What type of heart failure is most commonly associated with mild‑to‑moderate mitral regurgitation?

Mild-to-Moderate Mitral Regurgitation and Heart Failure Type

Mild-to-moderate mitral regurgitation is most commonly associated with heart failure with preserved ejection fraction (HFpEF), where it reflects left atrial myopathy and annular dilatation rather than primary valve disease. 1

Understanding the Relationship

Secondary (functional) mitral regurgitation is the predominant pattern seen with mild-to-moderate MR in the heart failure population:

• In HFpEF patients, mild-to-moderate functional MR occurs in a substantial proportion and reflects underlying left atrial dysfunction and myopathy, even in the absence of atrial fibrillation 1
• The mitral valve leaflets themselves are structurally normal; the regurgitation results from left atrial and annular dilatation, not intrinsic valve pathology 2
• Mitral annular dilatation correlates strongly with left atrial dilatation (r=0.63) but only weakly with left ventricular remodeling (r=0.37), indicating that atrial pathology drives the regurgitation 1

Hemodynamic Patterns by Heart Failure Type

HFpEF with mild-to-moderate MR demonstrates specific characteristics:

• Patients display greater left atrial volume, reduced left atrial strain and compliance, and more adverse pulmonary hemodynamics compared to HFpEF patients without MR 1
• Even mild secondary MR is associated with a twofold increase in mortality in heart failure patients 2
• The regurgitation reflects chronic pressure and volume overload on the left atrium rather than primary valve dysfunction 3

HFrEF (heart failure with reduced ejection fraction) can also present with secondary MR:

• Secondary MR occurs in approximately 24% of patients with chronic systolic heart failure of any etiology 2
• The mechanism involves left ventricular dilatation causing leaflet tethering and malcoaptation 2
• Left ventricular systolic and diastolic dysfunction, along with atrial fibrillation, contribute to left atrial and left ventricular dilation that drives the regurgitation 2

Critical Distinction: Primary vs. Secondary MR

Primary MR (degenerative valve disease) follows a different pattern:

• Primary MR imposes pure volume overload and would be expected to cause left ventricular and left atrial dilation with preserved or supranormal ejection fraction initially 2
• Chronic severe primary MR eventually leads to left ventricular systolic dysfunction and heart failure, but mild-to-moderate primary MR typically does not cause heart failure 4, 5
• When you see mild-to-moderate MR with heart failure symptoms, suspect secondary MR from underlying cardiomyopathy rather than primary valve disease 2

Practical Clinical Algorithm

When evaluating mild-to-moderate MR with heart failure:

1. Assess valve morphology carefully - normal leaflets indicate secondary MR; abnormal leaflets (prolapse, flail, thickening) suggest primary MR 2

2. Evaluate left ventricular function:

   • Preserved LVEF (≥50%) with dilated left atrium → likely HFpEF with secondary atrial functional MR 1
   • Reduced LVEF (<40%) with LV dilation → likely HFrEF with secondary ventricular functional MR 2

3. Assess left atrial size and function:

   • Significant left atrial enlargement with mild-to-moderate MR strongly suggests secondary MR from atrial myopathy 3, 1
   • Normal left atrial size with mild-to-moderate MR makes severe hemodynamic consequences unlikely 2

Common Pitfalls to Avoid

Do not assume mild-to-moderate MR is hemodynamically insignificant:

• Even mild secondary MR independently predicts worse outcomes in heart failure patients 2
• Patients with MR-HFpEF display worse biventricular function, more adverse pulmonary hemodynamics, and reduced exercise capacity compared to HFpEF without MR 1

Do not misinterpret anterior leaflet override as primary MR:

• In secondary MR, the anterior leaflet may appear to override the posterior leaflet at end-systole, mimicking prolapse 2
• However, neither leaflet moves above the annular plane into the left atrium; both are tethered into the ventricle throughout systole 2

Recognize that stiff left atrium can have elevated pressures even with mild MR:

• Post-ablation or infiltrative cardiomyopathy can cause elevated left atrial pressures despite only mild regurgitation 2
• Elevated left atrial V waves have been reported in heart failure with preserved LVEF even without significant MR 2