**Core Concept**
Sub-valvular aortic stenosis (SVAS) is a congenital heart defect characterized by the narrowing of the left ventricular outflow tract below the aortic valve. This narrowing can lead to obstruction of blood flow from the left ventricle to the aorta, resulting in symptoms such as exertional chest pain, syncope, and heart failure.

**Why the Correct Answer is Right**
Tricuspid valve atresia is a congenital heart defect characterized by the absence or closure of the tricuspid valve, which prevents blood from flowing from the right atrium to the right ventricle. This condition is not directly related to the pathophysiology of sub-valvular aortic stenosis, which primarily affects the left ventricular outflow tract. The other options, aortic regurgitation, coarctation of the aorta, and ventricular septal defect, can be associated with sub-valvular aortic stenosis due to their proximity to the left ventricular outflow tract and potential for shared embryological or hemodynamic mechanisms.

**Why Each Wrong Option is Incorrect**
**Option A:** Aortic regurgitation can occur in conjunction with sub-valvular aortic stenosis due to the increased pressure and stress on the aortic valve and root.

**Option B:** Coarctation of the aorta, a narrowing of the aortic isthmus, can be associated with sub-valvular aortic stenosis, as both conditions can result from abnormal embryological development of the aortic arch.

**Option D:** Ventricular septal defect (VSD) can be associated with sub-valvular aortic stenosis, as the increased flow through the left ventricle can contribute to the development of outflow tract obstruction.

**Clinical Pearl / High-Yield Fact**
Sub-valvular aortic stenosis is often associated with a characteristic "gooseneck" deformity of the left ventricular outflow tract on echocardiography. This deformity is due to the narrowing of the outflow tract and can be a key diagnostic feature of the condition.

**✓ Correct Answer: C. Tricuspid Valve Atresia**