in a heartbeatAmerican EnglishAmE very quickly, without delay 一下子 Things can change in a heartbeat. 情况会瞬间发生变化。
in a heartbeat• If he asked me to marry him, I'd accept in a heartbeat.• Beyond Des Jardins' cooking, there are two things that would bring me back to Jardiniere in a heartbeat.• Don't think for a minute owner Jerry Jones wouldn't trade places with Bob McNair in a heartbeat.• For exam-ple, an emergency or operating room is not the best environment for monitoring subtle variations in heartbeats.
→ in a heartbeat at heartbeat(2)