A 58-year-old man with a history of rheumatic fever presents with progressive dyspnea on exertion and orthopnea. On examination, a loud S1 and an opening snap are heard at the apex. Chest X-ray shows straightening of the left heart border and pulmonary congestion. Which investigation is most appropriate to confirm the diagnosis and assess severity?

Explanation

## Diagnosis: Mitral Stenosis The clinical presentation—loud S1, opening snap, orthopnea, and CXR findings of straightening of the left heart border—is classic for **mitral stenosis (MS)**. ### Why Transthoracic Echocardiography with Doppler? **Key Point:** Transthoracic echocardiography (TTE) with Doppler is the **gold standard investigation** for diagnosing and grading mitral stenosis. **High-Yield:** Echocardiography provides: - Direct visualization of the mitral valve leaflets and commissural fusion - Measurement of mitral valve area (MVA) — critical for severity grading - Planimetry of the valve orifice in diastole - Continuous-wave Doppler to measure transmitral gradient and calculate MVA using the pressure half-time method - Assessment of left atrial size, left ventricular function, and pulmonary artery pressure - Detection of associated lesions (aortic stenosis, tricuspid regurgitation) **Clinical Pearl:** The **opening snap** heard on auscultation is caused by abrupt cessation of mitral leaflet opening; its presence confirms MS and its timing (earlier = more severe stenosis) correlates with MVA. ### Severity Grading by MVA | Severity | Mitral Valve Area (cm²) | Mean Gradient (mmHg) | Transmitral Flow Velocity (m/s) | |----------|-------------------------|----------------------|----------------------------------| | Mild | > 1.5 | < 5 | < 1.0 | | Moderate | 1.0–1.5 | 5–10 | 1.0–1.5 | | Severe | < 1.0 | > 10 | > 1.5 | **Tip:** TTE is non-invasive, widely available, reproducible, and requires no radiation—making it ideal for initial diagnosis and follow-up.