What condition is indicated by a mid-systolic ejection murmur best heard at the left sternal border?

• A. Hypertrophic obstructive cardiomyopathy
• B. Aortic stenosis
• C. Mitral regurgitation
• D. Pulmonary hypertension

Answer: (A)

A mid-systolic ejection murmur best heard at the left sternal border is indicative of hypertrophic obstructive cardiomyopathy. In this condition, the thickening of the heart muscle (particularly the interventricular septum) can obstruct blood flow out of the left ventricle during systole. This obstruction leads to turbulence in blood flow, which generates the characteristic mid-systolic ejection murmur.

The location of the murmur is important; the left sternal border is a typical area where such murmurs are auscultated, as it correlates with the outflow tract. Patients with hypertrophic obstructive cardiomyopathy may also exhibit a dynamic component to the murmur that can change with maneuvers such as standing or performing the Valsalva maneuver, due to alterations in preload and the degree of obstruction.

In contrast, conditions like aortic stenosis typically produce a late-peaking systolic ejection murmur that is often best heard at the right second intercostal space, mitral regurgitation generally results in a holosystolic murmur best heard at the apex of the heart and may radiate to the left axilla, while pulmonary hypertension can lead to a systolic murmur