The abnormal formation or development of blood vessels is generally referred to as vascular malformation. Abnormal blood vessel structure is usually congenital, meaning it is present at birth.
Abnormal blood vessels can prevent enough oxygenated blood from filling capillaries, the tiny blood vessels that connect the body's arteries and veins. In some people with vascular malformations, blood travels directly from the arteries into the veins without ever having reached the capillary system. When blood does not fill the capillaries, the blood tissues that would normally receive blood from them experience a lack of oxygen, as well as a buildup of waste products.
The severity of these malformations varies greatly both within and among the following clinical groups:
- Arteriovenous malformations
- Capillary malformations (portwine stains)
- Combined vascular malformations
- Lymphatic malformations
- Venous malformations
Vascular malformations are categorized as either slow flow or fast flow. These terms refer to the rapidity of blood flowing through the lesion.
- Fast-flow lesions can lead to high output heart failure and may require specific treatment. Arteriovenous malformations are fast-flow lesions.
- Capillary, lymphatic, and venous malformations are considered slow-flow lesions. Combined malformations may be either slow or fast flow.
When located in an extremity, vascular malformations might show as a birthmark, may stimulate the development of collateral blood vessels in the form of varicose veins, or can produce an enlargement of the limb or a lengthening of the limb by stimulating its bony growth centers.
The localized masses may be of various size, from small to huge, and at their surface the vessels may be vulnerable to injury and bleed or may break down and ulcerate.
These lesions are diagnosed by both physical examination and by using a number of imaging techniques, including magnetic resonance imaging (Cardiovascular MRI) and ultrasonography. In some cases, an angiogram is needed to assist in detailed treatment planning.
Vascular malformations posses a highly individual nature and, therefore, treatment is decided case-by-case, based on the exact location of any malformation and the specific symptoms and risks posed by the malformation. Some vascular malformations may only require monitoring or compression garments and drug therapy.
For lesions that are only superficial, laser therapy is commonly used. Lesions that are deep may, however, require surgical removal and other therapies such as sclerotherapy.
Vascular malformations that cause persistent pain, ulceration, bleeding, blood clots, obstruction of major vessels, progressive limb asymmetry by overgrowth, or that interfere with limb function should be treated, often with the following:
The surgeon ties off and removes the arteries that feed blood into the malformation and removes the malformation.
Catheters are advanced into the lesions, and the malformed vessels are blocked, or embolized, with a variety of injectable particles, substances, or devices such as polyvinyl foam, biological glues, and absolute alcohol.
Highly focused radiation is aimed directly at the blood vessels that comprise the malformation and cause them to close.