Many of my patients question the recommendation of taking an oral anticoagulant (blood thinner) when they have been given the diagnosis of atrial fibrillation. The most common discussion is the risk of stroke by not taking the medication vs. the risk of bleeding taking the medication.
This has always been a very complicated decision making process in atrial fibrillation. I am writing this to share with all of you that I don’t arbitrarily just prescribe drugs. Taking care of a patient and the decision making that goes into each patient is complex and individual. The tools that we as physicians have to use to make our decisions are complex. So I thought I would give you a glimpse into the complexities regarding “guidelines” for treatment with anticoagulation in atrial fibrillation.
Back when I was in cardiology training in the late 70’s / early 80’s, the text books would state that if the patient was in atrial fibrillation for longer than 48 hours, then warfarin (Coumadin) should be started.
Over the years, that time frame gradually shrunk down to the point that when atrial fib lasted longer than 12 hours, we would consider initiating therapy.
Over the past 8 years, “decision guidelines” have been put together by various expert panels. This has condensed into the two predominant recommended guidelines presented here: for stroke and embolic protection is the CHA2DS2VASc score, and for the risk of bleeding is the HAS-BLED score. Let me review them for you:
CHADS2VASc (Stroke and Embolic Protection)
C CHF/ LV dysfunction (weak heart) Points: 1
H Hypertension (high blood pressure) 1
A Age > 75 (and up) 2
D Diabetes 1
S2 Stroke/ TIA 2
V Vascular Disease 1
A Age (between 65 to 74) 1
S Sex category (female has a higher risk) 1
Maximum Score 9
Risk Percentage
0 points <1%
1 1.3%
2 2.2%
3 3.2%
4 4.0%
5 6.7%
6 9.0%
7 9.6%
8 10.7%
9 15.2%
Despite earlier itineration such as CHADS, and CHADS2, this classification has shown to be more sensitive and specific.
In a study published in 2013, looking at Stroke and Systemic Embolism (SSE) rate in 11,414 patient-years, {all of whom were on Aspirin +/- Clopidogrel}, the incidence of SSE was 0.9% in patients with a CHA2DS2-VASc score of 1, and 2.1% with those with a score equal or greater than 2.
This has pretty much become the tipping point: a score of 2 or greater is when oral anti-coagulant drugs would be recommended.
In this study as well as the Swedish National Patient Registry of 140,000, [unexposed to anti-coagulant therapy], the incidence of stroke was 0.5% to 0.9% in the score of 1 , and in the score of 2 it was between 2 to 3%. In the 0 score range it was close to 0%. Therefore, the 2 or greater score groups are recommended to proceed with anti-coagulants, and the 0 score group are not recommended to proceed. It is the score of 1 where there is a debate. The tipping point for therapy in several scholarly editorials appears to be at about 1.7% for consideration of warfarin, and about 0.9% for consideration of the New Anti-Coagulant Therapies (NOACs). It is felt that the benefit of treatment may outweigh the risks at these percentages.
This sounds confusing so the American College of Cardiology, the AHA, and the Heart Rhythm Society have come up with these guidelines:
*CHA2DS2-VASc score is recommended for assessment of stroke risk in nonvalvular AF.
*With prior stroke, TIA, or CHA2DS2-VASC equal/greater than 2, Oral Anti-Coagulation is recommended with either warfarin or NOAC.
*Evaluate kidney function before initiation of NOAC.
*With a CHA2DS2-VASc score of 0, it is reasonable to omit Oral Anti-Coagulant Therapy.
*With a CHA2DS2-VASc score of 1, there is the choice of no anti-coagulant therapy, or treatment with anti-coagulant therapy, or treatment with aspirin.
What is interesting, is that in the large Swedish study mentioned above, over 40% of patients with a score of 1 were treated with Oral Anti-Coagulation, which was a higher percentage of those treated than in the higher score groups.
WHY?
I expect because the doctors were weighing the risks in the higher score groups against the further increased risk of bleeding, and the higher score groups have more illness and tend to be older thus making the risk of bleeding greater.
For example, people with history of GI bleeding, or intracranial bleeding, or elderly people who may be at greater risk for falling and injury, as well as those with cognitive impairment…all of these situations may preclude against giving someone an anti-coagulant.
So, what about bleeding?
There is a guideline published in 2013, called the HAS-BLED Score:
H Hypertension Score 1
A Abnormal kidney/liver function (1 point each) 1 or 2
S Stroke history 1
B Bleeding history 1
L Labile INR (difficult to control warfarin levels) 1
E Elderly (age >65 {sorry!}] 1
D Drugs or alcohol (aspirin, NSAIDS) 1
Just like the CHA2DS2-VASC score of accumulated scoring increases the incidence of stroke/embolus, accumulation of points in the HAS-BLED guidelines increase the risk of bleeding. For example, a score of 1 is associated with a 1.13% bleed rate, a score of 3 is associated with a 3.74% rate, and a score of 5 is associated with a 12.5% rate, etc.
The guidelines are very clear as to the purpose of evaluating bleed risk. It does not specifically state that Anti-Coagulation Therapy should not be used. What the guidelines say are:
1.The HAS-BLED score should be considered as a calculation to assess bleeding risk and if the score is equal or greater than 3, (high risk), some caution and regular review is needed following the initiation of anti-coagulant therapy, or anti platelet therapy.
2. Correctable risk factors for bleeding, such as uncontrolled blood pressure, labile INR’s, the use of other drugs, alcohol, should be addressed.
3. Use of the HAS-BLED score should be used to identify modifiable bleeding risks that need to be addressed, but should not be used on its own to exclude patients from Oral Anti-Coagulant Therapies.
The purpose of presenting all of this information to you was not to confuse you or overwhelm you, but to give you some education, and more importantly, how difficult it is to come to conclusions about scientific medical data that is not black and white.
We see one patient at a time, and though guidelines that are based on extensive clinical research data are there to “guide” us, the decision making process of how we come to recommend certain medications, therapies, surgeries, etc. is very much an individual thing, and hopefully you have doctors who try to do “right” for you.
(The current NOACs {New Oral Anti-Coagulants} are:
- Pradaxa, (dabigatran) 75 or 150 mg, twice daily
- Eliquis, (apixaban) 2.5 or 5 mg, twice daily
- Xarelto, (rivaroxaban) 15 or 20 mg, once daily
- Savaysa, (edoxaban) 30 or 60 mg, once daily)
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