Which of the following complications is indicated by a third heart sound (S3)?
A. Ventricular dilation
B. Systemic hypertension
C. Aortic valve malfunction
D. Increased atrial contractions
Correct Answer: A. Ventricular dilation
Rapid filling of the ventricle causes vasodilation that is auscultated as S3. The third heart sound (S3) is a low-frequency, brief vibration occurring in early diastole at the end of the rapid diastolic filling period of the right or left ventricle. This sound is dull, much more so than the normal sound. It is a shock, a perceptible elevation; it is hardly a sound.
Option B: A left-sided fourth heart sound is frequently present in patients with systemic hypertension, aortic stenosis, or hypertrophic cardiomyopathy. A left ventricular fourth heart sound is common also in patients with coronary heart disease. Here, the decrease in ventricular compliance can be the result of prior myocardial infarction or acute ischemia.
Option C: Aortic valve malfunction is heard as a murmur. Aortic stenosis is caused by narrowing the aortic valve and is the most common valvular pathology in the developed world. Typically, the stenosis arises from senile calcification or a congenital anomaly, such as a bicuspid aortic valve. Less commonly, rheumatic heart disease can affect the aortic valve. The characteristic crescendo-decrescendo systolic murmur is auscultated at the right upper sternal border and may radiate to the carotid arteries.
Option D: Increased atrial contraction can result in a fourth heart sound. Right ventricular fourth heart sounds occur in clinical situations in which the compliance of that chamber is reduced. Hence, significant pulmonic valve stenosis and pulmonary arterial hypertension are typically accompanied by a right ventricular fourth heart sound.
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