Background readings: The CHADS2 & CHA2DS-VASc Stroke-Risk Grading Systems, and my 2015 AF Symposium reports: Dr. Hugh Calkins’ remarks on the AHA/ACC/HRS A-Fib Treatment Guidelines, and Dr. Peter Kowey’ talk, All Anticoagulants Cause Bleeding;
Current European guidelines for assessing A-Fib stroke risk state that a patient with a CHA2DS2-VASc score of 1 (on a scale of 0 to 10, no risk to high risk) should be taking novel oral anticoagulants (NOACs). But a recent Swedish study contradicts this.
A Swedish National Patient Registry study looked at 140,420 patients with A-Fib who had “stroke events”. For women with a score of 1, annual stroke rates varied between 0.1% and 0.2% (depending on which “event” definition was used). For men, the stroke rate varied between 0.5% and 0.7%.
The researchers stated, “These low annual event rates call into question the need for or use of oral anticoagulant therapy in these low-risk patients.”
Similar insights were found in a study of the National Health Insurance Research Database in Taiwan among 186,570 A-Fib patients not on antiplatelet or anticoagulant therapy. Researchers concluded that “not all risk factors in CHA2DS2-VASc score carry an equal risk.”
What this Means for A-Fib Patients
Taking an anticoagulant isn’t like taking vitamins. No one should be on anticoagulants unless they have an actual risk of stroke.
While the U.S. guidelines are an improvement over the European guidelines, based on the Swedish and Taiwan studies, neither the U.S. nor European guidelines recognize that someone with a score of 1 probably shouldn’t be on anticoagulants at all.
All anticoagulants cause bleeding (that’s how they work.) So they are inherently dangerous. Why run the risk if you don’t need to?
Taking an anticoagulant isn’t like taking a daily vitamin. No one should be on anticoagulants as a precaution, there should be an actual risk of stroke.
The Decision: To Take an Anticoagulant or Not?
When you have atrial fibrillation, whether or not to be on an anticoagulant to reduce your risk of stroke (and which one to take) is perhaps the most difficult decision for you and your doctor. That decision should be based on actual risk factors and not on a “precautionary” approach.
Remember, this decision means taking medication as long as you still have A-Fib. For some patients that’s a lifetime.
By Steve S. Ryan, PhD, Updated Nov 2014
In the US, doctors use what is called a CHADS2 stroke-risk grading system to help estimate the risk of stroke in patients with atrial fibrillation. A high CHADS2 score corresponds to a greater risk of stroke, while a low CHADS2 score corresponds to a lower risk of stroke. The CHADS2 score is simple and has been validated by many studies.
The patient’s stroke risk, i.e., their CHADS2 score, is estimated by adding together the points that correspond to the patient’s conditions.
“C” Congestive Heart Failure Score = 1
“H” Hypertension Score = 1
“A” Age over 75 Score = 1
“D” Diabetes Score = 1
“S2” Previous Stroke or TIA Score = 2
A CHADS2 score of 2 or over would indicate someone should be on a blood thinner such as warfarin.
The CHADS2 score has been superseded in clinical use by the CHA2DS2-VASc score that is designed to give a better stratification of low-risk patients. It utilizes the same 5 major risk factors considered by CHADS2 but assigns a score of ‘2’ for patients older than 75 years, and adds 3 new risk factors: a history of vascular disease, age 65-74 years, and female sex which increase stroke risk. But according to the original study, “there was no statistically significant difference found between the CHA2DS2-VASc and CHADS2 risk stratification schema in predicting TE events”.
A-Fib Stroke Risk Calculators
Classification of CHADS2 vs CHA2DS-VASc
In both scoring systems, a score of 0 is “low” risk of stroke, 1 is “moderate”, and any score above 1 is a “high” risk. The CHA2DS2-VASc system has three more variables and therefore will classify a greater number of patients into a high-risk group.
Editor’s comment: There is some controversy about the increased stroke risk for females. See articles on Dr. John M’s blog post and Aging Well magazine.
See also our article: Women in A-Fib Not at Greater Risk of Stroke, and The New CHA2DS2-VASc Guidelines and the Risks of Life-Long Anticoagulation Therapy.
Last updated: Thursday, September 3, 2015