The cavoatrial junction (CAJ) is the point at which the superior vena cava 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 *Lake ...

wall of the cardiac right atrium. Both the superior and inferior vena cavae 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, the continuation below that point being considered part of the heart. For purposes of radiographic visualization, the most reliable indicator of junction location is to find the carina, then observe the

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

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

intervertebral disc An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column. Each disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold t ...

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 or chest is a part of the anatomy of humans, 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 divisions of the crea ...

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 nutri ...

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 central ...

. 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

arrythmia Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults ...

s and even cardiac tamponade, 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