A 32-year-old woman from rural India presents with dyspnea on exertion and orthopnea. Echocardiography confirms mitral stenosis with a valve area of 1.2 cm². Regarding the pathophysiology and clinical features of mitral stenosis, all of the following are true EXCEPT:

Explanation

## Pathophysiology of Mitral Stenosis **Key Point:** Left ventricular hypertrophy is NOT a feature of mitral stenosis. The stenotic mitral valve prevents blood flow into the left ventricle, resulting in a small, underfilled LV with normal or reduced wall thickness — not hypertrophy. ### Why LV Hypertrophy Does NOT Occur In mitral stenosis: - The obstruction is at the mitral valve level, not in the LV outflow tract - The LV receives less blood volume (reduced preload) - There is no increase in LV wall stress or pressure gradient across the LV - The LV remains **small and underfilled** — a hallmark finding on echocardiography ### Correct Features of Mitral Stenosis | Feature | Pathophysiology | |---------|------------------| | **Atrial fibrillation** | Occurs in ~50% of symptomatic patients; caused by chronic LA enlargement and increased LA pressure | | **Opening snap timing** | Occurs EARLIER in severe MS (shorter A2–OS interval) because elevated LA pressure closes the valve more rapidly | | **Pulmonary edema** | Results from elevated pulmonary capillary wedge pressure (PCWP) transmitted backward from LA through pulmonary veins | | **Left atrial enlargement** | Prominent; LA dilates to accommodate increased volume at higher pressures | | **RV hypertrophy** | May develop secondary to chronic pulmonary hypertension | **High-Yield:** The **small, underfilled LV** in mitral stenosis is a key distinguishing feature from aortic stenosis (where LV hypertrophy is prominent). **Clinical Pearl:** On chest X-ray, you may see a **straightened left heart border** (due to LA enlargement) and **pulmonary edema**, but the cardiac silhouette is often not enlarged because the LV is small. [cite:Harrison 21e Ch 297] --- ## Why Each Distractor Is Correct - **Option 1 (Atrial fibrillation):** True. Chronic LA pressure elevation and LA enlargement predispose to AF in ~50% of symptomatic MS patients. - **Option 2 (Opening snap timing):** True. In severe MS, the elevated LA pressure causes the mitral leaflets to close more rapidly, moving the opening snap earlier (shorter A2–OS interval). - **Option 3 (Pulmonary edema mechanism):** True. The stenotic valve prevents LA emptying, raising LA pressure, which is transmitted backward to pulmonary veins and capillaries.