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Endovascular treatment of arteriovenous malformation (AVM)
Arteriovenous malformation (AVM) is a serious medical condition. Some individuals may not have symptoms of AVM until a bleeding event occurs. AVMs are most commonly found in the brain and spinal cord, but they can be present anywhere in the body. The decision to treat the malformation depends on various factors, including the consideration of the risk that an AVM may bleed and cause significant or even life-threatening damage if left untreated, especially when located in the brain. Available treatments are highly effective. The team at Pulse Cardiology Center will discuss with you the details of your malformation, its size and location, and other factors to consider and apply the treatment options that are best for you.
What is an arteriovenous malformation (AVM) and how does it develop?
An arteriovenous malformation (AVM) is an irregular tangle (like a bird’s nest) of blood vessels. The tangle consists of arteries that would normally supply brain tissue and veins that would normally drain brain tissue. It is a pathological network of blood vessels in the brain (AVM) or in the dura mater (dAVF). Normally, capillaries – small blood vessels that nourish the surrounding tissue – are present between the arteries and veins. In AVM, capillaries are absent, and blood flows directly from the artery into the vein. This part of the blood does not participate in nourishing the brain and surrounding tissues. The blood vessels of an AVM are more fragile than normal and can rupture, causing bleeding in the brain.
Arteriovenous malformations (AVMs) of the brain develop during the prenatal period (before birth) and often manifest symptoms in the second or third decade of life, commonly after a bleeding event.
How is an arteriovenous malformation of the brain (AVM) detected?
All symptoms are a result of compression (pressure on parts of the brain), ischemia, bleeding, or a combination of these factors.
1.If there hasn’t been any bleeding:
- Chronic headaches
- Epileptic seizures
- Various neurological symptoms depending on the location of the AVM, as a result of brain compression or ischemia (speech impairment, dizziness, confusion, memory loss, paralysis, etc.)
2.If there has been bleeding:
- Headache
- Loss of consciousness
- Nausea
- Vomiting
- Paralysis and paresis (muscle and sensory function impairment) in different areas
Diagnostic methods: CT and CTA; MRI and MRA; definitive confirmation is obtained through DSA (Digital Subtraction Angiography).
Why is endovascular treatment used?
AVMs and dAVFs can be treated with surgical operation, endovascular treatment, radiosurgery (gamma knife), or a combination of these methods. The drawback of gamma knife treatment is the 2-year period required for full effect, during which the patient is at risk of bleeding. The goal of treatment is to completely eliminate the AVM from circulation. Endovascular treatment involves excluding the AVM or dAVF from circulation by injecting liquid embolic material (NBCA, Onyx) into the blood vessels that make up the malformation. The liquid material hardens in the blood vessels of the malformation, permanently closing them off (blocking them). This technique is used worldwide with great success.
When is endovascular treatment used?
The therapeutic strategy for AVM or dAVF is determined by an experienced multidisciplinary team consisting of neurosurgeons, neuroradiologists, and interventional radiologist.
Bleeding in the brain tissue, ventricles, or the space around the brain due to the presence of AVM or dAVF is an urgent condition. Such a condition can lead to brain damage and death. These malformations do not have a tendency to re-rupture quickly, which is why treatment is performed after the consequences of bleeding in the brain have subsided. However, once they have bled, the chance of another rupture within the first year is 9 times higher. For this reason, all bleeding AVMs and dAVFs should be treated. If AVM or dAVF is associated with an aneurysm (which is often the site of bleeding), more urgent treatment is necessary.
Due to a wide range of nonspecific symptoms, unruptured AVMs and dAVFs are often unrecognized. They are usually discovered incidentally, primarily on a brain CT scan. In the case of unruptured malformations, it is necessary to carefully weigh the risk of intervention against the natural course of the disease. If the risk of intervention is higher, in consultation with the patient and their family, a decision is made whether to proceed with treatment or adopt a conservative approach – not to treat but to monitor the condition. Patients with AVM or dAVF should avoid strenuous physical exertion. Smaller and deep-seated AVMs are more dangerous as they are more prone to bleeding. Increased blood pressure and higher blood volume during pregnancy increase the risk of bleeding.
How does the endovascular treatment of brain arteriovenous malformation (AVM) is perfomed?
- The patient is placed under general anesthesia, and after a small incision in the groin area, a catheter is inserted into the femoral artery. Every movement is controlled and monitored on a screen above the operating table.
- The catheter is advanced from the femoral artery to the large blood vessels of the neck (carotid or vertebral arteries).
- A microcatheter is then navigated through the guiding catheter, through the arteries of the brain, until its tip reaches the AVM.
- Liquid embolic material is gradually injected through the microcatheter, filling the blood vessels of the AVM and thereby excluding it from circulation.
- After the completion of the procedure, the patient is often kept under general anesthesia for up to 24 hours to prevent bleeding due to a sudden increase in blood pressure upon awakening from anesthesia. This time is necessary for the cerebrovascular system to stabilize.
- After this period, the patient wakes up from anesthesia with a bandaged groin. Strict bed rest with the extended leg and bandage is required for 24 hours after the procedure unless a specialized closure device was used, in which case a few hours of bed rest are sufficient.
Risks of endovascular treatment of AVM?
Every surgery carries certain risks, including endovascular treatment of AVM. The possibility of AVM rupture and bleeding, thrombosis of healthy blood vessels, and migration of embolic material into healthy blood vessels. This can lead to permanent disability or death.
What to expect after embolization?
Recovery
Most patients with unruptured AVMs can resume normal daily activities, including work, exercise, and travel, as before the treatment.
The recovery of patients after endovascular treatment of a ruptured aneurysm will depend on the severity of the clinical condition. Brain bleeding can lead to stroke and/or patient death (even though the aneurysm has been secured with treatment). Some of these symptoms may improve over time. Support from family and loved ones is important during the recovery period.
Monitoring
The goal of treatment is complete elimination of the AVM. When it is not possible to eliminate the malformation in one session, endovascular treatment is performed in two or more sessions. In certain cases, complete elimination cannot be achieved through embolization alone. Combining embolization, surgery, and radiotherapy (gamma knife) can yield good results in complex cases. Microsurgical operations have limitations when the malformation is inaccessible, while radiotherapy is not suitable for larger AVMs.
Regular follow-up examinations are conducted to monitor the condition of the malformation. Follow-up visits may involve angiography or magnetic resonance imaging. Based on the findings, the need for additional treatment is assessed.
When to contact a doctor after the procedure?
- If there are signs of infection at the incision site (groin): redness, swelling, pain, drainage.
- In case of sudden pain at the arterial puncture site (groin), loss of sensation in the leg, leg swelling.
- Call emergency services for severe headache, nausea and vomiting, or stiff neck (signs of AVM rupture).
FREQUENTLY ASKED QUESTIONS ABOUT ARTERIOVENOUS MALFORMATION – AVM
Are there any prevention methods for arteriovenous malformations (AVM)?
Arteriovenous malformations (AVMs) cannot be prevented as they are believed to be congenital, meaning present at birth. However, if you notice any of the symptoms mentioned in this text, it is important to seek medical attention immediately. Prompt response to the development of symptoms is the best approach.
What is the difference between arteriovenous malformation, aneurysm, hemangioma, cavernous malformation, and fistula?
An aneurysm is a weakened, bulging area in an artery, commonly occurring at the site where two arteries branch. An aneurysm can develop as a complication of arteriovenous malformation (AVM).
Hemangiomas are vascular malformations that are visible on the skin. They are also known as “strawberry marks.” They are not dangerous and do not require treatment.
Cavernous malformations are a type of vascular lesion. Unlike AVMs, they are filled with slow blood flow that often clots. They may bleed, but the bleeding is usually not as severe as in AVMs and often does not cause symptoms.
Fistula is a general term for an abnormal connection between blood vessels. Arteriovenous fistulas are found in the tissue covering the brain and spinal cord (dura mater or arachnoid). AVMs are located within the brain tissue.
Do all arteriovenous malformations (AVMs) cause bleeding?
Not all arteriovenous malformations (AVMs) cause bleeding. Some AVMs never bleed and may not even cause symptoms or health problems throughout a person’s life. Some are only discovered incidentally during imaging for other reasons or after death during autopsy.
AVMs can cause other health problems besides bleeding. Some AVMs that grow and become large can compress certain tissues and cause tissue damage, damage to nerve cells, and other cellular damage in that area. If an AVM is large enough and located in a vital area, the lack of capillaries between the arteries and veins can lead to a lack of oxygen, nutrients, and waste exchange in the tissue of that area. This can result in tissue necrosis.
Can cerebral arteriovenous malformations (AVMs) be fatal?
Yes, unfortunately, they can be. The severity or fatality of cerebral arteriovenous malformations (AVMs) depends on their size and location. Massive bleeding from a ruptured AVM in the brain can be life-threatening. However, some individuals have an AVM and never experience symptoms or health issues.
Does the location of a headache indicate the location of an arteriovenous malformation (AVM)?
Not necessarily. It can, but most often, the location of a headache is not specific to the area of the AVM.
Does a pregnant woman with arteriovenous malformations (AVMs) have an increased risk?
Due to the increase in blood volume and blood pressure that accompanies pregnancy, being pregnant with an AVM can increase the risk of bleeding from the AVM. In some individuals, pregnancy-related changes can lead to the sudden onset or worsening of AVM symptoms.