In A Heartbeat Meaning

(idiomatic) Without hesitation or reservation; at once.

Example: 1989 Aug. 6, Claudia H. Deutsch, "Colgate's Next Trick: Controlling the Chaos," New York Times (retrieved 24 June 2011):
  â€œColgate would sell Princess House in a heartbeat, if it could find a buyer,” said Bonita Austin.
2001 May 22, Kyle Woodlief, "Sharp-shooting Swede Sjostrom shines," USA Today (retrieved 24 June 2011):
  Sjostrom's game is predicated on strong skating. He accelerates in a heartbeat with a lightning quick stride and changes direction smoothly.
2006 July 12, Steven Berlin Johnson, "Don't Fear the Digital," Time:
  [I]f I had to do away with either handwriting or typing for the rest of my life, I'd give up handwriting in a heartbeat.