Stroke

What is a stroke?

A stroke is a sudden blockage in a blood vessel supplying the brain caused by a blood clot. As a result, not enough oxygen can reach this part of the brain resulting in an impairment of neurological function. This can cause a variety of symptoms but usually involves weakness in the limbs on one side of the body, drooping of half of the face, and difficulty in speech or vision. Strokes can be very mild or very severe.


What is a Mechanical Thrombectomy?

If you can remove the blockage soon enough then the symptoms may be, at least partially, reversible. Mechanical thrombectomy is a procedure to remove the blood clot using a special retrieval device and therefore restore normal blood flow. If the clot is removed before it causes permanent damage then the prognosis is usually improved. Thrombectomy has been proven to be an extremely effective treatment and is performed all over the world in specialist hospitals. It can be used in addition to or in-place of clot-busting drugs (thrombolysis) which are given as an intravenous infusion.

Mechanical thrombectomy is performed by specialist doctors called interventional neuroradiologists (INRs).

Mechanical thrombectomy is suitable for many, but not all, stroke patients. If the clot has been present for too long, for example, the risks of the procedure may outweigh the benefits. This will be determined based on CT and MRI scans of the patient. Thrombectomy is performed as soon as possible and up to 24 hours after the time of stroke onset depending on various factors which are carefully considered by the clinical team. However, as with all stroke treatments time is an important factor to patient outcomes and treatments are shown to be most effective when performed shortly after onset.


What are the risks?

Whilst mechanical thrombectomy is generally considered safe, all medical procedures involve risk and we will talk to you and your relatives (if necessary) before the procedure.


Minor, common side effects and risks

  • Occasionally, it may not be possible to retrieve the clot during thrombectomy.

  • During a thrombectomy a contrast dye agent (iodine based) will be injected into the arteries. This allows for the doctor to see the blood vessels and blockage when an X-Ray is taken. Contrast agents are considered safe but have the potential to cause an allergic reaction. The department and team are well equipped to deal with this in the rare event of this happening.

  • The contrast agent used during a thrombectomy is excreted through the kidneys and this may rarely affect your relative’s kidney function. This is more common in patients with pre-existing kidney dysfunction.

  • Usually, the procedure needs to take place under a general anaesthetic, and the anaesthetist will discuss the risks of general anaesthesia prior to the procedure.


Serious but rare risks

Serious complications are rare but may include:

  • Haematoma (bruising or vessel damage around the groin puncture site) may occur. Often there is bruising and sometimes bleeding in the groin. Very occasionally there is damage to the blood vessel requiring a further surgical operation.

  • There is small risk (less than 1%) of causing severe brain injury or death due to the procedure.

  • After the procedure there is sometimes bleeding into the region of the brain where the stroke has occurred. This can cause neurological deterioration and may only be apparent in the days following the stroke.

  • The use of X-rays during any procedure results in a small increase in the risk of developing cancer in the future. Very rarely there is temporary hair loss and skin erythema (reddening) that may occur a few weeks after the procedure. We make every effort to ensure the radiation dose is as low as possible.

  • . We are required by law to ask patients of childbearing capacity between the ages of 12 and 55 years about the possibility of pregnancy when undergoing examinations involving x-ray. In the urgent case of a thrombectomy, the procedure will most likely still go ahead but with additional precautions in place.


Are there any alternatives?

A thrombectomy is an emergency and potentially life-saving treatment performed in order to remove the blockage which is stopping blood flow to the patient’s brain. There is not often time to discuss alternatives in great detail due to the urgent nature of this procedure. An alternative to thrombectomy is the administration of a ‘clot busting’ thrombolytic drug. This is a less-invasive, but often not as effective, option. Some patients who are suitable for thrombectomy are not always able to have thrombolysis. This may be due to recent surgery or their individual increased risk of bleeding. It may also be due to the patient’s stroke onset time exceeding 4 hours and therefore being outside the thrombolysis time window.


What happens during the Mechanical Thrombectomy?

Most mechanical thrombectomy procedures at King’s College Hospital are performed under a general anaesthetic. Occasionally we will proceed with thrombectomy when your relative is awake but with a local anaesthetic.

The procedure is performed by an interventional neuroradiologist in the angiography suite (operating theatre) located in the neuroradiology department. A dedicated team of radiologists, radiographers, anaesthetists and nurses will be in the angiography suite to provide close monitoring throughout the procedure.

Once the procedure has started the doctor will place a thin, flexible, plastic tube (catheter) into the femoral artery. The catheter passes through the main artery in the body called the aorta and finally into the neck vessels and affected arteries in the brain. A second smaller catheter is inserted inside the first, and this goes directly behind the blood clot. Clot retrieval devices are then attached to this second catheter, and used to pull the clot out of the blood vessel. These devices may use suction or trap the clot inside a ‘stent retriever’. It may require multiple attempts to retrieve all the clot.

At the end of the procedure the catheters are removed and the blood vessel in the groin is sealed with a collaged plug called an ‘Angioseal’ .


How long does the procedure take?

It can take anything from 30 minutes to several hours.


What happens after the procedure?

After the procedure your family member will be transferred to a high dependency, advanced monitoring unit or recovery unit. After a stroke it is usually necessary to stay in hospital for days or even weeks for recovery.