Aspirin Therapy (Guidelines for Heart Attack and Stroke Prevention)

  • Medical Author:
    Omudhome Ogbru, PharmD

    Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.

  • Medical Author: Daniel Lee Kulick, MD, FACC, FSCAI
    Daniel Lee Kulick, MD, FACC, FSCAI

    Dr. Kulick received his undergraduate and medical degrees from the University of Southern California, School of Medicine. He performed his residency in internal medicine at the Harbor-University of California Los Angeles Medical Center and a fellowship in the section of cardiology at the Los Angeles County-University of Southern California Medical Center. He is board certified in Internal Medicine and Cardiology.

  • Medical Editor: Jay W. Marks, MD
    Jay W. Marks, MD

    Jay W. Marks, MD

    Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

When is aspirin used for preventing and treating heart attacks and strokes?

Aspirin is widely used either alone or in combination with other antiplatelet agents to prevent blood clots from forming in arteries. Aspirin is used specifically in several situations including:

  1. Aspirin often is prescribed in moderate doses (160-325 mg/day) for people who are having heart attacks to limit the extent of damage to the heart's muscle (by preventing further blood clot formation in the blood vessels of the heart and reduction of blood flow), prevent additional heart attacks, and improve survival.
  2. Aspirin often is prescribed to patients undergoing surgery to open or bypass blocked arteries, including percutaneous transluminal coronary angioplasty (PTCA) with or without placement of coronary stents and coronary artery bypass surgery (CABG). Aspirin also is prescribed on a long-term basis to prevent clotting in the stents and/or the bypassed blood vessels.
  3. Aspirin often is prescribed in low doses (75-160 mg/day) on a long-term basis to patients with prior heart attacks or strokes and to patients with TIAs (transient ischemic attacks or mini-strokes) and exertional angina to prevent heart attacks and ischemic strokes.
  4. Aspirin is prescribed in moderate doses (160-325 mg/day) to patients who are having unstable angina to prevent heart attacks and improve survival.
  5. Aspirin is prescribed in moderate doses (160-325 mg/day) to selected patients who are having ischemic strokes to limit damage to the brain, prevent a second stroke, and improve survival.

Aspirin for treatment of heart attacks

In a large multi-center study (Second International Study of Infarct Survival of the ISIS-2 trial) of patients having acute heart attacks, early treatment (within 24 hours of the onset of symptoms) with aspirin (160 mg/d) was found to reduce deaths from the heart attacks by 23%. The improved survival is believed to be due to aspirin's ability to quickly prevent further blood clots and the extension of existing clots and thus limit the amount of damage to the heart's muscle.

Aspirin is easy to use, safe at the low doses used for its antiplatelet action, and fast acting. Aspirin at moderate doses (160-325 mg/day) produces an antiplatelet effect rapidly (within 30 minutes). The current recommendation is to give aspirin immediately to almost all patients as soon as a heart attack is recognized at a dose of 160-325 mg/d and to continue it for one month. The only reason for not using aspirin is a history of intolerance or allergy to aspirin or evidence of obvious active bleeding (such as actively bleeding stomach ulcers) that might be worsened by aspirin.

Performance of vascular procedures

Aspirin is not the only treatment for heart attacks and unstable angina. Sometimes percutaneous transluminal coronary artery angioplasty (PTCA), with or without placement of an arterial stent, is necessary to open narrowed or blocked coronary arteries. In rare instances, PTCA may be technically impossible, or not practical, to do, and coronary artery bypass graft surgery (CABG) becomes necessary to improve the flow of blood to the heart.

Some patients with heart attacks also may be treated with thrombolytic agents (medications that dissolve clots) to open blocked arteries. It is important to make the distinction that aspirin generally does not dissolve an existing blood clot, but it acts to prevent propagation of the existing clot and the formation of new ones. In all of these instances, there is a risk that blood clots will form again inside the arteries, leading to further heart attacks. In all of these cases, aspirin has been shown to be beneficial in preventing new clots, thus reducing the risk of heart attacks and improving both short and long-term survival.

Prevention of further heart attacks

There are two types of heart attack prevention, primary and secondary. Preventing the first heart attack in people who do not have a history of heart disease is called primary prevention. Preventing further heart attacks among patients who already have had a heart attack or another heart related condition is called secondary prevention.

Within six years after the first heart attack, 16% of men and 35% of women will have a second heart attack. Long-term, daily aspirin (75-325 mg/d) has been shown to reduce the risk of second heart attacks and improve survival among both men and women. Additionally, long-term secondary prevention with aspirin also has resulted in fewer ischemic (lack of blood flow due to blockage in blood vessels from clot formation) strokes. Therefore, survivors of heart attacks usually take daily low dose (75 mg-160 mg/d) aspirin indefinitely to prevent further heart attacks as well as strokes.

Aspirin taken long-term is an important part but NOT the only measure for preventing heart attacks. Aspirin is not recommended for primary prevention of heart attacks because available evidence does not support its use for primary prevention.

Medically Reviewed by a Doctor on 10/24/2016

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