What change occurs in left atrial size with mitral stenosis?

• A. Increase
• B. Decrease
• C. No change
• D. Variable

Answer: (A)

Mitral stenosis imposes a diastolic obstruction to flow from the left atrium into the ventricle, causing blood to back up into the pulmonary veins and raising left atrial pressure. Over time, the left atrium adapts by stretching and enlarging to accommodate the increased pressure and volume, so the left atrial size increases. This dilation is a common finding in chronic mitral stenosis and helps explain the higher risk of atrial fibrillation and thrombus formation. In contrast, a decrease or no change wouldn’t align with the pressure‑overload effect, and while acute MS can show variability, the typical long‑term change is an increased left atrial size.