An early diastolic decrescendo murmur best heard along the left sternal border suggests which lesion?

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An early diastolic decrescendo murmur heard best along the left sternal border is characteristic of aortic regurgitation. It comes from blood leaking backward from the aorta into the left ventricle as the heart relaxes in early diastole, when aortic pressure is higher than LV pressure. This creates a high‑pitched, blowing murmur that starts after the aortic valve should be closed and fades as diastole progresses. The left‑sided, left‑sternal-border location and the timing of the murmur (early diastole, decrescendo) distinguish AR from other lesions: mitral stenosis produces a diastolic murmur at the apex; aortic stenosis produces a systolic murmur at the right upper sternal border; tricuspid regurgitation is a holosystolic murmur at the left lower sternal border. AR murmurs are best heard with the patient sitting up and leaning forward, especially during expiration, and can be louder with maneuvers that raise systemic vascular resistance.