What is valvular atrial fibrillation (AF)?

Valvular Atrial Fibrillation: Definition and Clinical Implications

Valvular atrial fibrillation (AF) specifically refers to AF in patients with moderate to severe mitral stenosis (usually of rheumatic origin) or mechanical heart valves. This definition has evolved over time and has important implications for anticoagulation therapy selection.

Modern Definition of Valvular AF

The traditional distinction between "valvular" and "non-valvular" AF has been problematic and is now considered outdated. Current guidelines recommend a more functional approach:

• EHRA Type 1 VHD: AF patients with valvular heart disease requiring therapy with a Vitamin K antagonist (VKA) only

  • Moderate to severe mitral stenosis (usually rheumatic)
  • Mechanical prosthetic heart valves 1

• EHRA Type 2 VHD: AF patients with valvular heart disease who can be treated with either VKA or NOACs (Non-vitamin K Oral Anticoagulants)

  • Other native valvular diseases (mitral regurgitation, aortic stenosis, aortic regurgitation)
  • Bioprosthetic valves
  • Mitral valve repair 1

Why This Definition Matters

The distinction is primarily important for determining appropriate anticoagulation therapy:

1. Anticoagulation requirements: Patients with EHRA Type 1 VHD (mechanical valves, moderate-severe mitral stenosis) must use VKAs (warfarin) and cannot use NOACs 1

2. Clinical trials context: All major NOAC trials excluded patients with moderate-severe mitral stenosis and mechanical heart valves, but included patients with other types of valvular disease 1

3. Thromboembolism risk: The pathogenesis of thrombosis differs in mechanical valves compared to other forms of AF, explaining why NOACs performed poorly in the only trial with mechanical valves 2

Evolution of Terminology

The 2023 ACC/AHA/ACCP/HRS guideline explicitly states: "Valvular and nonvalvular terminology should be abandoned" 1. This is because:

• The terms created confusion in clinical practice
• Many patients with significant valvular disease were included in "non-valvular AF" trials
• The distinction is only relevant for selecting anticoagulation therapy, not for defining AF etiology 1

Clinical Implications

1. Anticoagulation decisions:

   • EHRA Type 1 VHD: Only VKAs (warfarin) should be used
   • EHRA Type 2 VHD: Either VKAs or NOACs can be used based on other clinical factors 1

2. Risk stratification:

   • Patients with significant valvular disease and AF generally have higher risk profiles
   • They often have more comorbidities, worse left ventricular function, and larger left atrial volumes 3

3. Prognosis:

   • AF with significant valvular disease is associated with higher rates of heart failure hospitalization
   • Cardiac structure and function are more important determinants of outcomes than the type of AF classification 3

Common Pitfalls to Avoid

1. Using outdated terminology: Avoid using "valvular AF" and "non-valvular AF" as general terms; instead, specify the exact valve pathology

2. Misclassifying patients: Not all valvular heart disease requires VKA therapy; only moderate-severe mitral stenosis and mechanical valves mandate VKA use

3. Overlooking other risk factors: Remember that thromboembolism risk in AF patients with valvular disease is also influenced by traditional CHA₂DS₂-VASc risk factors 4

4. Assuming all valve disease increases stroke risk equally: Different valve lesions have different impacts on thromboembolism risk in AF patients

In summary, the term "valvular AF" should be used specifically to refer to AF in patients with moderate-severe mitral stenosis or mechanical heart valves, conditions that require VKA therapy and contraindicate NOACs. Other types of valvular heart disease in AF patients do not fall under this definition and may be eligible for NOAC therapy.