What Is the Right Atrium?

The right atrium is one of the heart's upper chambers that plays a role in blood circulation. It collects deoxygenated blood and directs it on a pathway to get oxygen from the lungs. Problems with the right atrium can occur from birth or due to problems with the heart valves or muscles. They can be associated with arrhythmias, blood clots, and heart failure.

This article will discuss the right atrium's structure and function, and the various problems and complications that can occur related to the right atrium.

Heart Structure and Blood Flow

The heart is a muscular pump with four chambers: two upper chambers called atria, and two lower chambers called ventricles. These chambers are responsible for the blood's flow through the body. These atria are thin-walled chambers that passively collect blood, while the ventricles are thicker-walled chambers that pump blood to the lungs and body.

The right atrium collects deoxygenated blood from the body and directs it to the right ventricle, where it is then pumped to the lungs to get oxygen. The oxygenated blood comes from the lungs and flows back to the heart via the left atrium, where it's directed to the left ventricle. From there, it is pumped to the body.

Right Atrium Anatomy

The right atrium contains parts of the cardiovascular system that are key to overall health.

Structure

The right atrium is a thin-walled chamber that sits at the top right side of the heart. While it's shape is mostly round, it also has an extension known as the right atrial appendage. Within the walls of the right atrium is the sinus node, an important part of the heart's electrical system that generates the heart beat signal.

Location

The right atrium sits at the top right side of the heart. Two large veins, the inferior vena cava and superior vena cava, empty into the right atrium. The superior vena cava brings deoxygenated blood from the upper body, while the inferior vena cava brings deoxygenated blood from the lower body. Another vein, known as the coronary sinus, carries blood from the heart muscle to the right atrium. The right atrium is separated from the right ventricle by the tricuspid valve, which opens to allow blood to flow into the right ventricle.

The atrial septum separates the right and left atrium, and normally there is complete separation so that blood does not mix from the right and left atrium. However, in as many as one in four people, there is a connection left over from fetal development known as a patent foramen ovale.

Right Atrium Function

The right atrium has a function in both the flow of blood through the heart, as well as in the heart's electrical system. In regards to blood flow, deoxygenated blood from the superior and inferior vena cava and the coronary sinus collect in the right atrium. From there, blood flows across the tricuspid valve into the right ventricle, where it is sent to collect oxygen in the lungs.

The electrical system of the heart is a complex system of specialized tissue that creates a signal for the heart to beat. It starts in the sinus node, located in the right atrium, and travels through both atria to stimulate contraction. It then goes to the atrioventricular node and travels toward the ventricles to stimulate their contraction. In this way, the heart has a timed contraction of atria, then ventricles that allow for the efficient flow of blood.

Clinical Significance of the Right Atrium

Various conditions can affect the right atrium. These may be congenital, meaning present from birth, or acquired, meaning developed later in life. They can affect the structure and function of the atrium, resulting in impedance of blood flow out of the right atrium, increased risk of clot formation, stroke, and heart failure.

Structural Problems

Congenital (present from birth) conditions of the right atrium include:

• Patent foramen ovale (PFO) is the persistence of a fetal connection between the left and right atrium that has been implicated in stroke and migraine headaches.
• Atrial septal defect (ASD) is an abnormal connection between the left and right atrium that can lead to mixing of oxygenated and deoxygenated blood. Depending on the size it can lead to heart failure, arrhythmias, stroke, and pulmonary hypertension and may need to be closed with surgery or catheter-based intervention.
  
• Atrial septal aneurysm is an excess of the tissue separating the right and left atrium that bulges into the right and/or left atrium. It is often associated with PFO and may be associated with an increased risk of stroke.
• Ebstein's anomaly is a congenital condition affecting the entire right side of the heart, with a small ventricle, large atrium, and malformed tricuspid valve that may require surgery
  

Acquired conditions of the right atrium include:

• Right atrial enlargement from various types of heart or lung disease.
• Tumors, such as atrial myxoma or metastatic tumors from the breast, lung, or skin.
• Blood clot in the right atrium.
• Infection, or endocarditis.

Arrhythmias

Various arrhythmias (irregular heartbeats) can occur due to problems with the electrical tissue within the right atrium, including:

• Atrial fibrillation
• Atrial flutter
• Accessory pathways that may lead to atrioventricular reentrant tachycardia (AVRT)

Summary

The right atrium is one of the four chambers of the heart that collects deoxygenated blood and directs it ultimately to the lungs to receive oxygen. Problems with the right atrium can occur from birth or be acquired later in life, usually due to other problems with the heart and lungs. Conditions affecting the right atrium can lead to arrhythmias and increase the risk of blood clots, and stroke.