| Arteriovenous fistula | |
|---|---|
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| Illustration of an arteriovenous fistula | |
| Specialty | Cardiology  |
An arteriovenous fistula is an abnormal connection or passageway between an artery and a vein. [1] It may be congenital, surgically created for hemodialysis treatments, or acquired due to pathologic process, such as trauma or erosion of an arterial aneurysm. [2]
Hereditary hemorrhagic telangiectasia is a condition where there is direct connection between arterioles and venules without intervening capillary beds, at the mucocutaneous region and internal bodily organs. Those who are affected by this conditions usually do not experience any symptoms. Difficulty in breathing is the most common symptom for those who experience symptoms. [3]
Just like berry aneurysm, a cerebral arteriovenous malformation can rupture causing subarachnoid hemorrhage. [4]
The cause of this condition include
Surgically created Cimino fistula is used as a vascular access for hemodialysis. Blood must be aspirated from the body of the patient, and since arteries are not easy to reach compared to the veins, blood may be aspirated from veins. The problem is that the walls of the veins are thin compared to those of the arteries. The AV fistula is the solution for this problem because, after 4–6 weeks, the walls of the veins become thicker due to the high arterial pressure. Thus, this vein can now tolerate needles during hemodialysis sessions.
When an arteriovenous fistula is formed involving a major artery like the abdominal aorta, it can lead to a large decrease in peripheral resistance. This lowered peripheral resistance causes the heart to increase cardiac output to maintain proper blood flow to all tissues. The physical manifestations of this typically consist of a relatively normal systolic blood pressure accompanied by decreased diastolic blood pressure, resulting in a wider pulse pressure.[ citation needed ]
Normal blood flow in the brachial artery is 85 to 110 milliliters per minute (mL/min). After the creation of a fistula, the blood flow increases to 400–500 mL/min immediately, and 700–1,000 mL/min within 1 month. A brachiocephalic fistula above the elbow has a greater flow rate than a radiocephalic fistula at the wrist. Both the artery and the vein dilate and elongate in response to the greater blood flow and shear stress, but the vein dilates more and becomes "arterialized". 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. This is because the blood bypasses the arterioles which results in a decrease in the total peripheral resistance (TPR). AV shunts increase both the rate and volume of blood returning to the heart.[ citation needed ]
The diagnosis of this condition can be done via ultrasound[ citation needed ]
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, but can appear anywhere in the body. The symptoms of AVMs can range from none at all to intense pain or bleeding, and they can lead to other serious medical problems.
A cerebral arteriovenous malformation is an abnormal connection between the arteries and veins in the brain—specifically, an arteriovenous malformation in the cerebrum.
Hypertensive retinopathy is damage to the retina and retinal circulation due to high blood pressure.
Cerebrovascular disease includes a variety of medical conditions that affect the blood vessels of the brain and the cerebral circulation. Arteries supplying oxygen and nutrients to the brain are often damaged or deformed in these disorders. The most common presentation of cerebrovascular disease is an ischemic stroke or mini-stroke and sometimes a hemorrhagic stroke. Hypertension is the most important contributing risk factor for stroke and cerebrovascular diseases as it can change the structure of blood vessels and result in atherosclerosis. Atherosclerosis narrows blood vessels in the brain, resulting in decreased cerebral perfusion. Other risk factors that contribute to stroke include smoking and diabetes. Narrowed cerebral arteries can lead to ischemic stroke, but continually elevated blood pressure can also cause tearing of vessels, leading to a hemorrhagic stroke.
Interventional radiology (IR) is a medical specialty that performs various minimally-invasive procedures using medical imaging guidance, such as x-ray fluoroscopy, computed tomography, magnetic resonance imaging, or ultrasound. IR performs both diagnostic and therapeutic procedures through very small incisions or body orifices. Diagnostic IR procedures are those intended to help make a diagnosis or guide further medical treatment, and include image-guided biopsy of a tumor or injection of an imaging contrast agent into a hollow structure, such as a blood vessel or a duct. By contrast, therapeutic IR procedures provide direct treatment—they include catheter-based medicine delivery, medical device placement, and angioplasty of narrowed structures.
Hereditary hemorrhagic telangiectasia (HHT), also known as Osler–Weber–Rendu disease and Osler–Weber–Rendu syndrome, is a rare autosomal dominant genetic disorder that leads to abnormal blood vessel formation in the skin, mucous membranes, and often in organs such as the lungs, liver, and brain.
Intracranial hemorrhage (ICH), also known as intracranial bleed, is bleeding within the skull. Subtypes are intracerebral bleeds, subarachnoid bleeds, epidural bleeds, and subdural bleeds. More often than not it ends in death.
A pseudoaneurysm, also known as a false aneurysm, is a locally contained hematoma outside an artery or the heart due to damage to the vessel wall. The injury passes through all three layers of the arterial wall, causing a leak, which is contained by a new, weak "wall" formed by the products of the clotting cascade. A pseudoaneurysm does not contain any layer of the vessel wall.
Bruit, also called vascular murmur, is the abnormal sound generated by turbulent flow of blood in an artery due to either an area of partial obstruction or a localized high rate of blood flow through an unobstructed artery.
Intraparenchymal hemorrhage (IPH) is one form of intracerebral bleeding in which there is bleeding within brain parenchyma. The other form is intraventricular hemorrhage (IVH).
A vascular bypass is a surgical procedure performed to redirect blood flow from one area to another by reconnecting blood vessels. Often, this is done to bypass around a diseased artery, from an area of normal blood flow to another relatively normal area. It is commonly performed due to inadequate blood flow (ischemia) caused by atherosclerosis, as a part of organ transplantation, or for vascular access in hemodialysis. In general, someone's own vein (autograft) is the preferred graft material for a vascular bypass, but other types of grafts such as polytetrafluoroethylene (Teflon), polyethylene terephthalate (Dacron), or a different person's vein (allograft) are also commonly used. Arteries can also serve as vascular grafts. A surgeon sews the graft to the source and target vessels by hand using surgical suture, creating a surgical anastomosis.
A dural arteriovenous fistula (DAVF) or malformation is an abnormal direct connection (fistula) between a meningeal artery and a meningeal vein or dural venous sinus.
Vascular disease is a class of diseases of the vessels of the circulatory system in the body, including blood vessels – the arteries and veins, and the lymphatic vessels. Vascular disease is a subgroup of cardiovascular disease. Disorders in this vast network of blood and lymph vessels can cause a range of health problems that can sometimes become severe, and fatal. Coronary heart disease for example, is the leading cause of death for men and women in the United States.
In nephrology, vascular access steal syndrome is a syndrome caused by ischemia resulting from a vascular access device that was installed to provide access for the inflow and outflow of blood during hemodialysis.
Vascular access refers to a rapid, direct method of introducing or removing devices or chemicals from the bloodstream. In hemodialysis, vascular access is used to remove the patient's blood so that it can be filtered through the dialyzer. Three primary methods are used to gain access to the blood: an intravenous catheter, an arteriovenous fistula (AV) or a synthetic graft. In the latter two, needles are used to puncture the graft or fistula each time dialysis is performed.
A vascular malformation is a blood vessel or lymph vessel abnormality. Vascular malformations are one of the classifications of vascular anomalies, the other grouping is vascular tumors. They may cause aesthetic problems as they have a growth cycle, and can continue to grow throughout life.
Vascular myelopathy refers to an abnormality of the spinal cord in regard to its blood supply. The blood supply is complicated and supplied by two major vessel groups: the posterior spinal arteries and the anterior spinal arteries—of which the Artery of Adamkiewicz is the largest. Both the posterior and anterior spinal arteries run the entire length of the spinal cord and receive anastomotic (conjoined) vessels in many places. The anterior spinal artery has a less efficient supply of blood and is therefore more susceptible to vascular disease. Whilst atherosclerosis of spinal arteries is rare, necrosis in the anterior artery can be caused by disease in vessels originating from the segmental arteries such as atheroma or aortic dissection.
The Nicoladoni–Branham sign is named after Carl Nicoladoni, who first noticed the phenomenon of the pulse slowing in a patient with right arm phlebarteriectasia when the brachialis artery proximal to it was compressed. In modern medicine, the sign is elicited when pressure is applied to an artery proximal to an arteriovenous fistula and said to be positive if the following occurs:
Parkes Weber syndrome (PWS) is a congenital disorder of the vascular system. It is an extremely rare condition, and its exact prevalence is unknown. It is named after British dermatologist Frederick Parkes Weber, who first described the syndrome in 1907.
Vein of Galen aneurysmal malformations(VGAMs) and Vein of Galen aneurysmal dilations (VGADs) are the most frequent arteriovenous malformations in infants and fetuses. A VGAM consists of a tangled mass of dilated vessels supplied by an enlarged artery. The malformation increases greatly in size with age, although the mechanism of the increase is unknown. Dilation of the great cerebral vein of Galen is a secondary result of the force of arterial blood either directly from an artery via an arteriovenous fistula or by way of a tributary vein that receives the blood directly from an artery. There is usually a venous anomaly downstream from the draining vein that, together with the high blood flow into the great cerebral vein of Galen causes its dilation. The right sided cardiac chambers and pulmonary arteries also develop mild to severe dilation.
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