What is the most common cause of a systolic ejection murmur?

• A. Mitral stenosis
• B. Pulmonary stenosis
• C. Aortic stenosis
• D. Aortic regurgitation

Answer: (C)

A systolic ejection murmur comes from turbulent blood flow through a semilunar valve during ventricular ejection. The classic cause here is narrowing of the aortic valve, which creates a crescendo-decrescendo murmur best heard at the right upper sternal border and that often radiates to the carotids. This is the most common source of a systolic ejection murmur among the options, typically arising from calcific degeneration with age or a bicuspid aortic valve in younger individuals. By contrast, mitral stenosis produces a diastolic rumble with an opening snap at the apex, and aortic regurgitation is a diastolic decrescendo murmur due to regurgitant flow back into the ventricle; pulmonary stenosis can cause a systolic murmur too, but it is far less common than aortic stenosis.