In mitral stenosis, double atrial shadow is due to
**Core Concept**
Mitral stenosis is a valvular heart disease characterized by the narrowing of the mitral valve orifice, leading to obstruction of blood flow from the left atrium to the left ventricle. The resulting increase in left atrial pressure causes enlargement and hypertrophy of the left atrium, which can be visualized on chest radiographs.
**Why the Correct Answer is Right**
The double atrial shadow in mitral stenosis is due to the presence of a prominent left atrial appendage and the enlarged left atrium itself. The left atrial appendage is a small, finger-like projection of the left atrium that can be seen as a separate structure on chest radiographs. In mitral stenosis, the left atrium is enlarged, causing the left atrial appendage to become more prominent and visible as a double atrial shadow.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the anatomical changes that occur in mitral stenosis.
**Option B:** This option is incorrect because it refers to a condition that affects the right atrium, not the left atrium.
**Option C:** This option is incorrect because it is a description of a normal anatomical structure, not a pathologic change associated with mitral stenosis.
**Clinical Pearl / High-Yield Fact**
A double atrial shadow on chest radiograph is a classic sign of mitral stenosis. To remember this, recall that the "double atrium" is due to the enlarged left atrium and its appendage.
**Correct Answer:** A.