(your) heart skips a beat

you are suddenly surprised, excited, or frightened.

Ben walked into the room and her heart skipped a beat.

When the shark came toward us, my heart stood still.

• under the wire
• under thumb
• under wing
• under wraps
• under your belt
• under your breath
• under your nose
• under your own steam
• under your wing
• until are blue in the face
• until hell freezes over
• until kingdom come
• until the cows come home
• until you are blue in the face
• up against
• up against someone
• up against something
• up alley
• up and around
• up and coming
• up-and-coming
• up and running
• up a storm
• up a tree
• up for grabs