Difference Between Valvular and Non-Valvular Atrial Fibrillation: Implications for Anticoagulation
Valvular AF refers specifically to AF in the setting of moderate to severe mitral stenosis or mechanical heart valves, while non-valvular AF encompasses all other forms of AF. This distinction is crucial as it determines anticoagulation strategy: warfarin is mandatory for valvular AF, while direct oral anticoagulants (DOACs) are preferred for non-valvular AF. 1
Definition and Classification
- Valvular AF is defined as AF occurring in the presence of moderate to severe mitral stenosis or mechanical heart valves 1
- Non-valvular AF includes AF in patients with other types of valvular disease such as:
- Bioprosthetic valves
- Mild mitral stenosis
- Native aortic, pulmonary, or tricuspid valve disease 1
- AF in the setting of mitral stenosis increases stroke risk 20 times over that of patients in sinus rhythm, while non-valvular AF increases stroke risk 5 times 1
Anticoagulation in Valvular AF
- For patients with AF and mechanical heart valves, warfarin is the only recommended anticoagulant 1
- Target INR for mechanical valves depends on valve type and position:
- The direct thrombin inhibitor dabigatran is specifically contraindicated in patients with AF and mechanical heart valves (Class III: Harm) 1
- Bridging therapy with unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) is recommended for patients with AF and mechanical heart valves undergoing procedures requiring warfarin interruption 1
Anticoagulation in Non-Valvular AF
- For patients with non-valvular AF, stroke risk is assessed using the CHA₂DS₂-VASc score 1
- Anticoagulation options for non-valvular AF include:
- DOACs are recommended over warfarin for non-valvular AF due to:
- For patients with non-valvular AF unable to maintain therapeutic INR with warfarin, switching to a DOAC is recommended 1
Special Considerations
- For patients with bioprosthetic valves, warfarin therapy with a target INR of 2.5 (range 2.0-3.0) is recommended for valves in the mitral position and suggested for valves in the aortic position for the first 3 months after valve insertion 3
- In patients with non-valvular AF and end-stage chronic kidney disease (CrCl <15 mL/min) or on hemodialysis, warfarin is preferred over DOACs 1
- DOACs (dabigatran and rivaroxaban) are not recommended in patients with AF and end-stage CKD or on dialysis due to lack of evidence 1
Clinical Implications and Monitoring
- For patients treated with warfarin, INR should be monitored at least weekly during initiation and at least monthly when stable 1
- Maximum protection against ischemic stroke in AF is achieved with an INR range of 2.0-3.0 1
- The risk of bleeding increases exponentially with INR values above 5.0 2
- Periodic reevaluation of anticoagulation therapy is recommended to reassess stroke and bleeding risks 1
Common Pitfalls to Avoid
- Misclassifying valvular status in AF patients, leading to inappropriate anticoagulant selection 1
- Using DOACs in patients with mechanical heart valves, which can lead to increased thromboembolic events 1
- Inadequate INR monitoring in patients on warfarin, which can lead to subtherapeutic or supratherapeutic levels 1
- Discontinuing anticoagulation without bridging therapy in high-risk patients undergoing procedures 1
- Using aspirin alone for stroke prevention in AF, which is significantly less effective than oral anticoagulation 4
Understanding the distinction between valvular and non-valvular AF is essential for selecting the appropriate anticoagulation strategy to effectively prevent thromboembolic events while minimizing bleeding risk.