Final answer:
In a normal, healthy heart, S3 is rarely heard during diastole and may indicate various conditions. S4, on the other hand, occurs during ventricular systole and indicates left ventricular failure.
Step-by-step explanation:
In a normal, healthy heart, the heart sounds S3 and S4 are heard during different phases of the cardiac cycle. S3 is rarely heard in healthy individuals and may indicate blood flowing into the atria, blood sloshing back and forth in the ventricle, or tensing of the chordae tendineae. It may be heard during diastole, when the ventricles are relaxed and filling with blood from the atria.
On the other hand, S4 occurs prior to the first heart sound (S1) during ventricular systole. It is the result of the contraction of the atria pushing blood into a stiff or hypertrophic ventricle, indicating left ventricular failure.The S3 heart sound is associated with the early phase of ventricular diastole, when the ventricles are filling with blood. It is often a normal finding in young individuals but may signify pathological conditions such as congestive heart failure in older adults. The S4 heart sound occurs just before S1, during the end phase of ventricular diastole and right before ventricular systole, when the atria contract to complete the ventricular filling process. It is typically indicative of a stiff or hypertrophic ventricle and can be a sign of left ventricular failure.