A 14-year-old female fainted while running and now feels light-headed. What condition might have caused her syncope?

The scenario presented involves a 14-year-old female who fainted while running and is now feeling light-headed, which are characteristic symptoms associated with syncope that can be related to cardiovascular factors.

Reduced atrial filling pressure is a significant contributor to syncope in young athletes, particularly during exertion. When a person is running or engaging in vigorous physical activities, blood flow is redistributed to the muscles and skin, which can lead to decreased return of blood to the heart and consequently reduced filling pressure in the right atrium. This reduction may result in insufficient volume entering the ventricles during diastole, leading to decreased cardiac output and subsequent loss of consciousness.

In the context of this question, it is important to recognize how strenuous activities can impact cardiovascular dynamics, especially in younger individuals who may not have fully developed the physiological adaptations to strenuous exercise. The phenomenon of reduced atrial filling pressure during physical activity can lead to transient hypotension, causing syncope, especially in a setting where blood flow is compromised.