Final answer:
The correct diagnosis for a short systolic murmur at the cardiac apex that disappears with squatting is mitral valve prolapse. Squatting increases venous return, which may lessen the prolapse and thereby reduce or eliminate the murmur.
Step-by-step explanation:
The student's question pertains to a specific type of heart murmur characterized by being a short systolic murmur at the cardiac apex that disappears with squatting. In this situation, the correct diagnosis associated with these clinical findings is mitral valve prolapse (MVP). MVP occurs when one of the cusps of the mitral valve prolapses into the left atrium during systole, often producing a murmur that can change in intensity with body position. Squatting increases the venous return to the heart, which reduces the volume of the prolapsing valve tissue relative to the size of the left ventricle, hence, the murmur may disappear or diminish.
Hypertrophic cardiomyopathy is a condition characterized by the pathological enlargement of the heart, but it typically presents with a murmur that may become quieter with squatting due to the increased blood volume within the ventricle, making the obstruction caused by the enlarged heart muscle less pronounced. However, it is not typically associated with a disappearing murmur upon squatting.