A Practical Guide to Anticoagulant Selection in Afib Patients: Part 1

Patients with non-valvular atrial fibrillation (NVAF) have an increased risk for stroke and death that is significantly reduced with adequate oral anticoagulation therapy.

The emergence of new oral anticoagulants (NOACs) presents pharmacists with an opportunity to intervene in assisting patients with selecting the most appropriate drug therapy. A recently published review on this topic highlighted several key points to consider when selecting the most appropriate agent based on patient specific characteristics.¹

Here is the first part of a summary I put together regarding optimized stroke prevention in patients with NVAF.

• Up to 30% of NVAF patients from 4 pivotal randomized trials of NOACs have concurrent coronary artery disease (CAD). Combined use of oral anticoagulation and antiplatelet medications significantly increased the risk of major bleeding. NOAC monotherapy is preferable for patients with NVAF and stable CAD. In select patient populations (eg, those with recent myocardial infarction or coronary artery stenting), the addition of aspirin is still indicated based on individual risk assessment of bleeding and the coronary anatomy. In patients undergoing percutaneous coronary intervention who require “triple therapy” with an oral anticoagulant, aspirin, and a second antiplatelet, a well-controlled vitamin K antagonist (VKA) [target therapeutic range (TTR) >70%, international normalized ratio (INR) range 2.0-2.5] or NOAC may be selected. If a NOAC is chosen, consideration can be given to lower dose when combining with dual antiplatelet therapy (eg, rivaroxaban 15 mg daily). However, this strategy has not been formally studied.
• Cardioversion is associated with a 5% to 7% risk of clinical thromboembolic events within 1 month in NVAF patients without a sufficient oral anticoagulant. Silent brain lesions are common after NVAF ablation procedures (10% to 15% of patients), but their clinical relevance and implications are uncertain. VKAs remain the standard of care for NVAF patients undergoing cardioversion. NOACs are safe and effective with particular advantages (eg, shortening the time to cardioversion), but ongoing trials will provide additional evidence on safety and efficacy. Warfarin remains the standard oral anticoagulant of choice for patients undergoing NVAF ablation procedures. Uninterrupted dabigatran, apixaban, or rivaroxaban are reasonable alternatives.
• Patients with mechanical valve prostheses or moderate-severe rheumatic mitral stenosis are not good candidates for NOAC therapy and should instead be treated with VKAs. Patients with other valvular abnormalities (eg, mitral, aortic, and tricuspid insufficiency and aortic stenosis) may be safely treated with a NOAC (especially apixaban or rivaroxaban) or VKA.
• Patients with high-quality VKA therapy (TTR >70%) have a low risk of thromboembolism and bleeding. It is reasonable to continue warfarin therapy for patients who have a TTR >70%. Changing from warfarin to a NOAC may be considered for patients with prior complications or a higher SAMe-TT₂R₂ score (Table), or based on individual patient preferences.²

Table: Calculation of SAMe-TT₂R₂ Score

Sex (female)

1 Point

Age (>60 years)

1 Point

Medical history*

1 Point

Treatment (rhythm control strategy)

1 Point

Tobacco use (within 2 years)

2 Points

Race (non-Caucasian)

2 Points

Maximum score

8 Points

*Medical history= 2 or more of the following conditions: hypertension, diabetes, coronary artery disease/myocardial infarction, peripheral arterial disease, congestive heart failure, previous stroke, pulmonary disease, hepatic or renal disease.

A total score of 0-2 points suggests that a patient may be able to achieve high-quality anticoagulation with warfarin-based therapy.

• Patients with NVAF and a single stroke risk factor (CHA₂DS₂-VASC score of 1 in males and 2 in females) are at modestly elevated risk for stroke. In patients with a single stroke risk factor other than gender, an oral anticoagulant should be considered based on limited clinical trial data of dabigatran or apixaban.
• Even when it is paroxysmal, NVAF is usually progressive. Therefore, patients with a first-documented episode of NVAF should be considered at sufficient risk of stroke to warrant consideration for an oral anticoagulant. The pattern of NVAF, frequency of NVAF episodes, or number of NVAF episodes should not influence oral anticoagulant selection.
• Commonly used antiarrhythmic medications frequently have interactions with VKA activity and metabolism, but rarely interact with NOACs. The dose of dabigatran or edoxaban (but not rivaroxaban or apixaban) should be reduced in patients taking verapamil. Dabigatran is contraindicated in combination with dronedarone. Edoxaban should be used at the 30 mg dose in patients taking dronedarone. Amiodarone use is generally safe to administer with all of the available NOAC agents.

References

1. Diener HC, et al. Choosing a particular oral anticoagulant and dose for stroke prevention in individual patients with non-valvular atrial fibrillation: part 1. Eur Heart J. 2016 Feb 4;pii:ehv643. [Epub ahead of print]

2. Fauchier L, et al. The SAMe-TT2R2 score and quality of anticoagulation in atrial fibrillation: a simple aid to decision-making on who is suitable (or not) for vitamin K antagonists. Europace. 2015;17:671-673.