Prediction of ischemic stroke:
A CHADS2 score is the most accurate tool for prediction of stroke in patients with atrial fibrillation (65). Calculating a CHADS2 score uses the following scoring system (129):
- 2 points for previous stroke or TIA (transient ischemic attack)
- 1 point for recent CHF (congestive heart failure)
- 1 point for hypertension
- 1 point for age 75 years or older
- 1 point for diabetes
Rate of stroke by CHADS2 score:
The rate of stroke occurrence without anticoagulation per year depends upon the CHADS2 score as follows (65):
- CHADS2 score of 0: 1.9% per year.
- CHADS2 score of 1: 2.8% per year.
- CHADS2 score of 2: 4.0% per year.
- CHADS2 score of 3: 5.9% per year.
- CHADS2 score of 4: 8.5% per year.
- CHADS2 score of 5: 12.5% per year.
- CHADS2 score of 6: 18.2% per year.
Treatment for prevention of ischemic stroke in patients with atrial fibrillation:
- The patient’s cardiologist and primary care provider are responsible for recommending treatment for the prevention of stroke. According to the American Heart Association/American Stroke Association (AHA/ASA) basic treatment guidelines are as follows (64):
- CHADS2 score of 0: No treatment or aspirin is recommended.
- CHADS2 score of 1: Antithrombotic therapy choice by the physician varies.
- CHADS2 score of 2 or higher: Anticoagulation is recommended for atrial fibrillation to prevent stroke.
Warfarin, aspirin, and clopidogrel use in risk of stroke:
Warfarin with dose changes to maintain therapeutic range reduced the risk of stroke in atrial fibrillation from an average of 4.5% to 1.4%. Aspirin reduces the risk of stroke in atrial fibrillation by about 21%. Benefit verses risks of bleeding or adverse effects from anti-thrombotic therapy should be discussed in detail with the physician. The risk of severe bleeding episodes while taking warfarin was about 1.3% per year, and with aspirin, about 1% per year. Therapy with both aspirin and clopidogrel were demonstrated to be about the same severe bleeding risk as warfarin with a small reduction in stroke rates.