Concept.
Arteriovenous fistula: The presence of an abnormal channel between the arteries and veins. This abnormal passage between arteries and veins is called fistula of A-V. This lesion is short-circuited due to the connection between A-V for passing through the terminal capillary network.
Congenital A-V fistula (K-T): It is caused by embryonic dysplasia, resulting in vascular malformations and abnormal channels remaining between the A-V during the evolution of the embryo’s mesoderm development. Many tiny A-V branches are often involved, the fistulae are multiple and the lesions are diffuse. When the fistula is small, there is usually no vascular pulsation or murmur. The fistula is often difficult to visualize on arteriography. Diagnosis and treatment can be difficult.
Pathophysiology.
A-V fistulas originate from the same capillary plexus in the interstitial lobes, and the A-V traffic with each other and replace each other functionally. Normal adult vessels are formed from 3 stages of vascular stretching, anastomosis, atrophy and neovascularization, (undifferentiated capillary phase, reticular phase in which capillaries fuse into a plexiform structure, and vascular basal stem characterization phase).
Multiple fistulas develop and spread, extensively invading adjacent tissues and organs, such as: muscles, bones, nerves and even spreading to the entire limb or trunk.
Subtypes.
1. Stem A-V fistula
The site of the fistula is mostly between the small A-V of the limb, there are traffic branches in the transverse axis direction, one or more fistulas, most of them are large, because there are many blood shunts between the A-V, local intravenous pressure increases, tremor, continuous murmur, varicose veins and sinuous aneurysms can occur.
2. Aneurysmal A-V fistula
The fistula is between the tiny A-V branches, local tissue with aneurysmal enlargement, generally little blood flow, no tremor and murmur.
3.Mixed type
There is a mixture of truncal hemangioma and aneurysmal A-V fistula. The fistula is small and may not change much, while a large fistula may involve cardiac function.
Congenital A-V fistula is not easy to determine where the fistula is located, and those that grow rapidly have serious consequences, and although benign, have the biological characteristics of a malignant tumor.
Prognosis.
1. thickening and growth of the limb
In adolescents, the A-V is present before the closure of the bone scale end, and there is an anastomotic branch of the A-V around it, with rich local blood flow and increased blood nourishment, causing the affected limb to thicken and grow.
The limbs are heavy, swollen, painful, hairy, sweaty, and of unequal length.
2.Hemangioma (birthmark)
Congenital A-V fistula congenital hemangioma coexists in the same area, the hemangioma is purple-orange in color, sometimes flat or higher than the skin, with different sizes, and some lesions surround the whole limb.
3. Increased skin temperature
A-V short circuit, blood-rich limb and venous congestion, local temperature increase by 3~5℃
4. Venous valve insufficiency
Arterial hypertensive blood enters the vein through the fistula, the intravenous pressure increases, the official cavity thickens, the venous valve is damaged, the venous blood flows backwards, the A-V fistula site, the varicose veins, the varicose veins pulsate when the fistula is large, because the venous valve function does not exist making the superficial veins of the limb tortuous, stagnant, dermatitis, hyperpigmentation, eczema, stubborn ulcers, bleeding.
5. murmur and tremor
There may be scattered tremulous murmurs along the vascular course of the affected limb.
6.Inadequate arterial blood supply
A few extremities are cold, pigmented, or even gangrenous.
7, large fistulae with long duration, decreased peripheral blood resistance, increased cardiac output per beat, and heart failure occurs.
Auxiliary examinations.
1, color Doppler ultrasound to understand the blood shunt
2. peripheral venous manometry and oxygen measurement to confirm the presence of A-V short-circuit reflux
3.Arteriography
Diagnosis: (triple sign)
1.Pulsatile masses
2.Tremor
3, murmur
Treatment.
Surgery, before the closure of the bone scale, and before the absence of cardiovascular complications surgical radical treatment is effective.
Surgical indications.
1, rapid growth, with obvious symptoms, nearly early surgery, children before the age of 6 years with good results.
2, slow growth, although no obvious symptoms, no self-healing possible, lesion progression, should also be near early surgery.
3, lesions involving surrounding tissues, such as nerve invasion after pain, after the skin complications of bleeding, ulcers or infection, visceral A-V fistula, digestive system A-V fistula, causing bleeding or intra-pulmonary A-V fistula appear cyanosis, shortness of breath, etc., should be operated nearly early.
4. Complicated heart failure.
Surgical procedures.
1, lesion excision Applicable to limited lesions
2, A-V fistula ligation of major A-V branches For extensive or deep lesions, as well as recurrent infection, ulceration or bleeding
3.Intra-arterial embolization Using gelatin sponge, anhydrous alcohol to dehydrate the tissue, protein coagulation, endothelial cell denaturation, and vascular constriction to form thrombus.
4. Amputation or finger amputation Involving the whole limb or the end of the limb, with severe infection, ulceration, bleeding, necrosis or heart failure.
Care.
1.Guide the patient to pay attention to the protection of the affected limb, apply elastic bandage and elastic stocking for recurrence after non-surgical treatment, avoid strenuous exercise and prevent trauma.
2.After arterial embolization, the puncture site should be pressed with sandbag for 4~6 hours and bed rest for 12 hours. Observe whether there is bleeding or hematoma, if there is bleeding, compression should be applied until the bleeding stops, and then compression bandage should be applied to pay attention to the distal blood supply of the limb.
3. Prevent potential complications, such as bleeding, trauma, and infection.