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Options in the Care of Acute Ischemic Stroke

Understanding stroke means understanding options in the care and treatment of the disease. Planning ahead by recognizing the symptoms and understanding the treatment options and where they are offered may benefit you and your family.

In ischemic stroke, the blockage is usually caused by a clot, also called a thrombus or embolus. The primary goal in treating ischemic stroke is to restore blood flow to the brain. This can be done by removing the clot, dissolving the clot or by otherwise disrupting the blockage that is occurring in one or more vessels in the brain. Clinical data confirm that restoring blood flow to the brain correlates with improved outcomes and increased chance of survival for ischemic stroke patients. Clots may or may not respond to drugs, or pharmaceutical options. Based on the patient’s symptoms, the blockage location, and other diagnostic testing, the treating physician will decide the best and safest method for treating a stroke.

Clot Dissolving Drugs
Merci Retrieval
Stenting or Balloon Angioplasty
Aspiration of Clot

If diagnosis occurs within 0 to 3 hours from the onset of symptoms, your physician may administer Activase also referred to as IV tPA or Intravenous tissue Plasminogen Activator. Activase was FDA approved for the treatment of acute ischemic stroke in 1996. In Europe, as well as in some U.S. centers, protocols have been extended to allow for treatment with IV tPA up to 4.5 hours from the onset of symptoms. Though not officially FDA approved in the U.S., the time window expansion is supported by a highly regarded clinical study published in 2008 and by a scientific advisory council recommendation.

Activase is part of a family of drugs called lytics, or clot busters, and is usually given intravenously through a vein in the arm. If the clot is of average or small size, the drug may be successful in dissolving the clot completely. In large vessel stroke, the size of the clot (clot burden) may be too big for the drug to be effective and the patient may require additional intervention. Some patients may not be eligible for IV tPA due to serious illness, recent surgery, clotting disorders or other conditions. Sadly, since most patients do not reach the hospital before 3 hours, only 3 to 4% of those who suffer an acute ischemic stroke actually receive this treatment.^1,2,3 In these cases, other treatments may be necessary.

Lytic medication may also be infused directly into the clot through a minimally invasive surgical or endovascular procedure. The term endovascular (within the vessels) refers to types of procedures that are performed using vessels in the body to access the treatment site. In this procedure, a small incision is made in the femoral artery in the upper leg, and a catheter (small tube) is threaded into the artery where the clot is lodged. The lytic medication is then passed through the tube and into the clot. This procedure may be done alone, or may be performed as adjunctive treatment, meaning in combination with another endovascular attempt to disrupt the blockage or retrieve the clot. IA lytic infusion is usually performed within 6 hours of the onset of a patient’s symptoms. While this option is not FDA approved, it has become widely accepted by physicians and physician societies as an option in acute ischemic stroke care.

As with any surgery, endovascular procedures involve risks that include but may not be limited to: infection, vessel perforation or puncture with or without subsequent bleeding or worsening of symptoms, vessel dissection, and even death. The primary risk associated with lytic agents is hemorrhage or bleeding in the brain. The NINDS trial found that this occurred in 6.4% of patients who were given an IV (intravenous) infusion of the drug within 0 to 3 hours of symptom onset.⁴ The other consideration with infusion of IV tPA is the effectiveness of the drug on clots of varying size. Some studies suggest that smaller clots tend to respond more favorably to this therapy, while larger clots may require additional intervention. In large vessel strokes, the recanalization rate of those that were eligible to receive IV tPA, has been shown to be approximately 33%.⁵ For patients taken to the angiography lab, the rate of restoring blood flow when lytic was infused directly into the clot in a commonly affected blood vessel (Middle Cerebral Artery) was reported to be 66% vs. 18% for those who did not receive the medication. Other, larger vessels of the brain were not studied for this therapy and may require more aggressive treatment.

The Merci Retrieval Procedure is an endovascular procedure using the Merci Retriever to mechanically remove the clot. If a patient does not respond to lytic therapy (using a clot-busting agent) or if they are ineligible for the drug (either due to medical conditions or arrival to the hospital after 3 hours from experiencing symptoms), the treating physician may suggest this surgical option. The Merci Retriever is a minimally invasive, catheter-based device that was cleared by the FDA in 2004 to restore blood flow in the brain by removing clots in patients experiencing an ischemic stroke. The Merci Retriever is used in the larger vessels of the brain, and has been used up to 8 hours past the start of symptoms, and sometimes longer, based upon physician discretion.

The Merci Retriever is a tiny corkscrew or spring-shaped device that works by wrapping around the clot and trapping it. The clot is then retrieved and removed from the body. Over 14,000 patients world wide have undergone this procedure and it has been performed at over 500 U.S. hospitals. Not all hospitals perform the Merci Retrieval Procedure.

As with any surgery, the Merci Retrieval Procedure is not without risk. Endovascular procedures are a minimally invasive form of surgery and risks include: infection, vessel perforation or puncture with or without subsequent bleeding or worsening of symptoms, vessel dissection, and even death. Acute stroke is an emergency situation and decisions often must be made quickly. A treating physician can further explain the risk and benefits involved with the Merci retrieval procedure.

Clinical data show a strong correlation between restoring blood flow to the brain and better overall outcomes for stroke patients. This means that those who have blood flow restored are more often functioning independently and with less disability. Restoring blood flow is a principal goal when treating ischemic stroke patients. In the Multi MERCI trial, the Merci Retriever restored blood flow in 55% of patients when used alone, and 68% of the time when used in conjunction with IA lytic. For every 3 patients treated with the Merci Retriever, blood flow was restored in approximately 2 patients, and of those 2 patients, one had little or no disability. Specifically, of the patients who had blood flow restored, 49% were functioning independently at their 90-day follow up with the doctor.⁶In the Merci Registry, an extensive collection of cases in which the Merci Retriever was used, the revascularization rate is approximately 77% overall⁷.

This endovascular procedure involves inflating a small balloon to crush the clot against the artery walls. While not FDA approved for the treatment of acute ischemic stroke, this option has been used to successfully restore flow in the occluded vessel in certain cases. A stent may also be placed to hold clot or plaque against the wall after balloon angioplasty if there is evidence of atherosclerotic disease (i.e. the build-up of plaque on the vessel wall). If a patient has plaque occluding a vessel, a physician may recommend this treatment in the context of a clinical study, as it is still being investigated for acute stroke treatment.

In this endovascular procedure, the physician delivers a catheter through the vessels to the affected area of blockage and attempts to aspirate the obstruction using suction. This procedure has not been studied in as many patients as the Merci Retrieval procedure, but it has been found to be effective and some devices are FDA cleared. As with any surgery, this procedure is not without risk. Endovascular procedures are a minimally invasive form of surgery and risks include infection, vessel perforation or puncture with or without subsequent bleeding or worsening of symptoms, vessel dissection, and even death. Acute stroke is an emergency situation and decisions often must be made quickly. A treating physician can further explain the risks and benefits involved with this type of procedure.

References
1.Kleindorfer D, Lindsell C, White G, et al. National US Estimates of rtPA Use: ICD-9Codes Substantially Underestimate. Stroke 2006;37(2):621-2.
2.Reeves MJ, Arora S, Broderick JP, et al. Acute stroke care in the US: results from 4 pilot prototypes of the Paul Coverdell National Acute Stroke Registry. Stroke 2005;36(6):1232-40.
3.Reeves MJ, Broderick JP, Frankel M, et al.The Paul Coverdell National Acute Stroke Registry: initial results from four prototypes.Am J Prev Med 2006;31(6 Suppl 2):S202-9.
4.National Institute of Neurological Disorders and Stroke rt-PAStroke Study Group. Tissue plasminogen activator for acute ischemic stroke.N Engl J Med 1995;333:1581-1587.
5.Saqqur M, et al. Site of arterial occlusion identified by transcranial Doppler predicts the response to intravenous thrombolysis for stroke.Stroke. 2007 Mar;38(3):948-543.
6. Smith WS., Mechanical Thrombectomy for Acute Ischemic Stroke, Final Results of the Multi MERCI Trial.Stroke2008; Apr;39(4):1205-1212.
7. Data on file at Concentric Medical, Inc.

APM0527_A_4343, 2010-08