What is the diagnosis for a patient with severe left and right atrial enlargement, mild to moderate mitral valve regurgitation, and trivial tricuspid regurgitation?

Diagnosis: Chronic Mitral Regurgitation with Secondary Biatrial Enlargement

The most likely diagnosis is chronic mitral regurgitation (MR) causing severe left atrial enlargement, with secondary right atrial enlargement due to either functional tricuspid regurgitation from right ventricular remodeling or coexisting rheumatic heart disease affecting both atrioventricular valves. 1

Primary Pathophysiologic Mechanism

The severe bilateral atrial enlargement in the context of mild-to-moderate MR and only trivial tricuspid regurgitation (TR) suggests a chronic, longstanding process rather than acute valvular dysfunction. 1

• Left atrial enlargement is an "additional essential criterion" for assessing MR severity and indicates chronic volume overload from the regurgitant lesion, even when the MR is graded as only mild-to-moderate by standard Doppler parameters. 1

• The discordance between "mild-to-moderate" MR and severe left atrial enlargement warrants subspecialty cardiology evaluation, as this descriptor itself signals diagnostic uncertainty that can result from technical limitations of echocardiography, including color Doppler overestimation or underestimation. 2

Mechanism of Right Atrial Enlargement

The severe right atrial enlargement with only trivial TR requires consideration of three mechanisms:

• Functional TR with spontaneous improvement: Right atrial and tricuspid annular dilation can persist even after functional TR improves, particularly if the patient previously had more significant TR that has since decreased in severity. 3, 4

• Rheumatic heart disease: Rheumatic MR is frequently associated with tricuspid valve involvement (38% have at least moderate TR, 4% have tricuspid stenosis), and combined left and right atrial enlargement is characteristic of rheumatic disease affecting both atrioventricular valves. 5, 6

• Chronic atrial fibrillation: The presence of preoperative atrial fibrillation is an independent determinant for development of severe isolated TR and can cause progressive atrial enlargement independent of valvular regurgitation severity. 4

Critical Diagnostic Considerations

The cardiologist must establish definitive MR grading using comprehensive echocardiographic parameters beyond color Doppler jet area alone, including vena contracta width (≥0.70 cm for severe), regurgitant volume (≥60 mL/beat for severe), regurgitant fraction (≥50% for severe), and regurgitant orifice area (≥0.40 cm² for severe). 1, 2

• Normal left ventricular size and function with severe left atrial enlargement suggests the MR may actually be more severe than the "mild-to-moderate" grading indicates, particularly if the regurgitation is eccentric and underestimated by standard color Doppler techniques. 7, 2

• Transesophageal echocardiography (TEE) or cardiovascular magnetic resonance (CMR) should be considered when uncertainty exists regarding MR severity, particularly for "mild to moderate" descriptors. 2

Etiology Assessment Required

The cardiologist must determine whether this represents:

• Primary (organic) MR: Degenerative disease with mitral valve prolapse, rheumatic disease with leaflet thickening/restriction, or endocarditis with leaflet destruction. 2, 5

• Secondary (functional) MR: Left ventricular dysfunction with annular dilation and leaflet tethering, though this is less likely given the reported normal echocardiogram findings aside from atrial enlargement. 2

Prognostic Implications

Combined left and right atrial enlargement carries significant prognostic implications:

• In surgical series, combined left and right atrial enlargement (versus isolated left atrial enlargement) was associated with higher operative mortality (20% vs 7%, p<0.05) in patients undergoing mitral valve replacement. 6

• Moderate or severe TR and right heart enlargement are independently associated with increased mortality even in other valve disease contexts, though the current patient has only trivial TR. 8

Common Diagnostic Pitfalls

• Overreliance on color Doppler jet area: A small central jet (<4 cm² or <20% LA area) is consistent with mild MR, but severe left atrial enlargement suggests chronic hemodynamic significance that may not be captured by jet area alone. 1

• Failing to recognize rheumatic disease: Pure mitral stenosis is uncommon (only 22% of MS patients have pure stenosis without MR), and rheumatic disease frequently involves multiple valves with characteristic biatrial enlargement. 5

• Assuming trivial TR excludes right heart disease: Tricuspid annular diameter and right atrial area can remain enlarged even after TR severity decreases, and isolated severe TR can develop years after initial valve surgery. 3, 4

Recommended Diagnostic Algorithm

1. Obtain detailed history: Prior rheumatic fever, history of atrial fibrillation, prior cardiac surgery, symptoms of heart failure (dyspnea, orthopnea, edema, abdominal bloating). 1, 4

2. Comprehensive echocardiographic reassessment: Measure vena contracta width, calculate regurgitant volume and fraction using PISA method, assess pulmonary vein flow patterns (systolic blunting suggests significant MR), measure tricuspid annular diameter (>40 mm or >21 mm/m² indicates significant dilation), and evaluate for rheumatic features (leaflet thickening, commissural fusion, restricted motion). 1, 2

3. Consider TEE if transthoracic imaging inadequate: Particularly for eccentric jets that may be underestimated by transthoracic echocardiography. 2

4. Assess for atrial fibrillation: ECG or ambulatory monitoring, as chronic AF is an independent risk factor for progressive atrial enlargement and TR. 4

5. Stage the disease: Use ACC/AHA four-stage classification (A through D) to guide surveillance timing and intervention decisions. 2