When might an S4 heart sound be heard?

• A. Increased left ventricular compliance
• B. Decreased left ventricular compliance
• C. Right ventricular hypertrophy
• D. Acute pericarditis

Answer: (B)

An S4 heart sound, often referred to as an "atrial gallop," typically occurs when there is increased resistance to filling of the ventricles, which is most commonly due to decreased left ventricular compliance. This decreased compliance can arise from conditions such as left ventricular hypertrophy, ischemic heart disease, or aging. In these cases, the ventricular wall becomes stiffer, leading to increased pressure during late diastole when the atria contract, producing the S4 sound.

The S4 sound is actually generated by the sound of blood being forced into a stiff ventricle. This makes it a marker of potential diastolic dysfunction. In patients with conditions that decrease the compliance of the left ventricle, the S4 sound can be a clinical sign that warrants further investigation into the heart's functioning and overall cardiovascular health.