A 38-year-old woman presents with dyspnea on exertion and a pansystolic murmur best heard at the apex with radiation to the axilla. Clinical examination suggests mitral regurgitation. Which investigation is most appropriate to assess the severity and mechanism of the lesion?

Explanation

## Investigation of Choice for Mitral Regurgitation Assessment ### Why Transthoracic Echocardiography with Doppler is Correct **Key Point:** Transthoracic echocardiography with color Doppler is the gold standard, non-invasive investigation for assessing both the anatomical mechanism and hemodynamic severity of mitral regurgitation. **High-Yield:** Doppler echocardiography provides: - Visualization of leaflet morphology and motion - Quantification of regurgitant jet area and volume - Assessment of left atrial and left ventricular dimensions - Calculation of regurgitant fraction and effective regurgitant orifice (ERO) - Determination of etiology (functional vs. organic) ### Echocardiographic Parameters in Mitral Regurgitation | Parameter | Mild MR | Moderate MR | Severe MR | |-----------|---------|-------------|----------| | Regurgitant jet area (% LA) | <20% | 20–50% | >50% | | Regurgitant volume (mL/beat) | <30 | 30–60 | >60 | | Effective regurgitant orifice (mm²) | <20 | 20–40 | >40 | | Left ventricular end-diastolic diameter | Normal | Normal/↑ | ↑↑ | **Clinical Pearl:** The pansystolic (holosystolic) murmur with apical location and axillary radiation is pathognomonic for mitral regurgitation; echocardiography confirms the diagnosis and guides management (medical vs. surgical). ### Why This Question Tests Understanding The stem provides a classic clinical presentation of mitral regurgitation and asks for the *most appropriate* investigation to assess *severity and mechanism*. Echocardiography alone answers both parts; cardiac catheterization is invasive and reserved for hemodynamic assessment when non-invasive data are inconclusive or when coronary anatomy must be defined preoperatively. [cite:Harrison 21e Ch 297]