The S4 heart sound is best described as which of the following?

The S4 heart sound is best described as which of the following?

• A. Atrial contraction causing blood to hit a stiff left ventricle
• B. Rapid ventricular filling
• C. Opening of the aortic valve
• D. A continuous murmur

Answer: (A)

The S4 gallop is produced when the atrium contracts late in diastole to push blood into a ventricle that is stiff or noncompliant. Because the ventricle resists filling, this atrial kick creates vibrations in the ventricular walls that are transmitted to the chest, producing a low-pitched sound just before the first heart sound. This pattern is classically associated with conditions that increase left ventricular stiffness, such as long-standing hypertension, left ventricular hypertrophy, or cardiomyopathy. So the description that matches this mechanism—atrial contraction causing blood to hit a stiff left ventricle—best describes S4. By contrast, rapid ventricular filling describes an S3 gallop, opening of the aortic valve isn’t how an S4 is generated, and a continuous murmur is not a gallop at all.

The S4 gallop is produced when the atrium contracts late in diastole to push blood into a ventricle that is stiff or noncompliant. Because the ventricle resists filling, this atrial kick creates vibrations in the ventricular walls that are transmitted to the chest, producing a low-pitched sound just before the first heart sound. This pattern is classically associated with conditions that increase left ventricular stiffness, such as long-standing hypertension, left ventricular hypertrophy, or cardiomyopathy.

So the description that matches this mechanism—atrial contraction causing blood to hit a stiff left ventricle—best describes S4. By contrast, rapid ventricular filling describes an S3 gallop, opening of the aortic valve isn’t how an S4 is generated, and a continuous murmur is not a gallop at all.