A dissection is a tear within the wall of a blood vessel, which allows blood to separate the wall layers. Usually, a dissection is an arterial wall dissection, but vein wall dissections (VWD) have been documented.
By separating a portion of the wall of the artery (a layer of the
tunica media
The tunica media (New Latin "middle coat"), or media for short, is the middle tunica (layer) of an artery
An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts o ...
or in some cases
tunica intima
The tunica intima (New Latin "inner coat"), or intima for short, is the innermost tunica (layer) of an artery or vein. It is made up of one layer of endothelial cells and is supported by an internal elastic lamina. The endothelial cells are in ...
), a dissection creates two
lumens
The lumen (symbol: lm) is the unit of luminous flux, a measure of the total quantity of visible light emitted by a source per unit of time, in the International System of Units (SI). Luminous flux differs from power ( radiant flux) in that radia ...
or passages within the vessel, the native or true lumen, and the "false lumen" created by the new space within the wall of the artery. It is not yet clear if the tear in the innermost layer, the
tunica intima
The tunica intima (New Latin "inner coat"), or intima for short, is the innermost tunica (layer) of an artery or vein. It is made up of one layer of endothelial cells and is supported by an internal elastic lamina. The endothelial cells are in ...
, is secondary to the tear in the
tunica media
The tunica media (New Latin "middle coat"), or media for short, is the middle tunica (layer) of an artery
An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts o ...
. Dissections originating in the
tunica media
The tunica media (New Latin "middle coat"), or media for short, is the middle tunica (layer) of an artery
An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts o ...
are caused by disruption of the
vasa vasorum
Vasa vasorum are small blood vessels that comprise a vascular network supplying the walls of large blood vessels, such as elastic arteries (e.g., the aorta) and large veins (e.g., the venae cavae).
The name derives . Occasionally two differe ...
. It is thought that dysfunction in the
vasa vasorum
Vasa vasorum are small blood vessels that comprise a vascular network supplying the walls of large blood vessels, such as elastic arteries (e.g., the aorta) and large veins (e.g., the venae cavae).
The name derives . Occasionally two differe ...
is an underlying cause of dissections.
Description
Dissections become threatening to the health of the organism when growth of the false lumen prevents
perfusion
Perfusion is the passage of fluid through the circulatory system or lymphatic system to an organ or a tissue, usually referring to the delivery of blood to a capillary bed in tissue. Perfusion is measured as the rate at which blood is deliv ...
of the true lumen and the end organs perfused by the true lumen. For example, in an
aortic dissection
Aortic dissection (AD) occurs when an injury to the innermost layer of the aorta allows blood to flow between the layers of the aortic wall, forcing the layers apart. In most cases, this is associated with a sudden onset of severe chest or ...
, if the
left subclavian artery
In human anatomy, the subclavian arteries are paired major arteries of the upper thorax, below the clavicle. They receive blood from the aortic arch. The left subclavian artery supplies blood to the left arm and the right subclavian artery supplie ...
orifice
An orifice is any opening, mouth, hole or vent, as in a pipe, a plate, or a body
* Body orifice, any opening in the body of a human or animal
*Orifice plate, a restriction used to measure flow or to control pressure or flow, sometimes given specia ...
were
distal
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
to the origin of the dissection, then the left subclavian would be said to be perfused by the false lumen, while the
proximal
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position ...
to the dissection, would be perfused by the true lumen proximal to the dissection.
Vessels and organs that are perfused from a false lumen may be well-perfused to varying degrees, from normal perfusion to no perfusion. In some cases, little to no end-organ damage or failure may be seen. Similarly, vessels and organs perfused from the true lumen but distal to the dissection may be perfused to varying degrees. In the above example, if the aortic dissection extended from proximal to the left subclavian artery takeoff to the mid descending
aorta
The aorta ( ) is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller arteries (the common iliac arteries). The aorta distributes ...
, the
common iliac arteries
The common iliac artery is a large artery of the abdomen paired on each side. It originates from the aortic bifurcation at the level of the 4th lumbar vertebra. It ends in front of the sacroiliac joint, one on either side, and each bifurcates i ...
would be perfused from the true lumen distal to the dissection but would be at risk for malperfusion due to occlusion of the true lumen of the aorta by the false lumen.
Types
Examples include:
*
Aortic dissection
Aortic dissection (AD) occurs when an injury to the innermost layer of the aorta allows blood to flow between the layers of the aortic wall, forcing the layers apart. In most cases, this is associated with a sudden onset of severe chest or ...
(
aorta
The aorta ( ) is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller arteries (the common iliac arteries). The aorta distributes ...
)
*
Coronary artery dissection
Spontaneous coronary artery dissection (SCAD) is an uncommon but potentially lethal condition in which one of the arteries that supply the heart spontaneously develops a blood collection, or hematoma, within the artery wall. This leads to a separ ...
(
coronary artery
The coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart muscle. The heart requires a continuous supply of oxygen to function and survive, much like any other tissue or organ o ...
) also referred to as
spontaneous coronary artery dissection
Spontaneous coronary artery dissection (SCAD) is an uncommon but potentially lethal condition in which one of the arteries that supply the heart spontaneously develops a blood collection, or hematoma, within the artery wall. This leads to a separ ...
or SCAD
*
Pulmonary artery dissection
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...
(
pulmonary artery
A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs. The largest pulmonary artery is the ''main pulmonary artery'' or ''pulmonary trunk'' from the heart, and ...
) also referred to as PA Dissections
*
Carotid artery dissection
Carotid artery dissection is a separation of the layers of the artery wall supplying oxygen-bearing blood to the head and brain and is the most common cause of stroke in young adults. (Dissection is a blister-like de-lamination between the oute ...
(
carotid artery Carotid artery may refer to:
* Common carotid artery, often "carotids" or "carotid", an artery on each side of the neck which divides into the external carotid artery and internal carotid artery
* External carotid artery
The external carotid arte ...
)
*
Vertebral artery dissection
Vertebral artery dissection (VAD) is a flap-like tear of the inner lining of the vertebral artery, which is located in the neck and supplies blood to the brain. After the tear, blood enters the arterial wall and forms a blood clot, thickening ...
(
vertebral artery
The vertebral arteries are major arteries of the neck. Typically, the vertebral arteries originate from the subclavian arteries. Each vessel courses superiorly along each side of the neck, merging within the skull to form the single, midline ...
)
Carotid and vertebral artery dissection are grouped together as "
cervical artery dissection
Cervical artery dissection is dissection of one of the layers that compose the carotid and vertebral artery in the neck (cervix). They include:
* Carotid artery dissection, a separation of the layers of the artery wall supplying oxygen-bearing blo ...
" (CeAD).
Common Features
As a disease family, arterial dissections share common features, including shared genetic risk variants, and commonly perturbed molecular pathways. This includes dysfunction of the
TGF-β
Transforming growth factor beta (TGF-β) is a multifunctional cytokine belonging to the transforming growth factor superfamily that includes three different mammalian isoforms (TGF-β 1 to 3, HGNC symbols TGFB1, TGFB2, TGFB3) and many other ...
pathway,
extracellular matrix
In biology, the extracellular matrix (ECM), also called intercellular matrix, is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide struc ...
pathways, cellular metabolism and
vascular smooth muscle cell
Vascular smooth muscle is the type of smooth muscle that makes up most of the walls of blood vessels.
Structure
Vascular smooth muscle refers to the particular type of smooth muscle found within, and composing the majority of the wall of blood ve ...
contractility. Variants in genes including Collagen genes ''COL1A1, COL1A2, COL3A1, COL4A1, COL5A2'', as well as
extracellular matrix
In biology, the extracellular matrix (ECM), also called intercellular matrix, is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide struc ...
genes ''FBN1, FBN2, LOX, MFAP5'';
TGF-β
Transforming growth factor beta (TGF-β) is a multifunctional cytokine belonging to the transforming growth factor superfamily that includes three different mammalian isoforms (TGF-β 1 to 3, HGNC symbols TGFB1, TGFB2, TGFB3) and many other ...
pathways genes ''
LRP1
Low density lipoprotein receptor-related protein 1 (LRP1), also known as alpha-2-macroglobulin receptor (A2MR), apolipoprotein E receptor (APOER) or cluster of differentiation 91 (CD91), is a protein forming a receptor found in the plasma membra ...
, TGFBR2, TGFB2''; cytoskeletal/contractile pathway genes and ''
PHACTR1
Phosphatase and actin regulator 1 (PHACTR1) is a protein that in humans is encoded by the ''PHACTR1'' gene on chromosome 6. It is most significantly expressed in the globus pallidus of the brain. PHACTR1 is an actin and protein phosphatase 1 ( ...
, MYLK, PRKG1, and TLN1''; and
vascular smooth muscle cell
Vascular smooth muscle is the type of smooth muscle that makes up most of the walls of blood vessels.
Structure
Vascular smooth muscle refers to the particular type of smooth muscle found within, and composing the majority of the wall of blood ve ...
gene ''SLC2A10'' have all been implicated in at least two types of arterial dissection.