The cavoatrial junction is the point at which the superior vena cava

Superior vena cava

The superior vena cava is truly superior, a large diameter, yet short, vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium...

 meets and melds into the superior wall of the cardiac

Heart

The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

 right atrium. Both the superior and inferior vena cava

Inferior vena cava

The inferior vena cava , also known as the posterior vena cava, is the large vein that carries de-oxygenated blood from the lower half of the body into the right atrium of the heart....

e enter the right atrium, but only the superior entry is called the cavoatrial junction. This junction marks the inferior end of the superior vena cava

Superior vena cava

The superior vena cava is truly superior, a large diameter, yet short, vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium...

, the continuation below that point being considered part of the heart.

For purposes of radiographic

Radiography

Radiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....

 visualization, the most reliable indicator of junction location is to find the carina

Carina

Carina may refer to:* Carina, a given name in Portugal and some other countries. It is a pet form of Cara, which can mean either "beloved" in Italian or "friend" in the Irish language-Locations:Carina is the name of the towns or villages:...

, then observe the vertebrae it overlies. The junction will lie two vertebral body units below the carina, counting the single intervertebral disc

Intervertebral disc

Intervertebral discs lie between adjacent vertebrae in the spine. Each disc forms a cartilaginous joint to allow slight movement of the vertebrae, and acts as a ligament to hold the vertebrae together.-Structure:...

 between them, but not the disc below them. It has been demonstrated that the more ordinary method of looking for the "bulge" in the cardiac outline is unreliable, since cardiac or other thoracic

Thorax

The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...

 pathology can shift the apparent position of that landmark.

When patients are hospitalized, they may need to receive solutions and medications that, if given through an ordinary intravenous therapy

Intravenous therapy

Intravenous therapy or IV therapy is the infusion of liquid substances directly into a vein. The word intravenous simply means "within a vein". Therapies administered intravenously are often called specialty pharmaceuticals...

 catheter, would severely damage both blood cells and the vascular system. In these cases, it is common to insert a central venous catheter

Central venous catheter

In medicine, a central venous catheter is a catheter placed into a large vein in the neck , chest or groin...

. All such catheters placed for the purpose of venous access and being inserted in the upper body will ideally have the tip placed within the superior vena cava at or just above the Cavoatrial junction. Passing the line through the junction and into the atrium is to be avoided, as the result may be cardiac arrythmia

Cardiac dysrhythmia

Cardiac dysrhythmia is any of a large and heterogeneous group of conditions in which there is abnormal electrical activity in the heart. The heart beat may be too fast or too slow, and may be regular or irregular.Some arrhythmias are life-threatening medical emergencies that can result in cardiac...

s and even cardiac tamponade

Cardiac tamponade

Cardiac tamponade, also known as pericardial tamponade, is an emergency condition in which fluid accumulates in the pericardium ....

, a potentially fatal outcome. For this reason, all placements should be verified by a chest X-ray before the line can be used.