What is the difference between valvular atrial fibrillation (AFib) and non-valvular atrial fibrillation?

Valvular vs. Non-Valvular Atrial Fibrillation: Differences and Implications

Valvular atrial fibrillation refers specifically to AF in the setting of moderate-to-severe mitral stenosis or mechanical heart valves, while non-valvular AF refers to AF in the absence of these specific conditions, even if other valve diseases are present. 1, 2

Definitions and Classification

• Valvular AF is defined as AF occurring in patients with moderate to severe mitral stenosis or mechanical heart valves 1
• Non-valvular AF does not imply the absence of all valvular heart disease, but rather specifically excludes only moderate-to-severe mitral stenosis and mechanical heart valves 1
• The distinction is clinically important because it determines anticoagulation strategy and medication options 2

Stroke Risk Differences

• Valvular AF in the setting of mitral stenosis increases stroke risk 20-fold compared to patients in sinus rhythm 1, 2
• Non-valvular AF increases stroke risk approximately 5-fold 1, 2
• Patients with valvular AF generally have higher thromboembolic risk than those with non-valvular AF 1

Anticoagulation Strategies

For Valvular AF:

• Warfarin is the only recommended anticoagulant for patients with mechanical heart valves or moderate-to-severe mitral stenosis 1, 2
• Target INR is typically 2.0-3.0 for most patients with valvular AF, but may be higher (2.5-3.5) for mechanical mitral valves 1
• Direct oral anticoagulants (DOACs) are contraindicated in patients with mechanical heart valves 1, 2, 3
• Dabigatran specifically has a Class III: Harm recommendation in patients with mechanical heart valves 2

For Non-Valvular AF:

• Anticoagulation options include both warfarin and DOACs (dabigatran, rivaroxaban, apixaban, and edoxaban) 1
• DOACs are generally preferred over warfarin for non-valvular AF due to similar or better efficacy and lower risk of intracranial bleeding 1
• Stroke risk is assessed using the CHA₂DS₂-VASc score to determine need for anticoagulation 1
• Anticoagulation is recommended for men with a CHA₂DS₂-VASc score ≥2 or women with a score ≥3 1

Clinical Implications and Monitoring

• Patients with valvular AF require more frequent INR monitoring when on warfarin, typically weekly during initiation and monthly when stable 1
• The risk of thromboembolic events increases with accumulation of risk factors in both valvular and non-valvular AF 4
• Patients with non-valvular AF who are on warfarin have better outcomes when their INR is maintained within the therapeutic range of 2.0-3.0 5

Common Pitfalls to Avoid

• Misclassifying valvular status can lead to inappropriate anticoagulant selection 2
• Using DOACs in patients with mechanical heart valves can lead to increased thromboembolic events and is contraindicated 2, 3
• Stopping anticoagulation abruptly in patients with AF increases stroke risk significantly 3
• Inadequate INR control in patients with valvular AF on warfarin is associated with increased thromboembolic events 4

Special Considerations

• Patients with bioprosthetic valves, mild mitral stenosis, or other native valve diseases (aortic, pulmonary, tricuspid) are classified as having non-valvular AF and can receive DOACs 1, 6
• In clinical trials of DOACs, up to 20% of enrolled patients had various valvular defects (excluding moderate-to-severe mitral stenosis and mechanical valves) 1
• Patients with rheumatic mitral valve disease have traditionally been excluded from DOAC trials and should receive warfarin 1, 6

Understanding the distinction between valvular and non-valvular AF is crucial for selecting the appropriate anticoagulation strategy to reduce morbidity and mortality from thromboembolic events.