A 58-year-old man from rural India presents with progressive dyspnea on exertion for 6 months and orthopnea. He has a history of acute rheumatic fever (ARF) at age 12. On examination, blood pressure is 140/90 mmHg, pulse is 88/min and regular. Auscultation reveals a loud S1, an opening snap at 0.08 s after A2, and a low-pitched diastolic murmur best heard at the apex with the patient in the left lateral decubitus position. Chest X-ray shows pulmonary edema and straightening of the left heart border. Echocardiography demonstrates a mitral valve area of 1.2 cm² with preserved left ventricular ejection fraction. What is the most likely diagnosis?

Explanation

## Diagnosis: Mitral Stenosis with Normal Sinus Rhythm ### Clinical Presentation The patient presents with the classic triad of mitral stenosis (MS): 1. **Progressive dyspnea and orthopnea** — due to pulmonary venous congestion from elevated left atrial pressure 2. **History of acute rheumatic fever** — the most common etiology of MS in India 3. **Preserved LVEF** — MS does not cause primary LV dysfunction; the obstruction is at the valve level ### Auscultatory Findings **Key Point:** The **loud S1** and **opening snap (OS)** are pathognomonic for mitral stenosis. - **Loud S1**: Occurs because the mitral leaflets remain mobile and are still in the open position at the moment of ventricular contraction, creating a forceful closure sound. - **Opening snap (OS)**: Occurs 0.08 s after A2 (aortic valve closure). The shorter the A2–OS interval, the more severe the stenosis (higher LA pressure forces the valve open earlier). - **Diastolic murmur**: Low-pitched, rumbling, best heard at the apex with the patient in the left lateral decubitus position. This is the hallmark of MS. ### Echocardiographic Findings - **Mitral valve area (MVA) = 1.2 cm²** — diagnostic of moderate-to-severe MS (normal >4 cm²; mild 2.5–4 cm²; moderate 1.5–2.5 cm²; severe <1.5 cm²) - **Preserved LVEF** — rules out primary LV dysfunction ### Why Normal Sinus Rhythm (Not Atrial Fibrillation)? **High-Yield:** The pulse is described as **regular** at 88/min. Atrial fibrillation would produce an **irregular** pulse. Although AF is common in MS (especially severe MS with large LA), the regular rhythm here excludes it. ### Pathophysiology ```mermaid flowchart TD A[Rheumatic Mitral Valve Damage]:::outcome --> B[Commissural Fusion & Leaflet Thickening] B --> C[Increased Valve Resistance] C --> D[↑ Left Atrial Pressure]:::outcome D --> E[Pulmonary Venous Congestion]:::outcome E --> F[Dyspnea & Orthopnea]:::outcome D --> G[Left Atrial Enlargement] G --> H{Severe Enlargement?}:::decision H -->|Yes| I[Atrial Fibrillation]:::outcome H -->|No| J[Normal Sinus Rhythm]:::outcome ``` ### Chest X-ray Findings - **Pulmonary edema**: Reflects elevated LA pressure transmitted back to pulmonary veins - **Straightening of left heart border** (loss of the normal concavity): Due to left atrial enlargement pushing the left main bronchus posteriorly **Clinical Pearl:** The combination of loud S1, OS, and diastolic murmur in a patient with a history of ARF and pulmonary edema is virtually diagnostic of mitral stenosis. **Mnemonic: LOUD S1 in MS** — **L**eaflets **O**pen **U**nexpectedly **D**uring **S**ystole (because the valve is still mobile and the LA pressure is high).