A 65-year-old male with heart failure presents with a systolic murmur. What is a common underlying cause?

In the context of a 65-year-old male presenting with heart failure and a systolic murmur, the common underlying cause is mitral regurgitation. This condition typically arises from structural changes in the heart, such as dilation of the left ventricle or changes related to age, leading to improper closure of the mitral valve during systole.

Mitral regurgitation results in blood flowing backward into the left atrium when the left ventricle contracts, contributing to symptoms of heart failure, including shortness of breath and fatigue. The murmur associated with mitral regurgitation is a holosystolic (or pansystolic) murmur, which is best heard at the left lower sternal border.

While aortic stenosis, tricuspid regurgitation, and hypertrophic cardiomyopathy can also contribute to heart murmurs and heart failure, mitral regurgitation is particularly prevalent in older adults and has a strong correlation with the clinical scenario presented in the question. In older populations, degenerative changes and rheumatic heart disease can lead to the development of mitral regurgitation, making it more common in this age group compared to the other listed options.