The cavoatrial junction (CAJ) is the point at which the

superior vena cava The superior vena cava (SVC) is the superior of the two venae cavae, the great venous trunks that return deoxygenated blood from the systemic circulation to the right atrium of the heart. It is a large-diameter (24 mm) short length vei ...

meets and melds into the

superior Superior may refer to: *Superior (hierarchy), something which is higher in a hierarchical structure of any kind Places * Superior (proposed U.S. state), an unsuccessful proposal for the Upper Peninsula of Michigan to form a separate state *Lak ...

wall of the

cardiac The heart is a muscular organ found in humans and other animals. This organ pumps blood through the blood vessels. The heart and blood vessels together make the circulatory system. The pumped blood carries oxygen and nutrients to the tissu ...

right atrium. Both the superior and

inferior vena cava The inferior vena cava is a large vein that carries the deoxygenated blood from the lower and middle body into the right atrium of the heart. It is formed by the joining of the right and the left common iliac veins, usually at the level of the ...

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

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

radiographic Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical ("diagnostic" radiography and "therapeu ...

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

carina Carina may refer to: Places Australia * Carina, Queensland, a suburb in Brisbane * Carina Heights, Queensland, a suburb in Brisbane * Carina, Victoria, a locality in Mildura Serbia * Carina, Osečina, a village in the Kolubara District ...

, then observe the

vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

e it overlies. The junction will lie two vertebral body units (VBUs) below the carina, counting the single

intervertebral disc An intervertebral disc (British English), also spelled intervertebral disk (American English), lies between adjacent vertebrae in the vertebral column. Each disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the ver ...

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 The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main ...

pathology can shift the apparent position of that landmark. Hospitalized patients may need to receive solutions and medications that, if given through an ordinary

intravenous therapy Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutr ...

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

central venous catheter A central venous catheter (CVC), also known as a central line (c-line), central venous line, or central venous access catheter, is a catheter placed into a large vein. It is a form of venous access. Placement of larger catheters in more centr ...

. 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 avoided by some practitioners, as they fear the result may be cardiac

arrhythmia Arrhythmias, also known as cardiac arrhythmias, are irregularities in the cardiac cycle, heartbeat, including when it is too fast or too slow. Essentially, this is anything but normal sinus rhythm. A resting heart rate that is too fast – ab ...

s and even

cardiac tamponade Cardiac tamponade, also known as pericardial tamponade (), is a compression of the heart due to pericardial effusion (the build-up of pericardial fluid in the pericardium, sac around the heart). Onset may be rapid or gradual. Symptoms typically i ...

, a potentially fatal outcome. However, other practitioners prefer the proximal RA and state that there is no evidence of harm. Modern catheter tip verification systems often rely on ECG readouts which correlate with tip position. A chest xray may still be obtained to confirm or when an ECG is contraindicated.

References

* * Human anatomy Veins of the torso {{circulatory-stub