Final answer:
The third heart sound (S3) occurs after S2 during ventricle filling and may indicate normal physiology in young or physically active individuals, or pathological conditions like heart failure if present in later life.
Step-by-step explanation:
The third heart sound (S3) typically occurs shortly after the second heart sound (S2), during the rapid filling phase of the ventricles. In a healthy heart, S3 is usually not heard, but it may become audible in certain conditions, such as in younger individuals, athletes, and pregnant women. However, if present later in life, it could indicate a pathological condition like congestive heart failure, thus necessitating a medical assessment.
While S1 and S2 sounds are common and represent the closing of atrioventricular and semilunar valves respectively, S3 is associated with the blood flow dynamics during ventricular filling and may be part of a rhythm known as the "Kentucky gallop" when occurring with S1 and S2. It is essential for healthcare professionals to interpret the presence and quality of S3 correctly, as it can have significant diagnostic implications.It can indicate congestive heart failure if heard later in life. Some cardiologists refer to the collective sounds S₁, S₂, and S₃ as the 'Kentucky gallop.'