Colbert Perez MDa, Alejandro Perez-Verdia MDb
Correspondence to Colbert Perez MD. Email: Colbert.perez@ttuhsc.edu
SWRCCC 2014;2(6):52-55
doi: 10.12746/swrccc2014.0206.080
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Atrial fibrillation is the most common arrhythmia
in clinical practice and accounts for significant
health care costs. An estimated 2.2 million people in
the US have this arrhythmia, and the incidence increases
annually by 1.3% to 18%.1 One important
consideration for patients with atrial fibrillation is the
risk of thromboembolic events. However, treatment
for stroke prevention often presents difficult decisions
for both patients and physicians.
Anticoagulation in patients with atrial fibrillation
reduces the risk of thromboembolic events, but
each patient’s risk is different. The easiest and best
known risk calculator to evaluate a patient’s risk is the CHADS2 score which can predict the risk of stroke
for the following year (Table 1).2 This score quickly
replaced the Atrial Fibrillation Investigators criteria
and Stroke Prevention in Atrial Fibrillation Investigatorscriteria scores since it provides more accurate
predictions and is simple to calculate and remember.
The more recent CHA2DS2-VASc includes three additional
risk factors and doubles the risk for age (Table
2). This provides better risk stratification for patients
considered at low risk based on their CHADS2 score
(CHADS2<1), a group in which 0.84%-3.2% of the
patients have a thromboembolic event each year.3
The European Society of Cardiology guidelines now
recommend the use of CHA2DS2-VASc score system
instead of the CHADS2. As a result of using the
CHA2DS2-VASc and identifying a higher risk in same
patients, more patients will be treated for thromboembolic
prevention (Table 3).
| CHADS2 | Score |
|---|---|
| CHF | 1 |
| Hypertension | 1 |
| Age >75 | 1 |
| Diabetes | 1 |
| Stroke or TIA | 2 |
| CHA2DS2-VASc | Score |
|---|---|
| CHF | 1 |
| Hypertension | 1 |
| Age >75 | 1 |
| Diabetes | 1 |
| Stroke or TIA | 2 |
| Vascular Disease | 2 |
| Age 65-74 | 2 |
| Female | 2 |
| Score | Adjusted Yearly Stroke Rate |
|---|---|
0 |
6.2 % |
1 |
10.0 % |
2 |
17.9 % |
3 |
23.6 % |
4 |
29.0 % |
5 |
40.9 % |
6 |
50.5 % |
The initial step in this treatment decision requires a choice in medication. Aspirin has a relatively low risk of bleeding (5.58 events per 1000 patientyears), and current ACC/AHA guidelines recommend that patients in low risk categories be treated with antiplatelet aspirin therapy.4 As the patient’s risk of stroke increases, anticoagulation becomes more beneficial. However, the patient’s risk and benefit with anticoagulation must be weighed prior to making a final decision with the patient.The CHA2DS2-VASc can evaluate stroke risk, and the HAS-BLED calculator can evaluate the risk of major bleeding (Table 4). The risk of a major bleed in the HAS-BLED categories ranges from 1.13% to 12.50% per year (Table 5).5 A consideration relevant to major bleeds in patients on oral anticoagulants is falls. However, a prospective study of 515 patients with 60% at a high risk for falls showed no significant increased incidence of bleeding in this group, and only three patients developed nonfatal subdural hematomas. A modeling study has also demonstrated that a patient would have to fall 295 times per year to outweigh the benefit of stroke prevention in patients on anticoagulation for atrial fibrillation.6
| Letter | Clinical Characteristic | Points |
|---|---|---|
H |
Hypertention |
1 |
A |
Abnormal renal and liver function |
1 or 2 |
S |
Stroke |
1 |
B |
Bleeding |
1 |
R |
Labile INRs |
1 |
E |
Elderly (>65) |
1 |
D |
Drugs of Alcohol |
1or 2 |
| Points | Annual Adjusted bleeding rate |
|---|---|
0 |
1.13 % |
1 |
1.02 % |
2 |
1.88 % |
3 |
3.74 % |
4 |
8.70 % |
5 |
12.50 % |
The standard and only oral anticoagulant for
many years was warfarin, but recently newer medications
have emerged that add other options for the
management of atrial fibrillation. These newer medications
do not require strict blood work monitoring,
and there is little interaction with other medications
and diet. Dabigatran (Pradaxa, a direct thrombin inhibitor)
was the first approved. The RE-LY (Randomized
Evaluation of Long-term Anticoagulation Therapy)
study reported a stroke event rate of 1.11% with
150 mg dabigatran twice daily compared to 1.69%
with warfarin. This medication had a similar bleeding
risk of 3.11% compared to warfarin’s 3.66% and the
added benefit of not requiring blood work monitoring.7 This simple twice daily medication has increased
compliance and ultimately eliminated the problem of
supra-therapeutic and sub-therapeutic complications
often seen with warfarin therapy. However, dabigatran
was found to have an unexplained increased risk
of MI and is not suitable for patients with a decreased
kidney function due to renal excretion. In 2011 the
ROCKET AF (Rivaroxaban Once-daily oral Direct
Factor Xa Inhibition Compared with Vitamin K Antagonism
for Prevention of Stroke and Embolism Trial in
Atrial Fibrillation) trial compared rivaroxaban (Xarelto,
a direct factor Xa inhibitor) to warfarin and found no
inferiority.8 The added advantage of this medication
is once daily dosing. However, the INR in the study
patients was in the therapeutic range only 55% of the
time and was lower than most studies (60-65%) with favor rivaroxaban. In addition, post study analysis of
the trial found a negative intention to treat outcome.
The ARISTOTLE (Apixaban for Reduction in Stroke
and Other Thromboembolic Events in Atrial Fibrillation)
trial published in 2012 had decreased mortality
and reduced risk of bleeding in patients treated with
apixaban (Eliquis, a direct factor Xa inhibitor), including
patients older than 75, when compared to warfarin.9 This drug is predominantly metabolized by the
liver and requires little adjustment in patients with
moderate renal dysfunction. Medications on the horizon,
such as Edoxaban (also a direct Factor Xa inhibitor)
which is currently being reviewed for approval
by the FDA, will offer more options for anticoagulation
in the future.10
Atrial fibrillation is a very common disease
in the US, and treatment for stroke prevention has
undergone drastic changes. Simple risk calculators
have been developed to estimate the yearly risk of
stroke and bleeding on anticoagulation, but ultimately
any decision about anticoagulation is a patient-physician
choice. Many factors contribute to this decision,
including compliance and the risk of falls. However,
newer medications have reduced compliance
problems compared to the previously widely used
warfarin. Also, the risk of falls has been shown not to
significantly increase the risk of a major bleed. Ultimately,
the patient and physician must decide about
the treatment of atrial fibrillation, but newer risk calculators
and medications can help guide the decision
and inform the discussion.
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Received: 2/2/2014
Accepted: 4/6/2014
Reviewers:Scott Shurmur MD
Published electronically: 4/15/2014
Conflict of Interest Disclosures: None