A 64-year-old man has a high-pitched blowing systolic murmur best heard at the right lower scapula border. What condition is most likely indicated?

The presence of a high-pitched blowing systolic murmur, particularly one that is best heard at the right lower scapula border, strongly suggests the existence of a condition that involves significant regurgitation and backflow of blood through the heart. In this case, the description aligns well with mitral regurgitation.

Mitral regurgitation occurs when the mitral valve fails to close completely during systole, leading to backflow of blood from the left ventricle into the left atrium. This backflow can create a murmur that is characterized as high-pitched and blowing. The specific location of the murmur, being best heard at the right lower scapula border, is associated with the path of the regurgitant flow, which radiates to that area due to the anatomical position of the heart and the direction of the blood flow.

Understanding the characteristics of heart murmurs is essential in differential diagnosis, and in this scenario, the distinguishing factors point towards mitral regurgitation as the most likely condition indicated by the described murmur.