Which statement describes an accentuated S1?

• A. Tachycardia-induced: short PR interval with increased cardiac output
• B. Exercise, anemia and hyperthyroidism
• C. Mitral stenosis: open wide and then closes
• D. All of the above

Answer: (D)

Accentuation of the first heart sound occurs when the mitral and tricuspid valves close with unusually rapid or forceful closure at the start of systole. This is more likely when there is higher flow across the AV valves or a quicker rise in ventricular pressure, making the closure sound louder.

Tachycardia fits this because a shorter PR interval and faster heart rate bring atrial contraction into a tighter window before systole, and the brisk, forceful closure of the valves produces a louder S1. High-flow states across the AV valves also amplify S1: exercise, anemia, and hyperthyroidism all raise cardiac output and the velocity of blood filling and ejection, increasing the force of valve closure and thus the sound. Mitral stenosis can present with a loud S1 as well, since the leaflets—when they do close—can do so with abrupt, pronounced closure against the elevated left atrial pressure early in systole. Because each of these scenarios can heighten the closing sound of the AV valves, the result is an accentuated S1, making all of the listed situations potential contributors.