Does moderate functional Mitral Regurgitation (MR) and Tricuspid Regurgitation (TR) contribute to the development of atrial fibrillation in patients with underlying heart disease?

Does Moderate Functional MR and TR Contribute to Atrial Fibrillation?

Yes, moderate functional mitral regurgitation (MR) and tricuspid regurgitation (TR) both contribute to and result from atrial fibrillation, creating a bidirectional relationship where these valvular lesions and AF perpetuate each other through progressive atrial remodeling and annular dilatation. 1

The Bidirectional Relationship

AF as a Cause of Functional MR and TR

Atrial fibrillation directly causes functional MR and TR through a specific mechanism called "atrial secondary" regurgitation, which occurs via:

• Mitral annular dilatation from AF-induced left atrial enlargement, even when left ventricular function remains preserved 1
• Tricuspid annular dilatation and flattening with right atrial dilatation but without RV remodeling, representing the "atrial" subtype of secondary TR 1
• This mechanism is distinct from ventricular functional regurgitation and occurs specifically in patients with AF and preserved ejection fraction 2, 3

Valvular Regurgitation as a Contributor to AF Development and Persistence

Moderate or greater MR independently predicts AF development and persistence through several mechanisms:

• Left atrial enlargement from chronic volume overload creates the substrate for AF initiation and maintenance 1
• In patients with MR due to mitral valve prolapse, there is a high risk of developing atrial fibrillation 1
• Recent onset of atrial fibrillation in the setting of severe MR is considered an indication for surgery when valve repair likelihood is high, as AF presence indicates advanced atrial remodeling 1

Clinical Significance and Prognosis

The Combination is Particularly Ominous

When moderate or greater functional MR and TR coexist in AF patients, the prognosis is dramatically worse:

• Patients with both significant functional MR and TR had only a 21% event-free rate at 24 months follow-up 2
• This combination independently predicts cardiac death, heart failure admission, and need for valve surgery 2
• The combination of significant MR with secondary TR is associated with worse prognosis compared to single valve disease 1

Prevalence Data

• In AF patients with preserved LVEF, 8.1% have significant functional MR and 15% have significant TR 2
• Among patients with MR, 19% have at least moderate-grade TR 1
• Significant functional MR and TR are more frequently seen in patients with AF duration >10 years (28% vs 25%, respectively), indicating progressive disease 2

Mechanistic Understanding: The Vicious Cycle

The relationship creates a self-perpetuating cycle:

1. AF causes atrial remodeling → left and right atrial dilatation 1
2. Atrial dilatation causes annular dilatation → functional MR and TR develop 1, 2, 3
3. Volume overload from regurgitation → further atrial dilatation 3
4. Progressive atrial enlargement → AF becomes more persistent and difficult to treat 1

Additional Contributing Factors

• Posterior mitral leaflet hamstringing relates to AFMR generation in AF patients 3
• Cardiac implantable electronic devices (CIED) may contribute to TR severity in these patients 1

Critical Clinical Implications

Predictors of Persistent AF After Valve Surgery

The presence and duration of AF before intervention determines outcomes:

• AF duration >1 year and left atrial size >50 mm predict persistent AF after successful valve surgery 1
• AF duration ≥3 months predicts 80% persistent AF after mitral valve repair, while AF <3 months had 0% persistence 1
• Preoperative atrial fibrillation is an independent predictor of reduced long-term survival after mitral valve surgery for chronic MR 1

Risk Factors for Incident AFMR in AF Patients

Independent risk factors include:

• Age ≥65 years 4
• Female sex 4
• Increased left atrial volume index (LAVI) 4
• Diastolic dysfunction 4
• Rate control strategy (vs rhythm control) in AF patients 4

Management Considerations

When to Intervene

The European Association of Cardiovascular Imaging emphasizes that identification of TR and MR etiology has critical management implications:

• In some cases, surgical and transcatheter interventions should be considered only after optimal heart failure therapy (including cardiac resynchronization) or treatment of underlying rhythm abnormalities 1
• Resolution of MR by surgical or transcatheter intervention might lead to significant improvement of TR in selected cases 1

The Role of Rhythm Control

Rhythm control strategy is protective against incident AFMR compared to rate control 4, suggesting that:

• Aggressive rhythm control may prevent progression of functional regurgitation
• Early AF treatment may interrupt the vicious cycle before irreversible atrial remodeling occurs

Predictors of Lack of TR Improvement After Mitral Intervention

Key predictors include:

• Right atrial dilation 1
• TR severity 1
• Tricuspid annular dilation 1
• Presence of atrial fibrillation 1

These factors indicate advanced disease stage requiring tailored therapeutic strategies 1.

Common Pitfalls to Avoid

Assessment Challenges

In the presence of significant TR, MR severity could be underestimated due to decreased LV preload 1

TR severity can be dynamic in relation to changes in MR severity and pulmonary pressures, requiring serial assessments 1

The "Chicken or Egg" Dilemma

Do not assume causality direction without careful evaluation:

• Determine whether TR is "ventricular" (from long-standing primary MR with RV remodeling) or "atrial" (from AF-induced atrial dilatation without RV remodeling) 1
• This distinction fundamentally changes management approach

Timing of Intervention

The ACC/AHA guidelines note that many clinicians consider recent onset of atrial fibrillation an indication for surgery in itself when there is high likelihood of valve repair 1, because:

• Short AF duration (<3 months) allows for AF resolution after valve repair
• Longer AF duration leads to irreversible atrial remodeling