An elderly patient with exertional syncope has a harsh crescendo-decrescendo systolic murmur best heard at the right second intercostal space. What is the most likely diagnosis?

• A. Calcific aortic stenosis
• B. Hypertrophic obstructive cardiomyopathy
• C. Aortic regurgitation
• D. Mitral stenosis

Answer: (A)

Recognizing the murmur pattern and the patient’s age and symptoms is key. A harsh, crescendo–decrescendo systolic murmur heard best at the right second intercostal space is classic for aortic stenosis, and in older adults the most common cause is calcific degeneration of the aortic valve. This valve narrowing creates a fixed obstruction to outflow from the left ventricle, so during exercise the heart can’t sufficiently increase forward flow. That limited ability to raise cerebral perfusion during activity explains exertional syncope.

The murmur’s location and radiation support this: it’s a systolic ejection murmur at the right upper sternal border, often radiating toward the carotids. In contrast, the other conditions present with different patterns or locations—mitral stenosis is a diastolic murmur at the apex; aortic regurgitation is a diastolic murmur best heard along the left sternal border; hypertrophic obstructive cardiomyopathy can cause syncope but typically has a murmur best heard at the left lower sternal border and changes with preload.