All of the following statements about third Hea sound (S3) are true, except
**Core Concept**
A third heart sound (S3) is a low-frequency diastolic sound heard during early diastole, typically in the cardiac apex region. It is caused by the rapid filling of the ventricle during early diastole, which leads to the vibration of the ventricular walls.
**Why the Correct Answer is Right**
The correct answer is related to the characteristics and clinical significance of the S3 heart sound. A third heart sound is often associated with conditions that lead to an increase in ventricular volume, such as heart failure, cardiomyopathy, and mitral regurgitation. The S3 sound is caused by the rapid filling of the ventricle during early diastole, which leads to the vibration of the ventricular walls. This sound is often heard in patients with a rapid heart rate, as the increased heart rate allows for more time for ventricular filling during diastole.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because S3 is not a sign of aortic regurgitation. The characteristic sound of aortic regurgitation is a diastolic murmur.
**Option B:** Incorrect because S3 is not a sign of pericardial effusion. The characteristic sound of pericardial effusion is a pericardial rub.
**Option C:** Incorrect because S3 is not a sign of pulmonary embolism. The characteristic symptom of pulmonary embolism is sudden onset of dyspnea.
**Clinical Pearl / High-Yield Fact**
A third heart sound is often referred to as the "gallop rhythm" because it sounds like a galloping horse. The S3 sound is a high-yield fact for exam purposes, as it is often associated with conditions that lead to heart failure.
**Correct Answer: C. Pulmonary embolism is not typically associated with S3.