| Arteriovenous fistula | |
|---|---|
 | |
| Illustration of an arteriovenous fistula | |
| Specialty | Cardiology  |
Anarteriovenous fistula is an abnormal connection or passageway between anartery and avein.[1] It may becongenital, surgically created forhemodialysis treatments, or acquired due topathologic process, such astrauma or erosion of an arterialaneurysm.[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 likeberry aneurysm, acerebral arteriovenous malformation can rupture causingsubarachnoid hemorrhage.[4]
The cause of this condition include
Surgically createdCimino 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 theabdominal aorta, it can lead to a large decrease inperipheral resistance. This lowered peripheral resistance causes the heart to increasecardiac output to maintain proper blood flow to all tissues. The physical manifestations of this typically consist of a relatively normal systolicblood pressure accompanied by decreased diastolic blood pressure, resulting in a widerpulse pressure.[citation needed]
Normal blood flow in thebrachial 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 andshear stress, but the vein dilates more and becomes "arterialized". In one study, thecephalic vein increased from 2.3 mm to 6.3 mm diameter after 2 months. When the vein is large enough to allowcannulation, the fistula is defined as "mature".[7]
An arteriovenous fistula can increasepreload.[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]
Media related toArteriovenous fistula at Wikimedia Commons