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Stroke

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Description

An in-depth report on the causes, diagnosis, treatment, and prevention of stroke.

Alternative Names

Atrial Fibrillation; Transient Ischemic Attacks

Prevention

In 2002, the American Heart Association revised its guidelines for preventing heart disease, which include the following:

Improve Cholesterol. People with at least two risk factors and a 10-year risk for heart disease or stroke of more than 20% should aim for LDL levels of less than 100 mg/dl. Raising HDL levels is important for people at risk for stroke. Statins are now used in most cases.

Keep Blood Pressure Low. People in normal health should aim for 139/89 mm Hg or less. Patients with certain health problems, such as diabetes, should aim lower.

Exercise. Everyone in normal health should engage in at least moderate physical activity for a minimum of 30 minutes on most--if not all--days of the week.

Healthy Diet. Everyone should aim for a diet that contains a healthy balance of fruits, vegetables, grains, fish, nuts, legumes, poultry, lean meat, and low-fat dairy items. Avoid saturated fats and trans-fatty acids.

Quit Smoking. Also avoid exposure to second-hand smoke.

Maintain Weight. People should aim for a BMI index of 18.5 to 24.9. In people who are obese, reducing weight to this level can reduce the risk for stroke by 15% in men and 22% in women.

Taking Aspirin. People whose risk for heart disease within ten years is 10% or more should take a low-dose aspirin every day, unless they have medical reasons to avoid aspirin. It may also be helpful to prevent a second stroke, although it is unclear if it is helpful in preventing a first stroke, except possibly in patients with TIAs.

Control Diabetes. People with diabetes should aim for fasting blood glucose levels of less than 110 mg/dl and hemoglobin A1C of less than 7%.

Control Atrial Fibrillation. People with atrial fibrillation should use anticoagulants to reduce their risk of blood clots.

Diet and Weight Control

A healthy diet rich in fruits and vegetables and low in salt and saturated fats may significantly lower the risk for a first ischemic stroke. (The protective effects of diet on a second stroke are less clear.)

Fruits and Vegetables. Studies now suggest that individuals can protect their heart and circulation by eating plenty of fruits and vegetables. Eating such foods, according to a 2002 study, reduces blood pressure and protects against both heart attack and stroke. Important foods include most fruits (especially potassium-rich fruits including bananas, oranges, prunes, and cantaloupes) and vegetables (especially carrots, spinach, celery, alfalfa, mushrooms, lima beans, potatoes, avocados, broccoli). Vegetables, such as broccoli and kale, may be specifically protective against a first ischemic and possibly hemorrhagic stroke. Foods such as apples and tea, which are high in food chemicals called flavonoids, may also be very beneficial.

Whole Grains and Nuts. A 2000 study reported a lower incidence in stroke in women who had a high intake of whole-grain foods. Nuts may also be protective.

Calcium, Potassium, and Magnesium. Calcium, magnesium, and potassium serve as electrolytes in the body. They are important in controlling blood pressure and may also have protective effects against stroke:

Some evidence suggests that diets rich in potassium may protect against stroke by 22% to 40%, mostly by reducing blood pressure but also possibly because of other mechanisms. Low potassium levels may also increase the risk for stroke in certain people. In a 2000 study, potassium-poor diets were associated with a higher risk for stroke only in men with hypertension.

A major 1999 study reported that calcium intake is associated with a lower risk for stroke in women, which supports an earlier study reporting a lower risk for stroke in men who drank more milk.

Magnesium deficiencies may increase the risk for atrial fibrillation. No evidence yet exists, however, that taking magnesium supplements is protective.

Salt Restriction. Although the effects of salt restriction are not entirely clear, a 2002 study indicated that even a modest reduction in salt intake for more than month might reduce the risk of deaths from stroke by 14% in people with high blood pressure and 6% in people with normal blood pressure.

Fats and Oils The effects of fats and oils on stroke are complex. One study indicated that middle-aged men without heart disease who had the highest intake of monounsaturated or saturated fat (but not polyunsaturated oils) also had the lowest risk for stroke. Monounsaturated oils, obtained in olive and canola oils may have protective benefits against both heart disease and stroke. Saturated fats, found in animal products, are known risk factors for heart disease. Some studies suggest, however, that low intake of animal protein and saturated fats increases the risk of hemorrhagic stroke.

Other fat compounds that may be stroke protective are omega-3 fatty acids:

One form called alpha-linolenic acid is found in canola oil, soybeans, and walnuts. It has particular benefits against stroke by helping to prevent the formation of blood clots.
Omega-3 fatty acids are further categorized as docosahexaenoic (DHA) and eicosapentaneoic acids (EPA). They are found in oily fish and may be obtained in supplements. These compounds have anti-inflammatory and anti-blood clotting effects and may be significantly beneficial to the heart and reduce the risk for stroke.

Consuming fish two or three times a week, in any case, helps the heart and one study suggested that eating fish only one to three times a month protected against ischemic stroke. It should be noted that some studies have suggested that very high amounts (five or six servings weekly) of these fish can be harmful. A very high intake, for example, can increase the risk for a hemorrhagic stroke.

Vitamins

Folic Acid. The vitamin B, folate (usually in the form of folic acid) may protect against stroke. Studies have suggested that people who have higher blood levels of folate have a lower than average risk for stroke. Its primary benefit in this case appears to be to reduce levels of homocysteine, an amino acid that has been strongly linked to an increased risk of coronary artery disease, stroke, and Alzheimer's disease. A major 2002 study suggested that lowering homocysteine levels with folic acid would reduce the risk for heart disease by 16% and stroke by 24%.

Antioxidant Vitamins. The effects of antioxidant vitamins and carotenoids on stroke, dementia, or both have been studied. Studies are conflicting, however. A very important 2001 study reported no protection from stroke with vitamins A, E or beta carotene.

Caffeine Intake, Alcohol, and Smoking

Smoking. Everyone should quit smoking.

Alcohol. Mild to moderate alcohol use (one to seven drinks a week) is associated with a significantly lower risk for ischemic stroke, although not hemorrhagic stroke. Heavy alcohol use, particularly a recent history of drinking, is associated with a higher risk of both ischemic and hemorrhagic stroke.

Coffee. In healthy people with normal blood pressure, drinking a couple of cups of coffee a day is unlikely to do any harm. In fact, caffeine may have nerve-protecting properties that may help stroke survivors. Caffeine drinkers, however, might do better to choose tea, which may have beneficial nutrients, and people with existing hypertension should avoid caffeine altogether (since caffeine may increase the risk for stroke in this group).

Exercise

The benefits of exercise on stroke are less established than on heart disease, but a number of studies, including the following, suggest positive benefits:

According to one analysis of a group of 11,000 men, those who burned between 2,000 and 3,000 calories a week (about an hour of brisk walking five days a week) cut their risk of stroke in half. Groups who burned between 1,000 and 2,000 calories or more than 3,000 calories per week also gained some protection against stroke but to a lesser degree. In the same study, exercise that involved recreation was more protective than exercise routines consisting simply of walking or climbing.

Hypertension is a disorder characterized by chronically high blood pressure. It must be monitored, treated and controlled by medication, lifestyle changes, or a combination of both.

A 2000 study of women also found substantial protection from brisk walking or striding (rather than casual walking).

Reducing Blood Pressure

Reducing blood pressure is essential in stroke prevention. Life-style measures, such as exercise, weight loss if necessary, and healthful diets are important for everyone. Drug therapy is always recommended for people with hypertension where there is evidence that it is affecting the organs.

An important study in 2003 suggested that using low-doses of three different agents to lower pressure may reduce the risk of stroke by 63% and heart disease by half. Using low doses also reduces the risk for side effects.

Diuretics, the most effective agents for protecting against stroke, are also the least expensive. There are many brands and forms of this drug. Angiotensin converting enzyme (ACE) inhibitors, which include captopril (Capoten), ramipril (Altace), enalapril (Vasotec), quinapril (Accupril), are also important blood- agents, which may help prevent stroke even in high-risk patients with normal blood pressure. (Some experts believe, then, that both an ACE inhibitor and a diuretic should be given to patients with a history of stroke or TIA regardless of blood pressure.)

Other blood-pressure lowering agents that could be used in combinations are beta blockers and calcium-channel blockers.

[For more information on these agents, see the Well-Connected Report #14, High Blood Pressure.]

Statins and Raising HDL Cholesterol

Statins. HMG-CoA reductase inhibitors, commonly called statins, include as lovastatin (Mevacor), pravastatin (Pravachol), and simvastatin (Zocor). To date, statins are the most important cholesterol-lowering agents for protection against stroke and heart attack. According to a 2003 major analysis of over 200 studies, they reduce risk for heart events by 60% and stroke by 17%. Statins have nerve-protecting properties and some evidence suggests that taking statins may help stroke sufferers recover more quickly. More research is needed to confirm this.

Fibrates. Fibrates increase HDL (the good cholesterol) and reduce levels of triglycerides. They include gemfibrozil (Lopid), fenofibrate (Tricor), and bezafibrate (under investigation). In one trial, men with heart disease and low HDL levels had a 31% lower risk of ischemic stroke after taking gemfibrozil than did men who took a placebo. (These drugs may not provide the same benefits in people with higher HDL.)

[For more information on these agents, see the Well-Connected Report #23, Cholesterol, Other Lipids, and Lipoproteins.]

Influenza Vaccinations (Flu Shots)

There has been some evidence that influenza vaccinations might protect patients with a history of heart attack or heart events. A 2002 study further suggests that flu shots might protect against stroke, although possibly not in patients older than 75.

Atrial Fibrillation and Its Treatments

Treatment for atrial fibrillation always includes the use of agents (aspirin or warfarin, an anti-coagulant) to prevent clots from forming. One of two other approaches are available in addition to anticoagulants, either of which are effective in managing this disorder:

Restoring or maintaining normal heart rhythm. This is accomplished with anti-arrhythmic drug, cardioversions procedures, or surgery to remove the defective area.
Controlling heart rate. Specific drugs are used for this approach.

Important studies are reporting that controlling heart rate may be the preferable approach. In two 2002 studies, rhythm control offered no survival advantages and did not protect against ischemic stroke. Therapies aimed at controlling heart rate, furthermore, had fewer complications.

Drugs to Prevent Blood Clots

After a diagnosis of atrial fibrillation, warfarin (an anticoagulant) or aspirin is essential to prevent blood clots. When used correctly, these agents reduce the risk for stroke by over 60% in this patient group.

Warfarin (Coumadin, Panwarfin) is the agent of choice in preventing first and second strokes in high-risk patients with atrial fibrillation. Women with atrial fibrillation benefit more from warfarin than men. Unfortunately, one study reported that elderly women were half as likely to receive warfarin than men were. Warfarin carries a risk for bleeding and some physicians are reluctant to prescribe it in elderly people. Except for specific high-risk individuals however, the protection from warfarin far outweighs any danger for bleeding. Those at particular risk for bleeding are patients with a history of alcohol abuse, chronic kidney disease, or previous gastrointestinal bleeding.
Aspirin is less effective, but also has a lower risk for bleeding. It is highly protective, however, and the preferred treatment for younger people with atrial fibrillation and for people with no other risk factors for stroke, such as high blood pressure or diabetes. It may also be used by people at higher risk who cannot tolerate anticoagulation therapy.

Investigators are trying to develop other therapies that would be more effective than aspirin, but would not pose the high risk for bleeding that warfarin does. They include combinations of aspirin and other antiplatelet agents (e.g., dipyridamole and clopidogrel) and ximelagatran (Exanta), a new oral blood-thinning agent called a direct thrombin inhibitor.

Restoring and Controlling Heart Rhythm

To initially restore heart rhythm, anti-arrhythmic drugs are usually used first. If they fail to restore normal rhythm cardioversion is often effective. (Some experts suggest trying cardioversion first to avoid side effects of the drugs.) Long-term maintenance therapy using anti-arrhythmic drugs may be required.

Electrical Cardioversion. Electrical cardioversion is mild shock therapy and is the current standard treatment used to restore normal heart rhythm. It is conducted as follows:

Anticoagulants (drugs used to prevent blood clotting) should be administered, if possible, at least three weeks before the procedure.
During the procedure, the patient must be conscious and, although sedated, can experience some pain from the procedure.

Although the stabilizing effect is usually only temporary, some evidence suggests that a series of cardioversion may succeed in maintaining normal rhythm in young healthy patients without the need for antiarrhythmic medications.

Low-energy implanted cardioverters (e.g., Atrioverter, Jewel AF) are being investigated for maintenance. Studies are very promising.

Drugs Used for Maintaining Normal Heart Rhythm. For maintaining a stable rhythm, the following drugs may be used. The specific choices typically depend on whether the patient has existing heart disease or not:

For patients with no heart disease, the first choices include sotalol, flecainide, or propafenone, which are often used sequentially. If these fail, then amiodarone or a newer agent dofetilide (Tikosyn) may be tried. Others include ibutilide (Covert), and azimilide. If these agents are not effective, than other drugs tried include quinidine, procainamide, and disopyramide.
In patients with heart disease, amiodarone, dofetilide, or sotalol are commonly used depending on the cause of heart disease.

Amiodarone is more effective than most others and has been thought to be safer than many other similar drugs. Even in low doses, however, there is a high incidence of side effects, including thyroid disorders, neurologic, skin, and eye problems, and abnormally slow heart beats. Many of these drugs carry a small but significant increased risk, however, for a life-threatening arrhythmia called torsades de pointes and should be avoided by people with certain heart conditions.

Surgical Procedures for Complex AF. In some difficult cases, surgery may be recommended. The options and candidates depend on other complicating factors. The following are some examples:

AV node ablation involves severing the communication between the atria (the two upper chambers of the heart) and the ventricles (the two lower chambers). A pacemaker is then implanted just under the skin with electrodes leading to the ventricles. This approach is very effective, but it is irreversible and must be used life-long. Radiofrequency ablation may be an option in some patients.
A more aggressive procedure uses open chest surgery, in which a maze of cuts is made in the atria. As they heal, the scar tissue prevents the heart circuitry from misfiring. It controls atrial fibrillation in more than 90% of appropriate candidates. A new procedure is similar but less invasive.

Controlling Heart Rate

Drugs Used to Control Heart Rate. Drugs used to control heart rate are beta-blockers (such as propranolol) or calcium channel blockers. Digitalis, an older drug, is not used as often but is proving to be very effective in combination with the other agents. These agents are used to reduce heart rate at the onset of atrial fibrillation.

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