effective management to prevent severe outcomes.²⁰

Challenges in the management

Managing atrial fibrillation (AF) in patients with cardiomegaly presents unique challenges. Enlarged hearts can complicate treatment. Structural changes often make it harder to achieve stable heart rhythms and increase the risk of recurrent AF episodes.²¹ Medications like beta-blockers and rhythm control drugs, which are typically used to manage AF, may be less effective in patients with cardiomegaly because their bodies process the drugs differently or may not tolerate them well.

Additionally, managing blood thinning (anticoagulation) control can be difficult, as these patients have a higher risk of clot formation and bleeding.²² Common treatments for AF include anticoagulants, beta-blockers, and antiarrhythmic medications. Anticoagulants, such as warfarin or direct oral anticoagulants, are vital for reducing stroke risk in AF patients.

However, patients with cardiomegaly may need close monitoring to balance stroke prevention with the risk of bleeding.¹ Beta-blockers help control heart rate, while rhythm control medications aim to restore a normal rhythm. Unfortunately, enlarged heart structures often reduce the effectiveness of these drugs, which may mean higher doses or combination therapies that may increase the chance of side effects.¹

For patients with persistent or refractory AF, procedures like catheter ablation or surgical interventions may be considered. Catheter ablation, which targets and destroys tissue causing abnormal electrical signals, has shown some success in people with cardiomegaly, although it may be less effective due to the larger atrial tissue area involved.²³

Surgical procedures, such as the Maze procedure, can be effective in certain cases but are generally reserved for patients who do not respond to other therapies.²³ Lifestyle changes, including weight management, dietary adjustments, and alcohol reduction, are also crucial as they can help relieve AF symptoms and support heart function.²⁴

Summary 

Atrial fibrillation has a major impact on patients with heart enlargement, often worsening symptoms, reducing quality of life, and increasing the risk of complications like stroke and heart failure. The two-way relationship between AF and an enlarged heart makes treatment more difficult, as each condition can worsen the other. It can push patients towards other conditions such as stress, anxiety, and patients can be the victims of depression. Besides, it takes a toll on physical ability, and patients find it difficult to perform the activities of daily living. Early diagnosis, regular check-ups, and personalised treatment plans are key to managing both conditions effectively. By tailoring therapies to individual patient needs and focusing on prevention, healthcare providers can improve long-term outcomes and quality of life for patients dealing with this challenging combination.