The advanced practice registered nurse (APRN) examines an 92 year-old patient. The APRN notes a systolic ejection murmur (grade II out of VI), heard in the right upper sternal border and the right side off the neck. What is the most likely cause of the systolic murmur in this patient?

A. Aortic stenosis is correct because a systolic ejection murmur heard at the right upper sternal border that radiates to the carotid arteries is classic for aortic valve narrowing. This murmur is usually crescendo-decrescendo, medium-pitched, and occurs during systole as blood is ejected from the left ventricle through the narrowed aortic valve. It is especially common in elderly patients due to degenerative calcification. B. Right sided heart failure is incorrect because it is a clinical syndrome, not a valvular lesion. It may be associated with tricuspid regurgitation or pulmonary murmurs, which are best heard at the lower left sternal border, not the right upper sternal border with radiation to the neck. C. Tricuspid valve prolapse is incorrect because the tricuspid valve is located on the right side of the heart near the lower left sternal border. A systolic ejection murmur in the right upper sternal border is not consistent with tricuspid valve pathology. D. Mitral valve stenosis is incorrect because it produces a diastolic murmur best heard at the apex with the patient in left lateral decubitus position, often described as a low-pitched rumble, not a systolic ejection murmur radiating to the neck.