**Question:** Iris shadow is sign of

A. Aortic regurgitation
B. Mitral stenosis
C. Pulmonary artery hypertension
D. Right ventricular failure

**Core Concept:** Iris shadow is a visualization of the iris, the colored part of the eye, through the anterior chamber of the eye. In clinical cardiology, it is used as a non-invasive method to evaluate cardiac structures and functions.

**Why the Correct Answer is Right:**
Correct Answer: B. Mitral stenosis

The iris shadow sign is typically observed in conditions that affect the heart valves or cause myocardial dysfunction. Mitral stenosis is a valvular heart disease where the mitral valve becomes narrowed and thickened, leading to reduced blood flow from the left atrium to the left ventricle. This results in an increased pressure gradient across the mitral valve, and the iris shadow sign is indicative of this increased pressure and narrowing of the mitral orifice.

**Why Each Wrong Option is Incorrect:**

A. Aortic regurgitation (option A): In aortic regurgitation, the aortic valve doesn't close properly, leading to a backflow of blood into the left ventricle. There is no significant increase in pressure gradient across the aortic valve, so the iris shadow sign is not expected.

C. Pulmonary artery hypertension (option C): Pulmonary artery hypertension is a condition characterized by elevated pulmonary artery pressure. The iris shadow sign is not directly related to pulmonary artery hypertension but rather reflects mitral valve dysfunction.

D. Right ventricular failure (option D): Right ventricular dysfunction may cause right-sided heart failure, but it is not directly related to the iris shadow sign. The iris shadow sign specifically indicates mitral valve dysfunction.

**Clinical Pearl:**

The iris shadow sign is a useful clinical sign to consider in the presence of suspected mitral stenosis, particularly when combined with other clinical and echocardiographic findings. It is important for clinicians to recognize this sign to initiate appropriate management and referral for further evaluation.

In summary, the iris shadow sign is a valuable clinical finding that helps identify increased pressure gradients across the mitral valve due to conditions like mitral stenosis. This sign is distinct from other heart conditions like aortic regurgitation, pulmonary artery hypertension, and right ventricular failure, which are not directly associated with the iris shadow sign.