The coronary sinus (CS) refers to a collection of veins that join together to form a large blood vessel. This vein is located between the left atrium and the left ventricle of the heart.
The heart is a vital organ and the central component of the circulatory system. To help pump blood around the body, it uses a network of arteries and veins. The CS is responsible for delivering deoxygenated blood to the right atrium and plays a vital role in life saving heart treatments.
A collection of coronary veins join to form the CS. This large vein receives blood from the myocardium, which is a thick layer of muscle in the heart. It then passes this venous blood into the right atrium. The anatomical location of the CS often serves as a landmark for surgeons when performing cardiac surgery.
In this article, we will discuss the anatomy and function of the CS, as well as the clinical role of the CS.
The CS is a large coronary vein that measures between 3–5 centimeters (cm) in length and 1–2 cm in diameter. This large venous structure is responsible for draining the majority of deoxygenated blood into the right atrium.
Many tributaries, or smaller veins, feed into and form the CS, though the exact anatomy may differ among individuals.
Some veins that may feed into and form the CS
- great cardiac vein
- oblique vein of the left atrium
- posterior vein of the left ventricle
- middle cardiac vein
- small cardiac vein
The location of the CS is toward the posterior, or rear, of the heart, between the left atrium and the left ventricle.
Some may describe the starting point of the CS as where the great cardiac vein and the oblique vein of the left atrium meet. Others may describe the Vieussens valve as the origin of the CS.
The large blood vessel then continues between the left atrium and left ventricle, running along the interventricular groove, and finally empties into the right atrium.
The CS is responsible for returning the bulk of the heart’s deoxygenated blood, which is also known as cardiac venous blood. It carries this blood from most of the blood vessels of the heart muscle and wall.
The CS is responsible for returning approximately
There are many different anatomical variations of the CS ranging from size, the number of smaller veins that connect to it, and the shape, or form, of the valves that surround it.
Most anatomical variations are harmless, although some may present clinical implications for cardiac procedures. The presence of irregular valves in the CS may hinder some cardiac intervention techniques.
Some anatomical variations that could lead to further health complications include:
- Persistent left superior vena cava (PLSVC): The large vein, known as the superior vena cava, usually drains into the right atrium. PLSVC occurs when this vein appears on the left side of the heart instead of the right. The blood then drains directly into the CS. PLSVC affects 0.2–3% of the general population and is usually asymptomatic. However, it can lead to various heart conditions, such as arrhythmias and cyanosis.
- Unroofed CS syndrome: This is a rare type of atrial septal problem that occurs when a section, or the whole of the roof of the CS, is missing. This can result in communication problems between the CS and the left atrium. Early diagnosis and treatment of unroofed CS syndrome are vital, as it can lead to right to left cardiac shunt, which can cause hypoxia, blood clots, and heart failure.
- Coronary artery fistulas (CAFs) to the CS: This refers to connection problems between a coronary artery and the CS. CAFs are usually asymptomatic and are often detected by chance during heart imaging. However, symptoms and complications can become more problematic later in life, and it can lead to heart failure.
Due to the anatomical location of the CS, it can play a significant role in both clinical and surgical heart procedures. Some of these may include:
- Cardiac resynchronization therapy (CRT): The CS provides a vital role in treatment used to regulate a person’s heartbeat, known as CRT. When performing this procedure, a surgeon will place a pacemaker under a person’s skin. There are three leads that originate from the pacemaker. The surgeon will place the left ventricular lead into the CS to stimulate contraction of the left ventricle.
- Electrophysiology studies (EPS): A clinician will use this procedure to diagnose an irregular heartbeat, or arrhythmia. During the procedure, the clinician will place wire electrodes into the CS to help diagnose these conditions.
- Retrograde cardioplegia: This is one way that cardiac surgeons can temporarily stop the heart during complex heart surgery. The location of the CS provides easy access to the blood vessels in the heart, which make the CS an ideal candidate for retrograde cardioplegia. An extremely rare, yet major complication of retrograde cardioplegia, is a rupture of the CS.
- Coronary sinus reduction: A clinician may use this procedure for the treatment of angina. A surgeon places an hourglass-shaped stent inside the CS to create a narrowing. This will increase a person’s blood pressure, helping to redistribute oxygenated blood to the parts of the heart that require it.
The coronary sinus describes a major coronary vein located in the rear section of the heart.
Many smaller cardiac veins connect to it to make it the largest vein of the heart. The main function of the CS is to drain deoxygenated blood from the heart muscle into the right atrium.
The location of the CS makes it an ideal candidate for many surgical procedures concerning the heart, including heart pacemaker surgery.
With the advancement in interventional heart procedures, an extensive understanding of the CS is vital for furthering the medical care of future cardiac patients.