Preventing Another Stroke

Until now, we have discussed ways to prevent having a stroke. If one already suffered a stroke, the risks for another stroke are much higher than the general population. This is because (for the most common types of strokes), the same risk factors for stroke have already had such a profound effect that a stroke already occurred. This makes it all the more likely that the blood vessels are already sufficiently compromised and another stroke is likely. The risk for a recurrent ischemic stroke (non-bleeding) in those who do not use pharmacologic prophylaxis is roughly 10% for the first year after a stroke and 5% per year after that.  

So, how do we prevent the next stroke?   

First, it is important to categorize strokes into different types, because the different types have different medications indicated for stroke prevention.  

There are two major types of strokes. The first is ischemic (non-bleeding), and the second is hemorrhagic (bleeding). The ischemic strokes require blood thinners to prevent another stroke, while the hemorrhagic cannot use blood thinners (in the short-term), since this will make the bleeding stroke worse.  

Ischemic strokes can be further broken down into four types: thrombotic, thromboembolic, lacunar, and embolic. It is important to realize that the common feature in all ischemic strokes is that an artery that supplies the brain is blocked by a blood clot. This blockage is what causes the stroke.  

Of these four types of ischemic strokes, there are basically two categories: thrombotic and embolic. The first category, thrombotic, is comprised of three different types:

1. Thrombotic
2. Thromboembolic
3. Lacunar

 

In thrombotic strokes, the blockage occurs locally. A blocked blood vessel is damaged and a platelet plug forms (mostly comprised of a type of blood cell known at platelet). This plug gets so large that it completely blocks the artery and causes a stroke.  
 

Insert Image Here

In thromboembolic strokes, the same platelet plug forms on an area of arterial wall damage. The platelet plug does not get large enough to completely block the artery where it forms, but a piece of this plug, or the entire plug, can break off and flow downstream. As it flows downstream, the circumference of the artery gets smaller. The plug eventually settles in smaller artery (where the inner circumference of the artery matches the size of the platelet plug). The area of the brain supplied by the smaller artery has a stroke.   

In lacunar strokes, the mechanism is similar, but it occurs in extremely small arteries. The exact mechanism is beyond the scope of this discussion. It is important to note, however, that these strokes are also caused by blood clots.  

The important common feature in all three of these types of strokes is that they are caused by platelet plugs, and therefore, are treated with antithrombotic or antiplatelet agents.  

The second class of ischemic strokes is known as embolic strokes. These are caused by blood clots that form, for the most part, in places other than arteries supplying the brain. Places such as the left atrium of the heart (in atrial fibrillation), the left ventricle of the heart (in people with heart damage), or veins (as in deep vein thromboses [DVT]), that travel through a heart defect (patent foramen ovale (PFO)), to the artery supplying the brain. Again, the mechanism of these strokes is less important. The important thing is to realize that in all these cases, the clots are formed in places other than the arteries supplying the brain. These clots are usually not made up of platelets. For this reason, other medications known as anticoagulants (usually warfarin or Coumadin), are needed to prevent future strokes.  

Hemorrhagic or bleeding stroke is a much less common type of stroke. Because these strokes occur when there is bleeding, blood thinners cannot be used in the short-term. However, the same risk factors that caused the bleeding stroke, puts this person at risk for a future stroke, which very well may be a non-bleeding stroke. It is for this reason that one should stay in close contact with a neurologist or stroke specialist to determine when and if a blood thinner should be started after a bleeding stroke.  

Once you know which type of stroke you have had and you know which medication is needed, there are a few different choices.  

Antithrombotic (antiplatelet) medication. In those with an ischemic, non-embolic stroke (category 1), antithrombotics or antiplatelet agents are recommended. There are three general classes of medications in this category:

1. Aspirin
2. Thienopyridines. There are 2 medications available in this group (clopidogrel or Plavix) and (ticlopidine or Ticlid).
3. A combination of extended release dipyridamole and aspirin combination known as Aggrenox.

 

All three of these types of medications work by limiting platelet aggregation, reducing the risk of formation of the platelet plug.  

The first line of treatment for anyone with this type of stroke should be aspirin. It has, by far, the most research done on it, and has proven effectiveness in the reduction of future strokes. Although the exact dose is unclear, it should be approximately 75-325 mg (approximately one baby aspirin to one regular aspirin). Aspirin itself can cause bleeding. This bleeding, most commonly is either intracranial (inside the head, like bleeding stroke) or gastrointestinal (bleeding in the stomach or intestines). By using the above-mentioned doses of aspirin, risks of these events are limited and the benefits of stroke reduction are still realized. The risk/benefit ratio strongly favors the use of aspirin for secondary stroke prophylaxis in most people. Aspirin is also the cheapest and most widely available of these medications, and in general, is regarded as the medication of choice.  

In those who are allergic to aspirin or had a stroke despite taking aspirin, or have other reasons for not using aspirin, the thienopyridines are another alternative. In this group, Plavix is used almost exclusively nowadays, as its safety profile is more favorable than Ticlid. Plavix also blocks platelet aggregation and platelet blood formation, and prevents stroke by that mechanism..  

There is ongoing research on using aspirin and Plavix in combination. The theoretical advantage of using both of these medications is that aspirin and Plavix both thin the blood by affecting platelets through different mechanisms. The theory was by decreasing the “stickiness” of platelets in two locations instead of one, the risk of stroke would be further reduced.  

The last category of antiplatelet medications is the combination medication made up of extended release dipyridamole and aspirin, known as Aggrenox. This can be used in those who had a stroke despite taking aspirin, but have no reason to avoid aspirin itself (no allergies or gastrointestinal bleeding).  

Both Plavix and Aggrenox are significantly more costly than aspirin, thereby posing a greater financial burden on the healthcare system as a whole and to the consumer in particular.  

In patients with the second category of ischemic stroke (the embolic stroke), in general anticoagulants like warfarin (Coumadin) are the treatment of choice for long-term stroke prevention. When taking warfarin, regular blood testing is required to make sure the blood is “thin enough,” but not “too thin.” This testing is not required when taking the antithrombotic medications.  

There are other lifestyle and medication changes that should be made in all people who have had a stroke, and especially in those with a hemorrhagic stroke or those who have strokes despite being on proper blood thinning medication.  

Blood pressure: Once you have a stroke, literature seems to indicate that lower blood pressure can significantly lower your risk of a recurrent stroke. This even applies to people who do not have what is classically considered elevated blood pressures.  

Although it is likely that any class of blood pressure medication probably works, most literature was performed using either a thiazide diuretic (type of water pill) or a class of medications called ACE inhibitors (your doctor will be familiar with both of these terms.)   

How much should your blood pressure be lowered? 

This is not clear. There is evidence that the lower the blood pressure, the better off you are (assuming the low blood pressure does not cause side-effects). Most will aim for approximately a blood pressure of`120/70. In those with mostly or completely blocked blood vessels in the neck and head, one should be cautious while lowering blood pressure and the patient should be followed closely by a physician.  

Cholesterol: There is good evidence that the class of cholesterol lowering medications known as statins is extremely beneficial in preventing recurrent strokes. Interestingly, it seems to be beneficial no matter how high or low your pre-stroke cholesterol levels were. Those whose cholesterol levels remain extremely elevated even with treatment should see a specialist. These medications rarely cause liver or muscle problems. If symptoms occur, you should contact your doctor to perform appropriate lab work after stopping the medication.  

Diabetes mellitus: Although there is no proven evidence that careful blood sugar control reduces the risk of recurrent strokes, it definitely reduces other complications from diabetes mellitus and probably does favorably reduce the risk of stroke.  

In this population there should be extra attention to using all of the modalities mentioned above and below to reduce the risk of stroke.  

Vitamins: People with elevated homocysteine levels seem to be at high risk for stroke. Elevated homocysteine levels can be lowered with supplementation of folic acid and Vitamin B12. It is unclear if this actually lowers the risk of recurrent stroke or not. Since both of these medications are relatively inexpensive and benign, there appears to be no harm in using them.  

There is also, as of yet, no evidence that other antioxidant vitamins (such as Vitamin C, Vitamin E, and beta carotene) will lower the risk of recurrent stroke.  

Hormone replacement therapy (in females): It is not useful in preventing recurrent strokes and probably is detrimental. Unless there is significant reason to continue hormone replacement therapy, it should be stopped after a stroke.  

Tobacco: It is very hard to do, but tobacco use should be stopped. This applies to all forms of tobacco. Whether done cold turkey, with the assistance of medications, or nicotine replacement and/or counseling, tobacco use should be stopped.  

Diet: Intuitively diets low in fat, high in fruits and vegetables, generous in oily fish and unsaturated fats, and low in sodium are what seem to be beneficial. There are no good studies confirming this.  

Exercise: Exercise should be encouraged in those who are able to exercise after a stroke. The exact amounts of exercise should be discussed with your doctor.  

Alcohol intake: It is very difficult to study the effects of alcohol on recurrent stroke, but those with no alcohol intake or very high alcohol intake have higher rates of stroke than those with moderate intake (approximately two drinks per day). Those who drink a lot should cut back. Those who drink a little can continue to drink moderate amounts (approximately two drinks a day).