From the Guidelines
Atrial fibrillation (AF) should be classified as either valvular or non-valvular to determine the appropriate anticoagulation strategy, with valvular AF requiring warfarin and non-valvular AF preferring direct oral anticoagulants (DOACs) like apixaban, rivaroxaban, dabigatran, or edoxaban due to their reduced bleeding risk and fixed dosing. The distinction between valvular and non-valvular AF is crucial because valvular AF carries a higher stroke risk, and mechanical valves create additional thrombogenic surfaces requiring more intensive anticoagulation 1.
Key Considerations
- Valvular AF refers to AF associated with moderate to severe mitral stenosis or mechanical heart valves, and requires warfarin (target INR 2.5-3.5 for mechanical valves, 2.0-3.0 for mitral stenosis) as DOACs are contraindicated in these cases.
- Non-valvular AF encompasses all other forms of AF, including those with other valve diseases like mitral regurgitation, aortic stenosis, or bioprosthetic valves, and prefers DOACs like apixaban (5mg twice daily), rivaroxaban (20mg daily), dabigatran (150mg twice daily), or edoxaban (60mg daily) over warfarin due to their reduced bleeding risk and fixed dosing without need for regular monitoring.
- Dose adjustments may be needed based on age, weight, and renal function, and the selection of an anticoagulant agent should be based on shared decision-making that takes into account risk factors, cost, tolerability, patient preference, potential for drug interactions, and other clinical characteristics 1.
Recent Guidelines
The 2021 guideline for the prevention of stroke in patients with stroke and transient ischemic attack recommends that in patients with valvular heart disease except moderate to severe mitral stenosis or a mechanical heart valve, ischemic stroke or TIA, and AF, DOACs (apixaban, dabigatran, edoxaban, and rivaroxaban) are recommended over warfarin therapy 1.
Clinical Implications
When evaluating a patient with AF, determining the presence of significant mitral stenosis or mechanical heart valves is essential for selecting the appropriate anticoagulation strategy, and the use of DOACs may be preferred over warfarin in patients with non-valvular AF due to their reduced bleeding risk and fixed dosing 1.
From the FDA Drug Label
Atrial Fibrillation Five recent clinical trials evaluated the effects of warfarin in patients with non-valvular atrial fibrillation (AF). Meta-analysis findings of these studies revealed that the effects of warfarin in reducing thromboembolic events including stroke were similar at either moderately high INR (2.0-4.5) or low INR (1.4-3. 0). There was a significant reduction in minor bleeds at the low INR. There are no adequate and well-controlled studies in populations with atrial fibrillation and valvular heart disease. For patients with AF and mitral stenosis, anticoagulation with oral warfarin is recommended (7th ACCP) For patients with AF and prosthetic heart valves, anticoagulation with oral warfarin should be used; the target INR may be increased and aspirin added depending on valve type and position, and on patient factors.
The main difference between valvular and non-valvular atrial fibrillation is the presence of valvular heart disease.
- Non-valvular atrial fibrillation: The recommended INR range for warfarin therapy is 2.0-3.0.
- Valvular atrial fibrillation: There are no adequate and well-controlled studies, but anticoagulation with oral warfarin is recommended for patients with mitral stenosis or prosthetic heart valves, with a target INR that may be increased and aspirin added depending on valve type and position, and on patient factors 2.
From the Research
Valvular vs Non-Valvular Atrial Fibrillation
- Valvular atrial fibrillation refers to atrial fibrillation in the presence of valvular heart disease, which can increase the risk of stroke and thromboembolism 3, 4.
- Non-valvular atrial fibrillation, on the other hand, refers to atrial fibrillation in the absence of valvular heart disease.
- The management of valvular and non-valvular atrial fibrillation differs, with valvular atrial fibrillation often requiring more aggressive anticoagulation therapy 5, 6.
Anticoagulation Therapy
- Direct oral anticoagulants (DOACs) have been shown to be safe and effective in patients with valvular atrial fibrillation, with similar outcomes to warfarin 3, 5.
- However, the use of DOACs in patients with bioprosthetic valves or rheumatic mitral stenosis is still uncertain, and vitamin K antagonists may be preferred in these cases 4, 6.
- A network meta-analysis found that DOACs performed better than warfarin in reducing stroke, systemic embolism, and intracranial hemorrhage in patients with valvular heart disease, but rivaroxaban was associated with an increased risk of major bleeding 6.
Patient Outcomes
- Patients with valvular atrial fibrillation who are switched from warfarin to DOACs have been shown to have improved outcomes, including reduced risk of death and major bleeding 5, 7.
- However, patients with low warfarin time in therapeutic range (TTR) may be at increased risk of non-adherence to DOACs, highlighting the need for close monitoring and adherence-oriented interventions 7.
- Further research is needed to fully understand the risks and benefits of DOAC use in patients with valvular atrial fibrillation, particularly in those with bioprosthetic valves or rheumatic mitral stenosis 4, 6.