a fluttering heartbeat的用法和样例：
- a fluttering heartbeat; palpitant movements rather than violent eruptions; my palpitating heart.
- Mother is all of a flutter because of thunder and lightning.
- There was a flutter of wings among the trees.
- I could feel a fluttering pulse.
- The news caused a flutter among the teaching staff.
- His arrival put the girls in a flutter.