Can the CHADS(Vascular) VASc score be used in valvular atrial fibrillation?

CHA₂DS₂-VASc Score Should NOT Be Used in Valvular Atrial Fibrillation

The CHA₂DS₂-VASc score is specifically designed and validated only for non-valvular atrial fibrillation and should not be applied to patients with valvular AF, particularly those with mechanical heart valves or moderate-to-severe mitral stenosis. 1

Definition of Non-Valvular vs. Valvular AF

• The American College of Cardiology explicitly states that the CHA₂DS₂-VASc score is recommended for assessment of stroke risk in patients with non-valvular atrial fibrillation only 1
• Valvular AF traditionally refers to AF in the presence of mechanical heart valves or moderate-to-severe rheumatic mitral stenosis, which were exclusion criteria in all validation studies 1
• The distinction is critical because patients with mechanical heart valves require warfarin with specific INR targets (2.0-3.0 or 2.5-3.5) based on valve type and location, regardless of any risk score 1

Why CHA₂DS₂-VASc Cannot Be Used in Valvular AF

• Mechanical heart valves: The American College of Cardiology mandates warfarin therapy for all patients with mechanical heart valves, with INR targets determined by prosthesis type and location—not by any stroke risk score 1
• Direct oral anticoagulants (NOACs) are contraindicated with mechanical heart valves, as dabigatran showed increased thromboembolic and bleeding events in this population 1
• The CHA₂DS₂-VASc score was never validated in patients with mechanical valves, as these patients were systematically excluded from all major AF trials 1

Special Consideration for Bioprosthetic Valves

• Patients with bioprosthetic heart valves represent a gray zone, as they were not included in the original CHA₂DS₂-VASc validation studies 1
• Limited evidence from subgroup analyses in the ARISTOTLE and ENGAGE AF-TIMI 48 trials (41 and 191 patients respectively) suggests that NOACs may be reasonable alternatives to warfarin in patients with remote bioprosthetic valve implantation 1
• However, the American College of Cardiology states that further study is needed before routinely using the CHA₂DS₂-VASc score for long-term risk assessment in AF patients with bioprosthetic valves 1
• One brief report suggested that in AF patients with bioprosthetic valves, a low CHA₂DS₂-VASc score was associated with low thromboembolic risk regardless of valve presence, but this requires additional validation 1

Clinical Algorithm for Anticoagulation in Valvular AF

For mechanical heart valves:

• Prescribe warfarin immediately, regardless of any risk score 1
• Target INR 2.0-3.0 for bileaflet aortic valves in normal sinus rhythm 1
• Target INR 2.5-3.5 for mechanical mitral valves or older-generation mechanical aortic valves 1
• Add low-dose aspirin based on valve-specific guidelines 1

For moderate-to-severe rheumatic mitral stenosis:

• Prescribe warfarin with target INR 2.0-3.0 1
• Do not use CHA₂DS₂-VASc score for decision-making 1

For bioprosthetic valves with AF:

• Short-term anticoagulation (typically 3-6 months post-implantation) is standard practice 1
• For long-term management, consider using CHA₂DS₂-VASc score cautiously, recognizing limited validation in this population 1
• NOACs may be considered as alternatives to warfarin based on emerging but limited evidence 1

Common Pitfalls to Avoid

• Never apply CHA₂DS₂-VASc scoring to patients with mechanical heart valves—these patients require warfarin regardless of score 1
• Do not assume that "valvular AF" includes all patients with any valve disease; the term specifically refers to mechanical valves and moderate-to-severe mitral stenosis 1
• Avoid using NOACs in patients with mechanical heart valves, as this is associated with increased harm 1
• Do not withhold anticoagulation in patients with mechanical valves even if they have no other stroke risk factors 1