Vascular malformations are abnormal clusters of blood vessels that occur during fetal development. 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 create problems with the normal flow of blood by preventing 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 some capillaries, it creates a lack of oxygen and a build up of wastes in the body tissue that would normally get blood from those capillaries. These potentially dangerous malformation are called arteriovenous malformations, or AVMs.
While they sometimes grow quite rapidly, their growth is usually gradual and steady. Without treatment, a vascular malformation will not diminish or disappear.
There are a number of different sub-types of vascular malformations, depending on the predominant channel abnormality. These include:
- Capillary malformations (portwine stains)
- Lymphatic malformations
- Venous malformations
- Arteriovenous malformations
- Combined vascular malformations
The severity of these malformations varies greatly both within and among these clinical groups. In addition to being classified by predominant channel abnormality, 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 thus require specific treatments to manage the problem. 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.
Symptoms of Vascular Malformations
When located in an extremity, CVMs may show us as a birthmark, a visible or palpable mass of blood vessels, or may stimulate the development of collateral blood vessels in the form of varicose veins, or 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 sized from small to huge and at their surface the vessels may be vulnerable to injury and bleed or may even break down and ulcerate. AVFs, by "stealing" blood from the circulation beyond them may cause "ischemic" pain, which is the medical term for pain that results when circulation is so restricted that the tissues, and the nerves serving them, do not get enough blood.
How are vascular malformations diagnosed?
These lesions are diagnosed by both physical examination and by using a number of imaging techniques, including magnetic resonance imaging (MRI) and ultrasonography. In some cases, an angiogram is needed to assist in detailed treatment planning. These tests are briefly described below:
Magnetic resonance imaging (MRI)-This technique uses a magnetic field and radio waves to produce three-dimensional images of the inside of the body. Since the child must lie still for up to 1 hour, sedation is frequently given through an intravenous catheter (a small needle placed in the arm or foot). Some younger children may require general anesthesia.
Ultrasonography - This technique uses sound waves to take pictures of the inside of the body. Sedation is not required for this test.
Angiogram - This is a study of the blood vessels that uses a special X-ray machine. A dye is injected into the bloodstream through a tube which is placed in an artery in the leg. This allows the doctor to see the blood vessels and take X-rays. An angiogram is done either with sedation or under general anesthesia.
How are vascular malformations managed?
Management of vascular malformations is dependent upon the type and location of the malformation as well as its depth.
In making treatment decisions, physicians evaluate the highly individual nature of AVMs and make recommendations case-by-case based on the exact location of any malformation and the specific symptoms and risks posed by the malformation. As a general rule, vascular malformations should be treated for specific indications: persistent pain, ulceration, bleeding, causing blood clots, obstructing major vessels, causing progressive limb asymmetry by overgrowth, and for cosmetic indications or because the vascular mass is cumbersome and leads to a badly misshapen limb or interferes with extremity function in a mechanical way.
People diagnosed with a vascular malformation may only require a physician monitoring them closely for any signs of a hemorrhage; this type of management is often called watchful waiting. Stable AVMs may never require treatment.
Observation and the use of supportive treatments (e.g., compression garments and drug therapy) are sometimes recommended. 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. While surgery is complex and was previously associated with the risk of blood loss, advances in technology now enable removal to be more safely performed. The management of combined vascular lesions is far more complex.
In general, vascular malformations are treated with:
- Surgery- the surgeon ties off and removes the arteries that feed blood into the malformation and then removes the malformation
- Embolization- Catheters are placed (usually through a groin vessel) and 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
These catheter embolization techniques can be used to control lesions without surgery. They can also shrink larger vascular malformations to make them more readily treatable by surgery and
- Radiosurgery- the physician aims highly focused radiation directly through the skull and brain and into the malformation itself to damage the blood vessels that comprise the malformation and eventually cause them to close
Frequently, AVMs are being treated with a combination of these three therapies.