Describe the S4 heart sound.

Describe the S4 heart sound.

• A. Atrial contraction causing blood to hit a stiff left ventricle
• B. Rapid ventricular filling
• C. Opening of stenotic mitral valve
• D. Midsystolic murmur

Answer: (A)

S4 is a late diastolic sound produced when the atria contract and push blood into a ventricle that is stiff and noncompliant. This atrial kick into a noncompliant ventricle creates a low-frequency vibration heard best at the apex with the bell, typically in the left lateral decubitus position, just before S1. It signals reduced ventricular compliance and can be seen with LV hypertrophy, long-standing hypertension, diastolic dysfunction, or cardiomyopathy. The other descriptions don’t fit: rapid ventricular filling sounds describe S3, not S4; an opening of a stenotic mitral valve would produce an opening snap in early diastole; and a midsystolic murmur is heard during systole, not as a diastolic sound.

S4 is a late diastolic sound produced when the atria contract and push blood into a ventricle that is stiff and noncompliant. This atrial kick into a noncompliant ventricle creates a low-frequency vibration heard best at the apex with the bell, typically in the left lateral decubitus position, just before S1. It signals reduced ventricular compliance and can be seen with LV hypertrophy, long-standing hypertension, diastolic dysfunction, or cardiomyopathy.

The other descriptions don’t fit: rapid ventricular filling sounds describe S3, not S4; an opening of a stenotic mitral valve would produce an opening snap in early diastole; and a midsystolic murmur is heard during systole, not as a diastolic sound.