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Atrial Fibrillation (cont.)

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Anticoagulation drugs to prevent blood clots and strokes

Atrial fibrillation is one of the most important causes of stroke in the U.S. warfarin (Coumadin) is a blood thinner that prevents the formation of blood clots. Studies in patients with chronic sustained AFib and sporadic (paroxysmal) AFib have shown that warfarin reduces strokes.

Aspirin is an antiplatelet agent. Platelets are elements in the blood that are necessary for blood clots to form. Aspirin can be considered a milder blood thinner than warfarin, but it is not as reliable as warfarin in preventing strokes in patients with AFib. Some doctors prescribe aspirin to patients when the risk of bleeding from warfarin is believed to be too high and to patients who refuse to take warfarin. It must be remembered that antiplatelet agents such as aspirin and clopidogrel (Plavix) are NOT as effective as warfarin in preventing stroke.

Side effects of warfarin

There are some patients who are at increased risk for side effects from warfarin. Specifically:

  • Patients with active stomach ulcers can develop ulcer bleeding while on warfarin.
  • Elderly patients can experience hemorrhage into the brain while taking warfarin. The risk of hemorrhage is higher if the patient also has high blood pressure.
  • Elderly patients who are unsteady and/or accident-prone are at an increased risk for trauma that can result in excessive bleeding.

Because of these serious side effects, patients using warfarin must be closely monitored with clotting tests such as the INR. The INR is a blood test that measures the degree of blood thinning (the higher the value for the INR, the thinner the blood). In preventing strokes in patients with AFib, the dose of warfarin is adjusted to achieve a "therapeutic range" of INR. INR values higher than the therapeutic range are associated with an increased risk for bleeding, while values below the therapeutic range are associated with a diminished effectiveness in preventing stroke. Patients who are unreliable or unwilling to be monitored with regular measurements of INR may be considered for aspirin treatment rather than warfarin.

The beneficial effect of warfarin in preventing strokes needs to be balanced against the risk of excessive bleeding if the blood becomes too thin.

Candidates for warfarin

Doctors recommend warfarin to most elderly patients 65 years of age or older with paroxysmal (recurrent episodes) or chronic sustained atrial fibrillation. On balance, elderly patients with atrial fibrillation are more likely to benefit from warfarin because they are at a particularly high risk for stroke.

Candidates for warfarin include patients younger than 65 with:

  • AFib (especially those with prior embolic strokes),
  • significant diseases of the heart,
  • diabetes,
  • high blood pressure,
  • heart failure,
  • coronary artery disease of the heart, or
  • abnormally enlarged atrial chambers.

Patients who are not candidates for warfarin

Patients who are not candidates for warfarin include:

  • patients with conditions that increase the risk of excessive bleeding, such as patients with active ulcers or other bleeding lesions in the intestines;
  • elderly patients who are unsteady and/or accident-prone and who are at an increased risk for trauma that can result in excessive bleeding; and
  • patients who are unreliable or unwilling to be monitored with regular INR measurements (for whom therapy with aspirin may be better).

Newer medications to prevent stroke

Newer antithrombotic agents that are as effective as warfarin in preventing strokes in patients with atrial fibrillation that do not require such intense monitoring or dietary restrictions include:

  • rivaroxaban (Xarelto),
  • apixaban (Eliquis), and
  • dabigatran (Pradaxa).

These antithrombotic agents work by a different mechanism from warfarin, and are suitable for many, but not all, patients. Indications should be discussed with the patient's physician.

Medically Reviewed by a Doctor on 5/4/2015

Source: MedicineNet.com
http://www.medicinenet.com/atrial_fibrillation/article.htm

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