What is indicated by the presence of an S4 heart sound?

The presence of an S4 heart sound is primarily associated with left ventricular hypertrophy. This sound, often referred to as an "atrial gallop," occurs due to the vibration of the ventricular wall when blood is forcefully filled into the left ventricle, which is often seen in conditions where the ventricle has thickened walls, such as in hypertensive heart disease or aortic stenosis.

In many cases, the S4 sound is an indicator of decreased ventricular compliance—the heart's reduced ability to fill properly because of its hypertrophied state. It typically presents before the S1 heart sound, indicating that the atria are contracting and pushing blood into a stiff ventricle.

The relationship of S4 with other conditions: while it can be present in heart failure and coronary artery disease, those conditions do not specifically point to the increased stiffness and hypertrophy associated with an S4 sound. Atrial fibrillation is characterized by an irregular heart rhythm and does not typically produce an S4, as it disrupts the normal sequence of filling and contraction of the heart. Thus, the existence of an S4 heart sound is most definitively connected to left ventricular hypertrophy.