If your heart/mind/pulse races it works extremely fast because of excitement, drugs, illness, etc.

She was hot and sweaty and had a racing heart. 她热得汗流浃背，心怦怦狂跳。

A glimpse of his bare torso set my pulse racing. 我瞥了一眼他赤裸的躯干，顿时感到血脉贲张。