ASPIRIN TO PREVENT HEART ATTACK AND STROKE

Abd Khatib, MD, FACC
Cardiology
Eau Claire Heart Institute
Eau Claire

The medical community supports taking an aspirin on a regular basis if one has had a heart attack, unstable angina, stroke or has been diagnosed as being high risk for coronary problems. The question then becomes what’s the right dose?

In preventing heart attacks and strokes we have to understand two elements: aspirin and platelets. Aspirin, or acetylsalicylic acid, was first introduced in the 1890s as a treatment for a variety of inflammatory conditions. It was not until almost 70 years later that its blood thinning or antiplatelet effect was recognized and later still that it was studied for the treatment of coronary artery disease or hardening of the arteries (also called cholesterol plaque).

Platelets are blood cells that respond to damaged vessels or arteries to seal the surface area and form a platelet plug. The plug may progress to form a blood clot that can lead to a heart attack that could be fatal.  When there is a high cholesterol level in the blood, hardening of arteries or cholesterol plaque will form in the lining of the arteries.  Arteries are then weakened and a small tear in the lining of the artery may occur.  This is called plaque rupture.  Platelets will rush in to seal the area and repair the damage to the lining of the artery by sticking to the area and sealing the damaged surface.  This is called platelet aggregation.  This reduces the size of the artery diameter, consequently blood flow to the heart muscle decreases leading to heart pain or angina.

Aspirin exerts its blood thinning effect by reacting with a platelet enzyme called cyclooxygenase (irreversibly acetylating the enzyme cyclooxygenase (COX).  Platelets are the first blood cells that respond to stop bleeding or react to tissue injury.  Aspirin’s major anti-clotting effects and clinical utility derive from decreasing overall platelet accumulation at the site of the thrombus or clot.  Aspirin inhibition of COX is permanent; and thus its anti-clotting effect lasts for the life of the platelets, usually 7 to 10 days.  That means the blood thinning effect of aspirin and its use for patients with heart disease comes from its reaction with the platelet enzyme that makes the platelets more slippery or less sticky at the site of cholesterol build up and plaque rupture.  Aspirin will help to stop a blood clot from forming, or at least reduce its size, which will stop or decrease clogging the artery with blood clot and may avert heart attack and relieve angina.

In one study, it was observed that aspirin-treated patients free of known coronary artery disease, but with one or more of the following: hypertension, diabetes, obesity, family history of premature heart attacks (MI), or advanced age had lower incidence of cardiovascular death and total cardiovascular death, non-fatal MI, non-fatal stroke, angina, transient ischemic attack (TIA) or mini-stroke, peripheral artery disease or revascularization procedure. Unfortunately, severe bleeding occurred more frequently in the aspirin group than in the placebo or non-aspirin group.

The American Heart Association guideline for the primary prevention of cardiovascular disease recommends the use of low dose aspirin (75 to 160 mg daily) in persons at increased risk for coronary artery disease, especially those with a ten-year risk of more than 10 percent.

Patients should discuss with their physicians the use of aspirin to understand the benefits and risks.  The incident of minor bleeding, however, appears to be dose related.  A dose of 160 mg. a day probably provides the best balance between therapeutic effectiveness and bleeding risk.

For more information on heart health and aspirin or to schedule an appointment with Dr. Khatib, Eau Claire Heart Institute, call 715.831.4444