When is an increased S3 sound often considered normal?

An increased S3 sound is often considered normal in young adults and during late pregnancy due to the physiological changes occurring in these populations. In young adults, the heart's increased compliance and rapid filling can generate a loud S3, which reflects the high volume of blood entering the ventricles during early diastole. This phenomenon is often noticed in athletes or those who are physically fit, as their hearts usually pump more efficiently, leading to a heightened volume of blood flow.

During late pregnancy, the increased blood volume and cardiac output can also result in a louder S3 sound. This is due to the well-known hemodynamic changes that occur as the body accommodates the needs of both the mother and the developing fetus. Therefore, an increased S3 sound in these contexts is typically benign and can be attributed to the normal physiological adaptation to increased blood volume and circulation demands.