**Question:** A young basketball player with height of 188 cm and arm span of 197 cm has a diastolic murmur best heard in the second right intercostal space: likely cause of murmur is:

A. Mitral stenosis
B. Aortic stenosis
C. Mitral regurgitation
D. Aortic incompetence

**Correct Answer:** C. Mitral regurgitation

**Core Concept:**
Diastolic murmurs are heard during the diastolic phase of the cardiac cycle, typically in the second or third left intercostal space, at the left sternal border, or in the left suprasternal notch. They are caused by a defect in the mitral valve or left atrium.

**Why the Correct Answer is Right:**
In this case, the diastolic murmur is heard in the second right intercostal space. This is most consistent with mitral regurgitation, where the regurgitant flow is directed towards the right side of the heart.

**Why Each Wrong Option is Incorrect:**
A. Mitral stenosis (option A) would produce a systolic murmur heard in the second left intercostal space, at the left sternal border, or in the left suprasternal notch.
B. Aortic stenosis (option B) causes a systolic murmur heard in the aortic area (second left intercostal space, left sternal border, or left suprasternal notch).
D. Aortic incompetence (option D) produces a systolic murmur heard in the aortic area (second left intercostal space, left sternal border, or left suprasternal notch).

**Clinical Pearl:**
The correct location of the murmur helps differentiate between mitral regurgitation (second right intercostal space) and aortic incompetence (second left intercostal space). Additionally, knowing the typical murmur locations for mitral stenosis and aortic stenosis can help you distinguish between these conditions as well.

**Core Concept:**
Diastolic murmurs are generally associated with valvular heart diseases. They are typically caused by valvular regurgitation or dysfunction, leading to increased blood flow through the heart chambers during diastole.

**Why Each Wrong Option is Incorrect:**
Mitral stenosis (option A) and aortic stenosis (option B) cause systolic murmurs, which are heard in different locations than diastolic murmurs. Mitral stenosis produces a systolic murmur in the left side, while aortic stenosis produces a systolic murmur in the left side.

**Why the Correct Answer is Right:**
The diastolic murmur in the second right intercostal space is due to mitral regurgitation. Mitral regurgitation occurs when the mitral valve does not close properly during diastole, leading to blood flowing back into the left atrium from the left ventricle. This results in increased blood flow through the heart chambers during diastole, which produces the diastolic murmur.

**Clinical Pearl:**