~Stroke and Cerebrovascular Disease, Part 2
What You Have Learned So Far...
Warning Signs of Stroke (NINDS 2005)
- Stroke is the third-most-common cause of death in Americans, caused by blood clots blocking the flow of blood supplying oxygen to the brain or by hemorrhage in the blood vessels of the brain. One in four men and one in five women over the age of 45 will suffer a stroke.
- The most common risk factor is high blood pressure.
- An ischemic stroke occurs when the blood flow to the brain is disrupted because of a blood clot. A hemorrhagic stroke occurs when the blood flow to the brain is disrupted by a ruptured artery. Ischemic strokes account for about 80 percent of strokes.
- Ischemic strokes are closely associated with atherosclerosis and underlying endothelial dysfunction in the arteries. Any treatment that improves endothelial health may help lower the risk of a stroke.
- Stroke results in more long-term disabilities in the United States than any other disease.
- If a stroke is suspected, it is essential to get emergency medical care as soon as possible.
- Preventive measures can reduce the risk of having a stroke or a second stroke.
Stroke Screening: Advances in Technology
- Sudden weakness, numbness, or paralysis of the face, arm, or leg, particularly on one side of the body
- Sudden confusion or loss of speech or understanding of language
- Sudden loss of vision in one or both eyes
- Sudden severe headache with no apparent cause
- Sudden dizziness, loss of balance or coordination, or trouble walking
Although transient ischemic attacks are the most obvious warning signs of stroke, the risk of having a stroke can be gauged before an ischemic attack occurs. All that is required is diagnostic testing. Clearly, it is preferable to avoid a stroke through early intervention and preventive measures than to treat strokes that have already occurred.
In the past, the most accurate test to measure atherosclerosis was angiography. During this procedure, a catheter is threaded into the arteries and a special dye sensitive to x-ray is injected into the catheter. While this is an important test, it has some powerful limitations. First, it is invasive and therefore not practical as a widespread screening tool. Second, it can show the physician only the shadowy outlines of plaque inside arteries. It cannot measure the stability of the plaque or determine the health of the arterial wall.
Today, noninvasive imaging techniques are available to measure the health of the arterial wall and even determine the stability of the plaque deposits on the inside of the artery. Although these tests are most often used to diagnose existing strokes, they are also highly effective screening tools.
Advanced CT scanners, including a newly introduced 64-slice machine, are able to provide an unprecedented view of the arteries. No studies have yet been conducted on the value of this new technology in screening people for stroke risk. Older, 16-slice CT scanning is often recommended to evaluate the damage of ongoing strokes because of its specificity (Kirchhoff K et al 2002). CT scans, however, expose people to very high levels of radiation. For example, an average CT head scan exposes the body to as much radiation as 100 chest x-rays, or 243 days of natural background radiation, according to the European Commission’s Radiation Protection Report, conducted in 2000.
Perhaps the most widely used screening tool for stroke is the carotid ultrasound, which provides physicians with valuable information on the health of carotid arteries. Using widely available and relatively inexpensive ultrasound technology, physicians can detect the degree of blockage in the carotid arteries and measure the thickness of the intima-media. The well-known Rotterdam study showed that if carotid intima-media thickness is greater than 1 mm, the risk of stroke is increased even if no arterial plaque is present (Hollander M et al 2003). The information obtained from ultrasound screening can be used to identify people at high risk of atherosclerosis.
A number of blood tests also measure vascular health and may help identify people at high risk of stroke. Life Extension believes that people should have at least annual blood tests for homocysteine, C-reactive protein, and fibrinogen, in addition to the more well-known tests, such as those for cholesterol and triglycerides. Homocysteine, C-reactive protein, and fibrinogen each have been shown to be elevated among people at risk of stroke.
Reducing Homocysteine to Lower Stroke Risk
At the 2001 meeting of the American Stroke Association, researchers reported studies showing that increasing levels of homocysteine are associated with elevated stroke risk. One of these presentations was a meta-analysis of 15 published studies and showed that mild to moderate elevations in homocysteine were independently associated with an astounding 86 percent increase in the risk of stroke (Kelly PJ et al 2000).
Folic acid and other B vitamins help decrease homocysteine concentrations. The metabolism of homocysteine has been linked to several vitamins, but particularly folic acid (folate), B6, and B12 (Schwammenthal Y et al 2004). The Vitamin Intervention for Stroke Prevention trial, among many studies, showed that homocysteine levels decreased and risk of stroke, death, and other coronary events fell by 21 percent in patients who received high doses of vitamin B12 (Spence JD et al 2005).
Another well-designed study found that giving B vitamins within 12 hours of an ischemic stroke reduced oxidative damage and the tissue inflammation marker C-reactive protein, regardless of homocysteine levels (Ullegaddi R et al 2004). Studies have also found that vitamin B6 alone is strongly associated with lower risk of cerebrovascular disease (Kelly PJ et al 2003).
Other studies show that individuals with homocysteine levels elevated by 25 percent have increased risk of stroke of 11 percent. A meta-analysis of 20 studies reported that elevated homocysteine levels increased risk of ischemic heart disease by 32 percent and risk of stroke by 59 percent (Wald DS et al 2002). Multiple studies have shown folate to prevent endothelial dysfunction even in people with normal levels of homocysteine, high cholesterol, diabetes, and heart disease (Moat SJ et al 2004), which emphasizes the importance of the B vitamins (He K et al 2004, Bazzano LA et al 2002).
C-Reactive Protein and Fibrinogen
There is a clear association between elevated levels of C-reactive protein and fibrinogen and the incidence and severity of stroke. Also at the 2001 American Stroke Association meeting, researchers presented evidence that elevated C-reactive protein doubled or tripled the risk of stroke (Kelly PJ et al 2000). Another presentation showed that in those who have a major stroke, higher levels of C-reactive protein portended a high likelihood of having another vascular event, such as a heart attack or stroke, or of dying within the following year. Stroke patients with the highest C-reactive protein levels were nearly 2.4 times more likely to experience death or a vascular event within the next year than were patients with the lowest levels (Di Napoli N et al 2001).
Similarly, the Physician’s Health Study found that apparently healthy men with the highest C-reactive protein levels had twice the risk of stroke, three times the risk of future heart attack, and four times the risk of future peripheral vascular disease (Ridker PM et al 1997). The Women’s Health Study reported that C-reactive protein was the single strongest predictor of future vascular risk (Ridker PM et al 1998).
Elevated levels of fibrinogen are also associated with increased risk of stroke. Fibrinogen is a protein produced by the liver. It circulates in the blood and helps stop bleeding by helping blood clots form. Today’s standard laboratory reference range for fibrinogen is between 193 and 423 mg/dL. That means according to conventional standards, fibrinogen levels as high as 423 mg/dL are acceptable.
However, a study reported in the Journal of the American Medical Association found that no matter what a patient’s level was within the range tested (between 250 mg/dL and 562 mg/dL), an increase of 100 mg/dL was associated with a significantly increased risk of heart disease and stroke (Danesh J et al 2005). Another study found that those with high fibrinogen levels, above 343 mg/dL, had a twofold increase in the risk of heart attack (Ma J et al 1999). Fibrinogen levels can be reduced by taking dietary supplements such as fish oil and vitamin C and by lowering homocysteine.
Responding to a Stroke: Speed Matters
Most of the damage from a stroke occurs within 24 hours following the event, so it is crucial that people get adequate treatment as fast as possible to reestablish blood flow and limit the damage. If stroke-like symptoms last for more than 10 to 15 minutes or worsen, call 911 without delay even if it is unclear whether a stroke has occurred (NINDS 2005).
Once a patient has arrived at the hospital, physicians will quickly seek to determine what kind of stroke (ischemic or hemorrhagic) occurred, then take steps to treat it. Diagnostic imaging tests are usually performed as soon as possible to determine the kind of stroke.
Treatment of ischemic stroke. The goal of acute therapy in ischemic stroke is to dissolve the blood clot as rapidly as possible (a process called lysis). Studies show that when thrombolytic (clot-busting) agents are administered within three hours of symptom onset, they can dramatically decrease damage (Burger KM et al 2005). These drugs are still effective if given within 4.5 hours of the stroke (Davalos A 2005). Unfortunately, however, most stroke patients do not receive the appropriate thrombolytic agent quickly enough (Burger KM et al 2005; Davalos A 2005).
The most common thrombolytic agent used is tissue plasminogen activator. It is typically administered intravenously, and newer methods using ultrasound-enhanced delivery promise to make this drug even more effective (Davalos A 2005).
After stroke, there is a significant risk of a repeat stroke. To help prevent secondary strokes, people may be prescribed anticoagulant therapy, including low-dose aspirin or long-term warfarin (Coumadin®) therapy, or antiplatelet therapy (such as Plavix®).
Treatment of hemorrhagic stroke. Acute treatment of hemorrhagic stroke focuses on surgery and medications. Surgical procedures can help alleviate the damage (hematoma), but the condition of the patient before surgery is critical to the recovery rate. People who are conscious and have small blood clots often improve without surgery. But people in comas, who have large clots, do very poorly, regardless of treatment approach (National Stroke Association 2005)
- Anticoagulants. These drugs work by preventing clot growth or preventing new clots from forming. Warfarin is the most common example. It is often used when a patient’s doctor suspects that a blood clot has originated in the heart and traveled to the brain and lodged in a vessel, blocking blood flow and causing an embolic stroke. Anticoagulants are not indicated when there is increased risk of bleeding or in patients with uncontrolled high blood pressure (NINDS 2005).
- Antiplatelet agents. Antiplatelet agents work by preventing blood platelets from sticking to each other and forming a clot. Common examples are aspirin, dipyridamole, and clopidogrel. They are also often used to reduce the risk of stroke in individuals who have had a transient ischemic attack or to decrease the risk of a second ischemic stroke.
After the acute treatment, medications may be prescribed to control blood pressure, which is a major risk factor for hemorrhagic stroke (Clarke CRA 1998). Prescription medications for lowering blood pressure include diuretics, calcium channel blockers, beta blockers, ACE inhibitors, and others. For more information on natural ways to lower blood pressure, see the chapter titled High Blood Pressure.
Stroke prevention is a subject of much debate. Approximately 25 percent of people who recover from a first stroke will have a second within five years. While the chance of death and disability increases with each stroke, risk of another stroke appears to be greatest within the first year (National Stroke Association 2005).
Using measurements such as the degree of artery occlusion (how much of the carotid artery is blocked by atherosclerotic plaques), medical experts have sought to establish firm guidelines to help physicians choose between the various options, including medication, angioplasty, and surgery. Common prescription drugs used to help prevent stroke include antihypertensive agents (Gorelick PB et al 1999; Goldstein LB et al 2001), cholesterol lowering agents (statins), and antiarrhythmics to help control irregular heartbeats that might contribute to stroke risk. Angioplasty is a procedure in which a balloon is threaded into the artery and inflated rapidly, crushing the plaque against the arterial wall and opening the artery. The most common surgery used to prevent stroke is called carotid endarterectomy, in which the surgeon opens the arteries in the neck and strips away the inner lining of the artery.
While these strategies have been shown to work in specific circumstances, a common flaw also unites them: they are often used only after stroke risk has reached an unacceptable level. Life Extension prefers a much more proactive approach. By using advanced early screening tests to determine risk, then taking action to improve endothelial function and reduce blood risk factors (such as homocysteine and fibrinogen) and blood pressure, Life Extension seeks to maintain the lowest possible risk profile.
Diet. Multiple studies have found that a diet high in fruits and vegetables lowers risk of cerebrovascular disease and both ischemic and hemorrhagic stroke (Gariballa SE 2000; Sauvaget C et al 2003). Two major reviews recommended that public health policy promote increased dietary intake of antioxidant vitamin C, beta-carotene, vitamin E, B vitamins (including folate), potassium, calcium, magnesium, vitamin D, fiber, and omega-3 fatty acids to reduce risk of stroke (Gariballa SE 2000; Johnsen SP 2004). These vital nutrients can also be obtained through dietary supplements in conjunction with a healthy diet.
Continued . . .
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