Modifying Risk Factors

Major risk factors for stroke include high blood pressure, diabetes, cigarette smoking, heavy alcohol use, physical inactivity, and high cholesterol levels. Treating these risk factors can help prevent both first stroke and recurrent strokes. If you have had a transient ischemic attack or stroke, the time for action on these risk factors is now. There can be no more dilly-dallying. Use diet and exercise, and medications if needed, to control your blood pressure. Never smoke again. Drink alcohol only moderately, if at all-no more than one to two drinks per day. Perform a continuous physical activity, such as walking briskly, for 30 minutes a day, at least three days a week. Adopt a diet low in cholesterol and saturated fats and use cholesterol-lowering medicines if needed, to control your cholesterol levels.

Atrial Fibrillation and Cardioembolic Stroke

About one in four ischemic strokes are cardioembolic. They are due to clots forming in the heart and then breaking off and traveling to the neck or head to block blood vessels that nourish the brain. A variety of abnormalities of the heart can cause a clot to form, including a recent heart attack, dilated cardiomyopathy (stretching and poor pumping action of the heart chambers), disorders of the heart valves, and atrial fibrillation. These conditions generally cause blood flow to slow down in parts of the heart, and whenever blood slows it tends to clot. For this reason, a common treatment to prevent further strokes in someone who has had a cardioembolic stroke is the powerful anticoagulant (anticlotting) medicine warfarin.

Atrial fibrillation is the most common heart condition that causes stroke. In atrial fibrillation, the upper chamber of the heart has disorganized electrical activity. The muscles in the upper chamber do not act together to produce pumping contractions, but instead act at random, causing the wall to wriggle without contracting. Blood flow tends to slow down in this non-beating chamber, and so clots tend to form. The anticlotting medicine warfarin can decrease the chance that clots will form and thereby decrease the chance of stroke. Individuals who have had an ischemic stroke or transient ischemic attack should generally be treated with warfarin, unless they have a strong contra-indication to its use like recent surgery, bleeding disorders, or dementia.

Warfarin is sometimes called a blood-thinner, but this term is somewhat misleading. Warfarin doesn't actually alter the thickness or the oxygen-carrying capacity of the blood, or lower the number of blood cells. Instead, it decreases the tendency of the blood to form clots. The chief risk of warfarin is that it will increase the chance of bleeding-into the brain, into the gut, or elsewhere. For this reason, the anticlotting action of warfarin needs to be monitored with a blood test, at least once a month. When used carefully, with regular monitoring, the risk of bleeding with warfarin is very low and the benefit in preventing cardioembolic stroke is very high.

Atherothrombotic Stroke and Medications

Atherothrombotic strokes are the result of cholesterol plaque buildup in large blood vessels in the neck and head (atherosclerosis) or thickening and cholesterol plaque buildup in small blood vessels within the brain substance itself (lacunar stroke). The irregular surfaces on the blood vessel walls disrupt the flow of blood and activate platelets-clumping elements in the blood. Platelets that clump together can cause further blockage of blood vessels, leading to a stroke. Antiplatelet medications are drugs that block the clumping together of platelets, and they reduce the risk of stroke, heart attack, and death after a first atherothrombotic stroke or transient ischemic attack.

Four different antiplatelet medications are of proven benefit for preventing recurrent stroke and/or heart attack in individuals with a first stroke.

Aspirin: Aspirin is the tried and true antiplatelet agent. It is very inexpensive and it is effective. Aspirin does have both occasional minor side effects (such as stomach upset) and uncommon major side effects (bleeding, ulcers), but these are generally outweighed in the ischemic stroke patient by its benefit in preventing additional strokes or heart attacks. The current recommended dose of aspirin for stroke prevention is from 50 to 325 milligrams a day.

Clopidogrel: Clopidogrel prevents platelet clumping through a different molecular pathway than aspirin. Clopidogrel is more effective than aspirin in preventing stroke, heart attack, or death in patients with atherosclerotic vascular disease. Clopidogrel is generally a very safe medication, with few side effects. It causes diarrhea slightly more often than aspirin, but causes bleeding from the gut slightly less often than aspirin.

Dipyridamole and Aspirin: Dipyridamole prevents platelet clumping through a different molecular mechanism than either aspirin or clopidogrel. Combining slow-release dipyridamole and aspirin is more effective than using aspirin alone to prevent recurrent stroke in patients who have had a first ischemic stroke or a transient ischemic attack. Pills are available that contain a combination of aspirin plus slow-release dipyridamole. Dipyridamole is generally a very safe medication. The most common minor side effects are headache or stomach upset.

Ticlopidine: Ticlopidine prevents platelet clumping through a molecular mechanism similar to that of clopidogrel. Ticlopidine is more effective than aspirin in preventing recurrent stroke in patients with a stroke or transient ischemic attack. However, the side effects of ticlopidine are more common (rash or diarrhea) or more worrisome (bone marrow suppression) than with other antiplatelet medications. Because of these side effects, ticlopidine is used less frequently than in the past.

Warfarin: Warfarin in an anticoagulant medication that prevents clotting by preventing clotting proteins from joining together. Warfarin is no more effective than aspirin in preventing atherothrombic stroke, and requires regular monitoring blood tests. For this reason, it is only infrequently used to prevent recurrent atherothrombotic stroke (in contrast to its important role in preventing recurrent cardioembolic stroke).

Carotid Artery Disease and Carotid Endarterectomy

A common site that atherosclerosis builds up and causes stroke is in the origin of internal carotid artery in the neck. An individual is said to have symptomatic carotid artery stenosis if they have narrowing of the internal carotid artery due to atherosclerosis and they had an ischemic stroke or transient ischemic attack in the regions of the brain to which blood is supplied by the internal carotid artery.

Treatment options for patients with symptomatic carotid artery stenosis include a surgical procedure called carotid endarterectomy. In a carotid endarterectomy, a surgeon makes an incision in the skin of the neck, dissects down to the diseased artery, surgically opens the artery, removes the plaque, and then sews the artery up again. The surgery is most often performed with the patient asleep under general anesthesia, but occasionally may be performed with the patient awake under regional or local anesthesia. The surgery takes about 60 to 90 minutes to perform, and patients are generally able to go home one to two days after surgery.

Surgery risks
Like all surgical procedures, there is a risk of adverse outcomes with carotid endarterectomy. In good surgical hands, the risk of a major adverse outcome (stroke or death) from carotid endarterectomy in a patient with symptomatic disease is up to three to six percent. However, in many individuals the risk of not having the surgery and having another stroke from their carotid artery blockage is much higher. The decision to proceed with surgery or to stick to conservative medical treatment must be tailored to the individual patient, taking all their risk factors into account. Age, coexisting heart disease, other systemic illnesses, and many other variables should be considered. A critical variable is the degree of carotid artery narrowing. The more severe the narrowing, the higher the risk that the carotid blockage will cause another stroke unless it is removed by performing surgery. When the narrowing is severe (between 70 to 99 percent), surgery is the preferred approach, unless a patient has strong contraindications. When the narrowing is moderately severe (50 to 69 percent), there tends to be a moderate benefit of surgery in most patients. In the less moderately narrowed group (30 to 49 percent), there is no definite benefit of surgery over medications in general, although select patients likely do benefit from surgery. In the mildly narrowed group (less than 30 percent), medications without surgery is generally the preferred initial treatment strategy.

Patients with a complete, 100 percent carotid occlusion are a special case. Generally after the carotid artery becomes completely blocked, blood pooling in the vessel forms a large clot along the entire length of the artery. At this point, a carotid endarterectomy is no longer possible, because a massive operation would be needed to clean out the entire carotid artery along its whole course through the neck and the skull.

Conclusion

One stroke is more than enough. The chances of experiencing another stroke can be dramatically reduced by taking appropriate actions. All individuals with a first stroke or transient ischemic attack should vigorously control their blood pressure, diabetes, and cholesterol, moderate their alcohol intake, stop smoking, and exercise regularly. Most individuals with atrial fibrillation should begin regular treatment with warfarin. Individuals with atherothrombotic stroke should begin regular treatment with antiplatelet medications. Individuals with carotid artery stenosis should undergo evaluation for carotid endarterectomy. By taking these simple steps, stroke survivors can substantially reduce their risk of another brain attack.