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An arteriovenous malformation (AVM) is an abnormal connection between arteries and veins, bypassing the capillary system. Usually congenital , this vascular anomaly is widely known because of its occurrence in the central nervous system (usually as a cerebral AVM ), but can appear anywhere in the body.
A cerebral AVM diagnosis is established by neuroimaging studies after a complete neurological and physical examination. [5] [13] Three main techniques are used to visualize the brain and search for an AVM: computed tomography (CT), magnetic resonance imaging (MRI), and cerebral angiography. [13]
With AVM, this whole capillary bed isn’t there, and a group of arteries directly link up with a group of veins instead. The vessels in the AVM can start to tangle up and are called a nidus, which is Latin for “nest”. When a single artery and a single vein link up abnormally like this, it’s called an arteriovenous fistula.
A vascular malformation is a type of vascular anomaly. [2] They may cause aesthetic problems as they have a growth cycle, and can continue to grow throughout life. Vascular malformations of the brain include those involving capillaries, and those involving the veins and arteries.
Pronunciation follows convention outside the medical field, in which acronyms are generally pronounced as if they were a word (JAMA, SIDS), initialisms are generally pronounced as individual letters (DNA, SSRI), and abbreviations generally use the expansion (soln. = "solution", sup. = "superior").
In one study, the cephalic vein increased from 2.3 mm to 6.3 mm diameter after 2 months. When the vein is large enough to allow cannulation, the fistula is defined as "mature". [7] An arteriovenous fistula can increase preload. [8] AV shunts also decrease the afterload of the heart.
Vein of Galen malformations are devastating complications. Studies have shown that 77% of untreated cases result in mortality. [13] Even after surgical treatment, the mortality rate remains as high as 39.4%. [13] Most cases occur during infancy when the mortality rates are at their highest.
The main discussion of these abbreviations in the context of drug prescriptions and other medical prescriptions is at List of abbreviations used in medical prescriptions. Some of these abbreviations are best not used, as marked and explained here.