Vegetations on under-surface of A. V. valves are found in:
**Core Concept**
Vegetations on heart valves are a hallmark of infective endocarditis, a condition characterized by the colonization and growth of microorganisms on the valve surface. In this context, the location and orientation of the vegetations are crucial for diagnosis and understanding the pathophysiology.
**Why the Correct Answer is Right**
The under-surface of the Aortic Valve (AV) valves is a common site for the formation of vegetations in infective endocarditis. This is because the AV valves are subjected to high-pressure blood flow, creating a turbulent environment that facilitates the adherence and growth of microorganisms. The under-surface of the valve is also a site of high shear stress, which may contribute to the formation of vegetations. The presence of vegetations on the under-surface of the AV valves is a characteristic feature of certain types of infective endocarditis, particularly those caused by Staphylococcus aureus.
**Why Each Wrong Option is Incorrect**
* **Option A:** Vegetations on the under-surface of the Mitral Valve (MV) are more commonly associated with Libman-Sacks endocarditis, a condition seen in systemic lupus erythematosus.
* **Option B:** Vegetations on the under-surface of the Pulmonary Valve (PV) are less common and typically seen in cases of right-sided endocarditis.
* **Option C:** Vegetations on the under-surface of the Tricuspid Valve (TV) are more commonly associated with right-sided endocarditis, particularly in intravenous drug users.
**Clinical Pearl / High-Yield Fact**
The location and orientation of vegetations on heart valves are crucial for diagnosis and understanding the pathophysiology of infective endocarditis. Remember that the under-surface of the AV valves is a common site for vegetation formation, particularly in cases of Staphylococcus aureus endocarditis.
**Correct Answer: A. Vegetations on under-surface of Aortic Valve (AV) valves.**