When is S2 splitting considered normal?

S2 splitting is considered a normal finding during inspiration in young individuals due to the physiological changes that occur in the heart and circulatory system during this phase of respiration. When a young person inhales, the negative intrathoracic pressure causes an increase in venous return to the right atrium. This increased volume results in a slight delay in the closure of the pulmonary valve compared to the aortic valve, leading to the characteristic split of the second heart sound (S2).

This phenomenon is particularly common in young adults and children, as their hearts and respiratory systems are more adaptable to changes in demand. It reflects a normal regulatory response of the heart to accommodate increased blood flow to the lungs during breathing.

In contrast, S2 splitting is not expected to occur during physical exertion in adults, at all times in children, or during sleep in the elderly, as these conditions do not typically promote the same cardiovascular dynamics that occur with inspiration in younger individuals.