What Is Right Atrial Enlargement?

Introduction

The heart, a vital organ responsible for sustaining the human body, is composed of four distinct chambers, each serving a unique purpose. The right atrium, positioned in the upper-right part of the heart, is where deoxygenated blood enters the heart before being sent to another heart chamber and to the lungs. However, sometimes, the right atrium can increase in size, leading to a condition known as Right Atrial Enlargement (RAE). RAE can manifest with symptoms like fatigue, shortness of breath, edema, and arrhythmias, and in some cases, it might even remain asymptomatic.¹

The condition can have a plethora of underlying causes such as high blood pressure, tricuspid valve diseases, cardiac conditions, and chronic lung diseases.² RAE may also be congenital (present at birth) or idiopathic (spontaneous) meaning that there is no underlying health condition causing it.^3,4 If caught early, the prognosis for RAE is generally positive, however if left untreated, can become very serious, with a mortality rate of around 5%.⁵

Anatomy and Function of the Right Atrium

Overview of the Heart's Structure

The heart is a vital organ responsible for pumping oxygenated blood to all the body's tissues and organs, which provides them the oxygen they need to function.⁶ The heart consists of four distinct chambers (parts), each with their own function, which are outlined here;

• Right Atrium: This is the top-right chamber of the heart. It receives deoxygenated blood returning from the body via the superior and inferior vena cava, the two largest veins in your body
• Right Ventricle: Located below the right atrium, the right ventricle receives deoxygenated blood from the right atrium and pumps it to the lungs where it takes in the oxygen we breathe.
• Left Atrium: The top-left chamber of the heart. It receives oxygenated blood from the lungs via the pulmonary veins.
• Left Ventricle: Positioned below the left atrium, the left ventricle receives oxygenated blood from the left atrium and forcefully propels it throughout the body through the aorta artery.6

The Importance of the Right Atrium

The right atrium is critical to the circulation of blood around the body as it is the point of entry for deoxygenated blood to the heart. The tricuspid valve separates the right atrium and the right ventricle, and is opened through the force generated by the right atrium's contraction. The blood can then flow through into the right ventricle and be sent off to the lungs for oxygenation. In a healthy heart, it contracts and relaxes rhythmically; the right atrium will contract at the same time as the left atrium, and once the blood has been received in both ventricles, they too will contract in unison, creating our heartbeat.

The right atrium is generally smaller than the left atrium, with the size of the right atrium varying due to height, age, and sex. Additionally, body-mass index, coronary artery disease, and atrial fibrillation have all been linked to right atrium size, and could potentially be a cause of right atrial enlargement.⁷

Causes of Right Atrial Enlargement

High Blood Pressure

High blood pressure, medically referred to as pulmonary hypertension, is a primary factor contributing to right atrial enlargement. Pulmonary hypertension arises from an increased pressure in the pulmonary arteries connecting to the right ventricle, which sends blood from the heart to the lungs.⁸ When pulmonary hypertension occurs the right atrium has to work harder to push blood into the right ventricle, which causes its enlargement over time.

Tricuspid Valve Disease

As we already mentioned, the tricuspid valve separates the right atrium and right ventricle and moderates the flow of blood from the atrium to ventricle. Diseases associated with the tricuspid valve can distort the pressure in the atrium and lead to right atrial enlargement.

One such condition is tricuspid regurgitation, where the tricuspid valve does not close properly, akin to a loose lid, so the blood can leak back into the atrium.⁹ Another condition, tricuspid stenosis, involves the narrowing of the valve, making it difficult for blood to flow through, increasing the pressure in the atrium.¹⁰

Cardiac Conditions

Congenital heart defects present at birth affect the structure and function of the heart. Some individuals are born with heart issues that affect the right atrium's size and function leading to an enlarged right atrium.

Left-sided heart failure can cause a backup of blood into the right atrium, increasing its workload, leading to RAE.⁷

Arrhythmias (irregular heart rhythms), such as atrial fibrillation, can disrupt the flow of blood through the heart, potentially contributing to RAE.¹

Chronic Lung Diseases

Chronic lung diseases, particularly Chronic Obstructive Pulmonary Disease (COPD), can lead to increased pressure in the blood vessels of the lung.¹¹ This can then lead to the increase in size of the right ventricle and issues with the heartbeat, eventually leading to right atrial enlargement.

Idiopathic Right Atrial Enlargement

An idiopathic disease means a disease that occurs spontaneously or from an unknown cause, this means that RAE can occur without any of the underlying diseases outlined above. This type of RAE can be asymptomatic, where the patient will show no signs of the disease. In some cases, idiopathic RAE can cause arrhythmia or shortness of breath, but there have been instances where the disease can turn life-threatening.⁵ Because some symptoms of idiopathic RAE, such as arrhythmias, can also be the cause of right atrial enlargement, it is often difficult to narrow down the route cause of RAE, and oftentimes it is treated symptomatically.

Clinical Presentation and Symptoms

Depending on the underlying cause and degree of atrial enlargement, the symptoms of RAE can vary greatly. Additionally it is possible for idiopathic RAE not to show any symptoms at all. The most common symptoms of RAE include:

• Fatigue
• Shortness of Breath⁵
• Edema (swelling caused by the buildup of fluids in the body)¹²
• Palpitations⁵

Diagnosis of RAE

Thankfully, the heart has been intimately studied, and there is now lots of equipment specifically used to diagnose problems with the heart. For instance, electrocardiography (ECG) can be used to record the electrical signals of the heart. Certain abnormalities can be a tell-tale sign of right atrial enlargement.¹³

Similarly, echocardiography, a type of ultrasound scan, can be used to produce a clear image of the heart's size and structure, allowing healthcare professionals to identify a potential enlargement of the right atrium.¹⁴

A chest X-ray may also be used to provide a general overview of the heart’s size and shape, however, it may not be as precise as an echocardiograph.

Complications Associated with RAE

A number of complications are associated with RAE, many of which can be treated as they arise, however these complications can skew quite severe which may signify the need for surgical intervention. 

Atrial fibrillation is the irregular and often quickened beating of the heart.¹⁵ This is caused by asynchronicity in the heart, due the right atrial enlargement, and can lead to the pooling of blood in the heart. The stagnant blood flow in the enlarged right atrium can lead to the formation of blood clots (thrombi). If these clots dislodge and travel through the bloodstream, they can cause thromboembolic events, such as pulmonary embolism or stroke.¹⁶ RAE can also contribute to heart failure by reducing the heart's overall efficiency in pumping blood.¹ 

Complications with the heart are often complex and can have a knock-on effect causing other issues. As such it is essential for individuals with symptoms suggestive of RAE to seek medical advice and diagnosis promptly. Early detection and management can help prevent or mitigate the potential complications associated with this condition.

Management and Treatment

The management of RAE is highly individualised, with treatment plans depending on the underlying cause, the patient's overall health, and the severity of symptoms. Regular follow-up with a healthcare provider is essential to monitor progress and adjust the treatment plan as needed. Early intervention and diligent management can help improve heart function, alleviate symptoms, and reduce the risk of complications associated with RAE.

Medications

There are a multitude of different drugs that can be prescribed to patients to help alleviate symptoms caused by RAE, however, these drugs will not cure RAE itself, this is called symptomatic care.⁵

Diuretics may be prescribed in the event of edema and shortness of breath to help reduce fluid build up. The removal of fluid from the blood will also help reduce blood pressure.

Anticoagulants may be used where there is an increased risk of thromboembolic events (issues caused by blood clots) due to atrial fibrillation. Warfarin is a common anticoagulant which is commonly referred to as a ‘blood-thinner’.

Other drugs may be prescribed to target blood pressure such as ACE-inhibitors or calcium channel blockers.

Lifestyle Modifications

Patients with RAE may be advised to make certain lifestyle modifications to support their heart health. Diet and exercise, weight management, fluid restriction, and giving up smoking can all help alleviate strain on the heart and support overall health.

Surgical Interventions

In more severe cases, surgical interventions may be necessary to address RAE directly.¹⁷ Surgery can take many forms and ultimately depends on the underlying issue and current symptoms of the patient. In the case of tricuspid valve disease, the tricuspid valve can be repaired or replaced, alleviating regurgitation or stenosis and reducing RAE. 

For treatment of atrial fibrillation, a catheter ablation may be considered to normalise the heartbeat.¹⁸ Thankfully, this is a minimally invasive treatment option.

Patients with congenital heart defects (present at birth) which contributed to RAE may undergo corrective surgeries, or in extreme cases, a heart transplant may be an option.¹⁹

Prognosis

The prognosis and outcomes of Right Atrial Enlargement (RAE) depend on several factors, including the underlying cause, the extent of atrial enlargement, and the patient's overall health. Early diagnosis and effective management of symptoms and complications are essential for improving outcomes and cardiac health. It's important for individuals with RAE to work closely with their healthcare team to develop a treatment plan and to follow up as recommended to optimise their prognosis.

The prognosis of Rae can therefore range from simply managing symptoms with medication with the disease having little impact on overall health to serious heart damage resulting in surgery. In the worst cases of RAE, the disease can be fatal, with a mortality rate of around 5%.²

Summary

Right Atrial Enlargement (RAE) is a condition where the right atrium of the heart is unusually enlarged. It is typically diagnosed through echocardiography and may present with symptoms like fatigue, shortness of breath, edema, and palpitations. Underlying causes include high blood pressure, tricuspid valve diseases, cardiac conditions, and chronic lung diseases, but it may be present at birth, or occur spontaneously. 

The management varies based on the cause and may involve treating underlying conditions via medications like diuretics and anticoagulants, lifestyle changes, or surgical interventions. RAE can lead to complications like atrial fibrillation and thromboembolic events and in extreme cases be fatal. However, if caught early and with effective management, the disease can have a favourable prognosis.