The choice of a heartbeat as a cinematic transition is rooted in human biology. Our brains are hardwired to prioritize sounds related to survival, such as the rhythmic "lub-dub" of a pulse.

: By speeding up or slowing down this rhythm, sound designers can manipulate an audience’s own pulse rate, leading them to feel the character's panic or the "fading" of life.

Transition effects like those found on Mixkit allow editors to move from one shot to another without breaking the immersion of fear. Download Free Heartbeat Sound Effects - Mixkit