What does S4 heart sound indicate?

The S4 heart sound, often described as a "tennessee" sound due to its cadence, is typically associated with a stiff or hypertrophied ventricle, which is often a sign of diastolic dysfunction. This sound occurs just before the first heart sound (S1) and is produced by the atria contracting against a stiff ventricle during the last phase of diastole.

While it can be heard in a variety of clinical contexts, the presence of S4 is most frequently seen in conditions such as hypertension, aortic stenosis, or ischemic heart disease. Therefore, its significance is more aligned with heart-related issues rather than being exclusive to sinus rhythms, normal heart rhythms, or increased heart rates.

The idea that S4 is "only heard in sinus rhythms" is misleading, as S4 can be found in various arrhythmias and not solely in sinus rhythm. Therefore, S4 is more indicative of underlying cardiac conditions, particularly those that lead to some degree of diastolic dysfunction, making the interpretation of S4 sound a critical component of cardiac assessment.