Adult Echocardiography Practice Exam

What event corresponds with the first heart sound, S1?

1. Closure of the mitral valve

2. Closure of the aortic valve

3. Opening of the mitral valve

4. Opening of the aortic valve

The correct answer is: Closure of the mitral valve

The first heart sound, S1, is primarily associated with the closure of the mitral valve. This sound occurs at the beginning of ventricular contraction (systole), when the ventricles fill with blood and then contract to pump blood out of the heart. As the pressure in the ventricles rises, it exceeds the pressure in the atria, causing the mitral valve to close to prevent backflow of blood. The closure of the mitral valve produces a characteristic sound, which is a key indicator of the heart's mechanical function. Understanding the physiological sequence helps to clarify this point: prior to the closure of the mitral valve, the heart is in diastole, where it fills with blood, and once the ventricles contract, S1 follows immediately as the mitral valve shuts. This is vital for proper hemodynamic function, as the closure of the mitral valve marks the start of ventricular systole and is crucial for effective blood ejection. The other options involve events that do not correspond to S1, such as the closure or opening of the aortic valve, which relates to the second heart sound, S2, or the opening of the mitral valve, which occurs during diastole when the ventricles are