Stroke Response


Endovascular Management of Ischemic Stroke

by Matthew Tenser, MD, neurologist

 

Knowing your care options in advance for stroke patients is essential in optimizing outcomes. Many acute stroke patients are not candidates for IV tPA. Endovascular stroke therapies should be considered for acute stroke patients who have failed or are not eligible for IV tPA.

 

Stroke is the leading cause of disability and the third leading cause of death in the United States. Approximately 800,000 people suffer a stroke each year, resulting in over 140,000 deaths. It was estimated that over $73 billion were spent on stroke-related medical costs and disability in 2010.

 

The natural history of intracranial large vessel occlusive disease is particularly poor, with morbidity and mortality rates over 90 percent, depending on the affected vessel. Intravenous tissue plasminogen activator (IV tPA), the only widely available FDA-approved treatment for ischemic stroke, has been shown to be efficacious in recanalization of occluded intracranial vessels and improvement of clinical outcome. In 2007, a meta-analysis of more than 50 studies involving 2,000 acute stroke patients revealed an overall recanalization rate of 46 percent with IV fibrinolysis. Studies have shown, however, that the overall frequency of recanalization is lower for large vessel occlusions. Reported rates range from 29 percent to 55 percent in the middle cerebral artery (MCA), 30 percent to 80 percent in the vertebrobasilar (VB) system, and from 6 percent to 14 percent in the internal carotid artery (ICA).

 

 

Matthew Tenser, MD

 


Case Study:
Treatment for Acute
Large Vessel Occlusion >>


Many acute stroke patients are not candidates for IV tPA, as eligibility is restricted by medical contraindications and stringent exclusion criteria. A narrow time window and inadequate public awareness of stroke symptomatology and urgency further limit the number of patients who may benefit from this therapy.

 

It is estimated that only 3 percent to 10 percent of those patients eligible for IV tPA actually receive the drug.

 

Endovascular stroke therapies should be considered for acute stroke patients who have failed, or are not eligible for, IV tPA. Intra-arterial (IA) tPA administration decreases the undesired effects of systemic infusion and allows for direct delivery to the region of maximal clot burden, but is limited to six hours of symptoms or less. Mechanical revascularization establishes vessel patency via clot extraction, providing an alternative treatment for those who are not eligible for, or fail, thrombolytics.

 

The same meta-analysis described above demonstrated a 63 percent overall recanalization rate for IA thrombolysis and an 83 percent revascularization rate for mechanical therapy. Revascularization was significantly associated with good functional outcome, defined as a modified Rankin Score (mRS) =2 (58 percent mRS =2 for recanalized patients versus 25 percent with no recanalization), and lower mortality (14 percent versus 41 percent).

 

At this time, there are two FDA-approved devices for endovascular treatment of acute ischemic stroke. These are the Merci Retrieval System, which uses a corkscrew-shaped device to engage and remove the clot, and the Penumbra System, which uses a catheter to aspirate the clot. The Penumbra device is indicated for use in patients with symptoms for eight hours or less. While the Merci retriever was approved for use without a time window, many physicians use eight hours as the maximum time limit for treatment based on initial mechanical thrombectomy studies. However, the traditional dogma that eligibility for endovascular stroke therapy should be limited by strict temporal criteria is being challenged.

 

Recent reports suggest that penumbral imaging and perfusion mismatch may supplant time since symptom onset as the principal selection criteria for revascularization, and many stroke centers are using imaging in addition to time of symptom onset to determine eligibility for endovascular treatment. Several randomized controlled trials (RCT) are ongoing to attempt to clarify the role of endovascular stroke treatment. Two examples are:

•  The MR and Recanalization of Stroke Clots Using Embolectomy (MR RESCUE) trial is a RCT comparing best medical care versus endovascular therapy for large vessel occlusions with symptoms less than 8 hours, and to determine if diffusion and perfusion MR imaging can identify patients who may benefit from recanalization.
•    The Interventional Management of Stroke (IMS) III trial is a RCT comparing full dose IV tPA versus a 2/3 dose of IV tPA plus endovascular therapy in patients with large vessel occlusions.

 

Because so few acute stroke patients are eligible for IV tPA, the information gained from these and future studies is vital. Positive results help expand the treatment window and therapeutic options for a devastating disease.  

 


 

Case Study:
Stroke Treatment for Acute Large Vessel Occlusion

 

A 72-year-old woman with a history of atrial fibrillation was admitted to the hospital for surgical repair of cervical disc disease. She was taking Coumadin prior to hospitalization, and was treated with therapeutic doses of Lovenox when the Coumadin was held for surgery. She was seen in the intensive care unit (ICU) at 6 p.m. the evening before her planned procedure at her normal, non-focal neurologic baseline.

 

During a routine nursing check at 7 p.m., she was found to be lethargic with a global aphasia, right homonymous hemianopsia, left gaze preference, and complete loss of strength and sensation on the right. Her NIH Stroke Scale score was 25. A computed tomography (CT) scan of the head and CT angiogram (CTA) of the head and neck were performed (see figures 1A, B).

 

Once it was determined that the noncontrast head CT did not have any evidence of hemorrhage, the patient was temporarily taken out of the scanner and given IV tPA. After the bolus was given and infusion was started, the patient was returned to the scanner to compete the imaging. Imaging revealed no significant parenchymal changes to suggest a completed infarct. The CTA revealed an occlusion of the proximal M1 segment of the left middle cerebral artery (MCA).

 

Once the imaging was completed, the patient was re-examined and demonstrated no clinical improvement. Since she had no response to the IV thrombolytics, had no significant changes on CT to suggest completed infarct, and had a large vessel occlusion on the CTA, she was felt to be a candidate for endovascular stroke therapy.

 

After a discussion of the poor natural history of the lesion, as well as the risks of the procedure, consent was obtained from the family who felt that she would want every possible option of treatment considered.

 

 

 

 

 

The patient was taken to the angiography suite, and the procedure began at 8:20 p.m. Initial angiography confirmed the presence of the proximal MCA occlusion and poor collateralization to the left MCA territory (see figure 2).

 

Based on her arterial anatomy and clot location, the Penumbra System was chosen for recanalization therapy. After only a few minutes of clot aspiration, angiography revealed complete recanalization of the proximal MCA lesion and reperfusion of the distal MCA territory without any distal emboli (see figure 3).

 

She was returned to the ICU for the remainder of her stroke care. By the next morning, she had only mild word-finding difficulties. She was back to her normal neurologic baseline within two days, and had successful spine surgery one week later.

 

 


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