Atrial Fibrillation (cont.)
Anticoagulation to prevent blood clots and strokes
AF 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 AF and sporadic (paroxysmal) AF
have shown that warfarin reduces strokes.
Aspirin
is an anti-platelet 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 AF. 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. Young patients with lone AF who are not at an increased risk for
stroke sometimes are given aspirin rather than warfarin.
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 AF, 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 AF. On balance, elderly patients with AF are more likely to
benefit from warfarin because they are at a particularly high risk for stroke.
Patients younger than 65 with AF, especially those with prior embolic
strokes, significant diseases of the heart, diabetes mellitus, high blood
pressure, heart failure, coronary artery disease of the heart, or abnormally
enlarged atrial chambers also are candidates for warfarin.
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
- Patients who are unreliable or unwilling to be monitored with regular INR
measurements (for whom therapy with aspirin may be better)
Next: Converting atrial fibrillation to a normal rhythm »
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