Which of the following is not seen in mitral stenosis?

**Core Concept**
Mitral stenosis is a valvular heart disease characterized by the narrowing of the mitral valve orifice, leading to an obstruction of blood flow from the left atrium to the left ventricle. This condition often results from rheumatic heart disease, which causes scarring and fibrosis of the valve leaflets.

**Why the Correct Answer is Right**
In mitral stenosis, the mitral valve leaflets are usually thickened and fibrotic, resulting in a reduction in valve area and an increase in pressure in the left atrium. This increase in pressure can lead to left atrial enlargement, atrial fibrillation, and pulmonary hypertension. The characteristic murmur of mitral stenosis is a low-pitched, rumbling diastolic murmur heard at the apex.

**Why Each Wrong Option is Incorrect**
* **Option A:** Mitral regurgitation is often seen in mitral stenosis due to the leaflets being unable to close properly, allowing blood to flow back into the left atrium.
* **Option B:** Left atrial enlargement is a common complication of mitral stenosis due to the increased pressure in the left atrium.
* **Option C:** Pulmonary hypertension can develop in mitral stenosis due to the increased pressure in the left atrium causing right ventricular strain.

**Clinical Pearl / High-Yield Fact**
A classic clinical finding in mitral stenosis is the presence of a low-pitched, rumbling diastolic murmur heard at the apex, often described as a "purring" sound.

**Correct Answer: D. Mitral Regurgitation.**