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

From the Guidelines

Valvular atrial fibrillation occurs when AF is associated with moderate to severe mitral stenosis or mechanical heart valves, while non-valvular atrial fibrillation refers to AF without these specific valvular conditions. This distinction is crucial for anticoagulation therapy decisions. The most recent and highest quality study, 1, provides guidance on the management of patients with atrial fibrillation, including the distinction between valvular and non-valvular AF. Patients with valvular AF require vitamin K antagonists (warfarin) with a target INR of 2.0-3.0 (or higher for mechanical valves), as direct oral anticoagulants (DOACs) are contraindicated in these cases. For non-valvular AF, DOACs such as apixaban (5mg twice daily), rivaroxaban (20mg daily), dabigatran (150mg twice daily), or edoxaban (60mg daily) are preferred over warfarin due to their comparable efficacy, lower bleeding risk, and no need for regular INR monitoring. Some key points to consider in the management of AF include:

• The risk of thromboembolism is higher in patients with mechanical prostheses in the mitral position compared to the aortic position
• The use of DOACs is recommended over warfarin for patients with non-valvular AF, except in cases where DOACs are contraindicated
• The selection of an anticoagulant agent should be based on shared decision-making, taking into account risk factors, cost, tolerability, patient preference, and other clinical characteristics. The pathophysiology of valvular and non-valvular AF also differs, with valvular AF often resulting from structural changes and hemodynamic stress caused by valve disease, while non-valvular AF typically stems from electrical abnormalities, fibrosis, or other cardiac conditions not directly related to valve pathology, as noted in 1. Dose adjustments may be needed based on age, weight, and kidney function, and the risk of bleeding should be carefully considered when selecting an anticoagulant, as discussed in 1 and 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). ... 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 (AFib) is the presence of valvular heart disease, such as mitral stenosis or prosthetic heart valves, in valvular AFib.

• Valvular AFib involves heart valves and may require different anticoagulation management, such as increased target INR and addition of aspirin.
• Non-valvular AFib does not involve valvular heart disease and has been studied in clinical trials, with recommended anticoagulation therapy with warfarin to reduce thromboembolic events, including stroke 2.

From the Research

Definition and Classification

• The term "valvular atrial fibrillation" refers to patients with mitral stenosis or artificial heart valves, and should be treated with Vitamin K antagonists (VKAs) 3.
• "Non-valvular atrial fibrillation" refers to patients without mitral stenosis or artificial heart valves, and may include other types of valvular heart disease 3.
• A proposed classification system, Evaluated Heartvalves, Rheumatic or Artificial (EHRA), categorizes valvular heart disease into two types: EHRA Type 1 VHD, which refers to AF patients with 'VHD needing therapy with a Vitamin K antagonist (VKA); and EHRA Type 2 VHD, which refers to AF patients with 'VHD needing therapy with a VKA or a Non-VKA oral anticoagulant (NOAC)' 4.

Risk of Thromboembolism

• Valvular heart diseases, such as mitral regurgitation, aortic stenosis, and aortic insufficiency, do not result in conditions of low flow in the left atrium, and do not apparently increase the risk of thromboembolism brought by AF 3.
• The CHA2DS2VASc score is a clinical risk stratification tool that estimates the risk of stroke and thromboembolism in non-valvular atrial fibrillation, and is also useful in patients with valvular heart disease 5, 6.
• Patients with valvular AF have a higher risk of thromboembolic events compared to those with non-valvular AF, and are more often prescribed antithrombotic therapy 5, 6.

Management and Treatment

• Antithrombotic therapy is underused in patients with atrial fibrillation, and there is a need for proper application of risk stratification schemes for stroke and appropriate use of antithrombotics to prevent thromboembolism 7.
• The management of patients with valvular and non-valvular atrial fibrillation should be based on the principles of evidence-based medicine, and should take into account the type of valvular heart disease, the risk of thromboembolism, and the need for antithrombotic therapy 4, 6.
• Patients with valvular AF are more frequently prescribed antithrombotic therapy than patients with non-valvular AF, and in-hospital mortality is relatively low in both valvular and non-valvular AF patients 6.