A 72-year-old woman with a 10-year history of hypertension presents with progressive dyspnea, orthopnea, and lower limb edema for 3 months. On examination, blood pressure is 165/95 mmHg, heart rate 78 bpm regular, JVP elevated at 8 cm H₂O. Auscultation reveals a hyperdynamic apical impulse displaced 2 cm lateral to the midclavicular line, a soft S1, a prominent S3 gallop, and a holosystolic murmur at the apex radiating to the axilla. Chest X-ray shows cardiomegaly with pulmonary edema. Echocardiography demonstrates severe left ventricular dilatation (LVEDD 68 mm), severe systolic dysfunction (LVEF 25%), and severe mitral regurgitation (regurgitant volume 60 mL). The mitral leaflets are structurally normal. What is the most likely etiology of the mitral regurgitation?

Explanation

## Clinical Diagnosis: Functional Mitral Regurgitation (FMR) **Key Point:** This patient has **functional (secondary) mitral regurgitation** — the mitral leaflets are structurally normal, but MR occurs due to geometric distortion of the left ventricle and mitral annulus. ## Pathophysiology of Functional MR ```mermaid flowchart TD A[Left Ventricular Dysfunction]:::outcome --> B[LV Dilatation]:::outcome B --> C[Mitral Annular Dilatation]:::outcome C --> D[Papillary Muscle Displacement]:::outcome D --> E[Leaflet Coaptation Failure]:::outcome E --> F[Functional MR]:::outcome A --> G[Reduced Systolic Function]:::outcome G --> H[Increased LV Wall Stress]:::outcome H --> I[Progressive Annular Dilatation]:::outcome I --> F ``` ## Distinguishing Features of This Case | Feature | Functional MR | Rheumatic MR | Endocarditis | Papillary Muscle Rupture | |---------|---------------|--------------|--------------|-------------------------| | Leaflet morphology | Normal | Thickened, restricted | Vegetation visible | Flail leaflet | | LV size | Dilated | Normal or dilated | Variable | Normal or dilated | | LVEF | Reduced | Normal or reduced | Variable | Acutely reduced | | Annular dilatation | Marked | Mild | Mild | Mild | | Onset | Gradual | Gradual | Acute/subacute | Acute | | Associated findings | S3 gallop, signs of HF | Stenotic lesions | Fever, emboli | Acute MR, shock | **High-Yield:** The **normal mitral leaflet structure on echo** is the key finding that excludes organic valve disease (rheumatic, endocarditis, papillary muscle rupture). ## Etiology of Functional MR in This Patient **Clinical Pearl:** The patient has: - Long-standing hypertension (10 years) → LV hypertrophy → progressive systolic dysfunction - Severe LV dilatation (LVEDD 68 mm) and severe systolic dysfunction (LVEF 25%) - Markedly dilated mitral annulus (consequence of LV dilatation) - Structurally normal mitral leaflets - Holosystolic murmur (indicates MR throughout systole due to persistent annular dilatation) This clinical picture is **pathognomonic for functional MR** secondary to dilated cardiomyopathy from hypertensive heart disease. ## Mechanism of Functional MR 1. **Chronic hypertension** → LV hypertrophy and fibrosis 2. **Progressive systolic dysfunction** → LV dilatation 3. **Annular dilatation** → Mitral leaflets fail to coapt properly 4. **Papillary muscle displacement** → Increased tethering of leaflets 5. **Result:** Holosystolic MR despite normal leaflet anatomy **Key Point:** Functional MR is a consequence of LV dysfunction, not a primary valve disease. Treatment focuses on **reducing LV afterload and improving contractility** (ACE inhibitors, beta-blockers, aldosterone antagonists, CRT/ICD if indicated). [cite:Harrison 21e Ch 297; Braunwald's Heart Disease 12e Ch 65]