Adult Echocardiography Practice Exam

Which heart sound is heard almost 100% of the time in patients with acute myocardial infarction?

1. A. s2

2. B. s1

3. C. s3

4. D. s4

The correct answer is: D. s4

In patients with acute myocardial infarction (AMI), the presence of the fourth heart sound, or S4, is commonly observed due to the pathological conditions that arise from myocardial ischemia. The S4 sound occurs as a result of atrial contraction against a stiff or hypertrophied ventricle, which is typically associated with impairments in ventricular compliance that can arise in the setting of AMI. The development of ischemic heart disease leads to chronic changes in the heart muscle, which includes potential hypertrophy or stiffness of the left ventricle. S4 is often described as a "tennessee" sound because it has a distinct cadence. Its consistent presence in the backdrop of an acute myocardial infarction is related to the compromised cardiac function that is frequently observed, as the heart struggles to fill adequately during diastole due to reduced contractility and compliance issues. In contrast, while S1 and S2 are normal heart sounds associated with valve closure and are largely variable in their presence and amplitude, S3 is associated with volume overload states and congestive heart failure, which may not always be present during the acute phase of an infarction. Thus, S4 serves as an important clinical indicator of the underlying cardiac changes associated with acute myocardial infar