Endovascular Stroke Treatments

There's More Than One Way to Bust A Clot

An ischemic stroke is caused by a blood clot that lodges in one of the arteries of the brain, cutting off precious blood supply to brain tissue. Every minute that a stroke goes untreated, almost two million brain cells die. That's 14 billion synapses and 7.5 miles of myelinated fibers gone every minute. It is critical that stroke be treated as soon as possible.

For over a dozen years, the only FDA-approved therapy for acute stroke was IV administration of recombinant tissue plasminogen activator (tPA, alteplase).

This must be given within 4.5 hours after the symptoms of a stroke first come on. The tPA breaks up the clot, restoring blood flow to the brain.

Unfortunately, there are many situations in which tPA cannot be used, and so relatively few people receive this treatment. Interest is growing in other methods of breaking down or removing blood clots that stick in the brain's blood vessels to cause stroke. The most common alternative methods are neurointerventional stroke therapies.

What Is Neurointerventional Stroke Treatment?

A neurointerventionalist is someone who uses advanced radiographic imaging techniques and long, thin catheter tubes to access part of the body that would otherwise be difficult to reach. The tubes are threaded through the body’s blood vessels, usually from an opening in the femoral vessels near the groin. From there, it is possible to reach all the way into the brain. This is known as an endovascular approach (endo = within, vascular = blood vessel).

These endovascular techniques can be helpful in acute stroke. A powerful drug like tPA can be administered right where the clot has blocked an artery. This is known as intra-arterial thrombolysis or endovascular thrombolysis.  Another endovascular option in acute stroke is to use a mechanical thrombectomy device to remove the clot.

These therapies can be provided by qualified interventional radiologists, neurosurgeons, and neurologists.

What is Intra-Arterial Thrombolysis?

The main medication that is used by most physicians for intra-arterial thrombolysis is tissue Plasminogen Activator (tPA). However, the technique was first tested with a medication that is now uncommon—prourokinase. The data showed a 15% benefit to people who received intra-arterial (IA) prourokinase, but there was also a higher intracerebral hemorrhage rate.

IA thrombolysis is usually done in a situation in which IV thrombolysis has failed. However, some people have proposed following an IV dose of thrombolytics with an intra-arterial dose as well. Initial results suggested that this procedure was safe, however, a trial of this combination procedure was stopped. At this point, intra-arterial thrombolysis is predominantly used in people who are not candidates for IV tPA, but who present within six hours of the time their symptoms began.  

However, more recent results suggest that other approaches, which make use of mechanical thrombectomy devices, may be safer and more effective.


What Are The Different Types of Mechanical Thrombectomy Devices?

There are several devices that are FDA approved to remove blood clots. The first was the Merci Retriever device (Concentric Medical, Inc; Mountain View, CA), which looks like a corkscrew. The end of the device screws into a clot in order to permit clot removal. Anotherdevice is the Penumbra System (Penumbra, Inc; Alameda, CA), the tip of which functions something like a vacuum for the clot. Yet another is the Solitaire FR Revascularization Device ev3 Endovascular, Inc., Plymouth, MN), which slips a wire mesh around the clot for retrieval.

All of the devices have been shown to remove blood clots from the brain of someone having a stroke. Generally, it seems that the MERCI device may be less effective than others.  When in doubt, the most important thing is probably the comfort and skill of the neurointerventionalist with any particular clot retrieval device.

Are There Any Tests Needed Prior to These Interventions?

Some people suffering from acute stroke may respond better to these endovascular procedures than others. A common method of investigating whether someone may benefit is to use neuroimaging techniques like CT scans and MRI. Special protocols can be used to look at how blood is flowing into brain tissue. The idea is to try to determine if there is a region of brain, called penumbra, that is at risk of further damage, but that could be saved if blood flow was restored.

There are three imaging methods that can guide the selection of stroke patients: noncontrast computed tomography (NCCT), computed tomography perfusion (CTP) and magnetic resonance imaging (MRI) diffusion-weighted imaging (DWI) mismatch. None is clearly better than the others. NCCT is fast, but not as accurate as other methods in predicting the size of the penumbra. An MRI scan that measures something called diffusion weighted imaging mismatch is the most accurate method, but takes a long time, and during a stroke, time is very important. CT perfusion is between the previous two.

The techniques of endovascular clot retrieval in acute stroke are relatively new, and the precise role for these techniques is still being developed. However, it is important to realize that even if someone is unable to receive tPA for some reason, there may still be a way to restore blood flow to the brain if they reach the hospital quickly. There is a saying in neurology that "time is brain." Getting to a hospital immediately if you notice any signs of stroke could prevent serious disability or death.


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