Mechanical thrombectomy: a revolution in the treatment of ischemic stroke

Mechanical thrombectomy is an innovative and effective technique in the management of certain acute ischemic strokes. It is also called “endovascular treatment of ischemic stroke”. The term thrombectomy, for its part, means “to remove the clot” (the same one which “occludes” or obstructs a large artery in the brain).

Ischemic stroke: what exactly is it?

Cerebrovascular accident (CVA) is a serious illness, which causes a neurological deficit linked to brain lesions of vascular origin. Each year in Europe, around 150,000 people suffer from it: the blood is no longer able to properly irrigate the brain either because an artery is blocked (ischemic stroke or cerebral infarction, which represents 80% of cases); either because there is a hemorrhage (hemorrhagic stroke, due to a rupture of a cerebral blood vessel, which represents 20% of cases).

When the obstruction of the cerebral artery resolves on its own and does not cause any after-effects, it is called a transient ischemic attack (TIA). “Its symptoms are the same as stroke, but they last from a few seconds to a few minutes before returning to normal, are not painful and can, therefore, be trivialized or minimized. However, TIA can precede stroke: particular vigilance must therefore be taken by patients who report its symptoms.notes Dr Raphaël Blanc, radiologist, deputy head of the interventional neuroradiology department at the Adolphe de Rothschild Foundation Hospital, in Paris.

Stroke is the 3rd cause of death in Europe (40,000 people die from it each year). It is also a major cause of disability, generating serious after-effects and leading to intellectual decline. On average, the number of strokes increases by 5% each year and affects all age groups (early childhood to old age, with a greater frequency after 50 years). “Its most common causes are: disorders or morphological abnormalities of the heart rhythm and problems of atheroma (or atherosclerosis, that is to say arterial obstruction or narrowing (carotid stenoses), caused by risk factors cardiovascular: high blood pressure, smoking, lack of physical activity, hypercholesterolemia, etc.)”explains the specialist.

Since 2015, however, mechanical thrombectomy has revolutionized the management of ischemic strokes related to the occlusion of a large artery (artery 1 to 6 mm in diameter): the effectiveness of this interventional radiology procedure, carried out urgently, has been demonstrated by several international studies.

Mechanical thrombectomy and stroke: what does this brain intervention consist of?

Mechanical thrombectomy is the acute treatment of ischemic stroke (occlusion of a large artery in the brain). It is carried out urgently – often at night or on weekends – by neuroradiologists specialized in interventional radiology. This medical technique, carried out in an operating room under local or general anesthesia, consists of unblocking the cerebral artery or vein responsible for the infarction in order to restore blood circulation to the brain. “This is one of the greatest emergencies that can exist, because this action must be carried out as quickly as possible. As soon as we have the diagnosis, the intervention is initiated.”continues the radiologist.

This obstruction affects the supply of oxygen and nutrients, which can damage brain cells (sudden neurological deficit, loss of speech, loss of strength on one side of the body, coma – more rare – etc.). The after-effects of a stroke depend on the part of the brain that has suffered damage and the extent of the damage. The quicker we intervene, the more we allow the brain to have access, as quickly as possible, to the blood necessary to function normally: we thus limit the possible after-effects that the stroke could leave. Scanner and MRI help to locate exactly the point of cerebral occlusion.

In practice, it therefore involves inserting a catheter into the femoral artery (at the level of the groin fold), then going up through the arteries to the blocked brain artery to fetch – with a probe – the thrombus or clot responsible for the occlusion with a device that is then removed (stent retriever). Once this clot is fragmented, extirpated or aspirated, blood circulation resumes normally.

Deadline for using it

This treatment is carried out by a specialized team, either in addition to intravenous thrombolysis or alone in the event of a contraindication to thrombolysis. It is possible to use it up to 6 hours after the stroke, or even more. “The delay can actually extend up to 24 hours after the start of symptoms, in some cases. It is the imaging performed that decides on the intervention. We are increasingly trying to offer this intervention to everyone. Particularly when people have to be transferred to an expert center, it necessarily takes more time”notes Dr Raphaël Blanc.

Thrombectomy is also used in the treatment of femoro-iliac deep vein thrombosis (all of the femoral and then iliac veins, themselves at the origin of the inferior vena cava).

Be careful, do not confuse thrombectomy and embolectomy (surgical procedure which consists of removing a circulating foreign body (embolus) or a substance obstructing a blood vessel). Embolus, a more general term than thrombus, can in fact designate a substance other than the blood clot (for example, cholesterol, fat, gas, etc.).

“Similarly, we must distinguish thrombectomy from intravenous thrombolysis (or fibrinolysis), which is the drug treatment of stroke and which consists of injecting a fluidifier capable of dissolving the clot which blocks the artery of the brain and causes the cerebral infarction. The two treatments are often combined.adds the specialist.

When to do a thrombectomy?

Mechanical thrombectomy is recommended in the first hours, if the cerebral infarction is due to occlusion of a large artery (internal carotid artery, middle cerebral artery, basilar trunk). It is recommended in the acute phase of stroke, up to 6 hours after the onset of symptoms in patients.

How exactly does it take place in detail?

Thrombectomy consists of introducing, under fluoroscopic control, a catheter through the femoral artery and tracing it up to the blocked artery in the brain. The procedure takes place under local or general anesthesia, depending on several criteria (patient's condition, impaired consciousness, agitation, etc.). The sooner it is performed, the less risk of permanent damage to the brain.

Once the patient is transported by the emergency services to a dedicated unit, he is placed in the operating room. The thrombectomy then involves several stages.

• Preliminary examinations: blood sample collection; weighing the patient (to determine the exact dosage of medications that will be administered); electrocardiogram (ECG) to measure the activity of the heart; capillary blood glucose aimed at determining the blood sugar level; brain CT or brain scan, MRI, to measure the extent of the stroke and locate the clot blocking the artery;
• Procedure: Once the intervention is confirmed, the patient is brought to the angiography operating room for the thrombectomy, then prepared for local anesthesia (in the vast majority; simple sedation controlled by the anesthetist) or general anesthesia. The catheter is then introduced into the groin (or at the level of the arm) – under fluoroscopic control – and directed towards the intracranial arteries passing at the level of the aorta and the neck (carotid). In general, this gesture is not painful. A nickel-titanium net located at the end of the catheter deploys and hooks the clot which is then extracted from the body (this procedure is what we call thrombectomy stricto sensu). “We can also aspirate it or put in place a small stent to recover this clot. Often, we resort to a combination of the two”, observes the radiologist. Once the check has been carried out, the catheter is removed and the puncture point closed.
• Surveillance : Once the procedure is completed, the patient is placed in intensive care, under surveillance for at least 24 hours. All its constants are monitored (blood pressure, pulse, breathing, temperature, etc.), as well as neurological signs (checking the condition of the pupils, strength and the feeling of weakness in the arms and legs) .

In the case of deep vein thrombosis, thrombectomy is performed using an intravenous device introduced transcutaneously. Its principle is the same: it involves introducing a catheter equipped with a specific mechanism into a vein located away from the thrombosis…