What distinguishes the murmur of aortic stenosis (AS) from that of mitral regurgitation (MR)?

The characteristic that distinguishes the murmur of aortic stenosis from that of mitral regurgitation is related to the location and radiation of the murmur. Aortic stenosis typically produces a systolic ejection murmur that is best heard at the right second intercostal space and often radiates to the carotid arteries. This radiation occurs due to the direction of blood flow across the narrowed aortic valve, which is directed upwards toward the carotids.

In contrast, mitral regurgitation creates a holosystolic (or pansystolic) murmur that is best heard at the apex of the heart and usually does not have a significant radiation pattern to the carotids. Instead, this murmur may be transmitted to the left axilla or heard prominently at the left lower sternal border.

While mitral regurgitation can be associated with advanced age, it is not specifically more common in the elderly compared to aortic stenosis, as both conditions can present with age-related valvular changes. Aortic stenosis is also not best heard at the apex, but rather at the right second intercostal space, and the sound of mitral regurgitation is often described as a blowing or holosyst