Which preposition to use with heartbeat

of Occurrences 4%

It lowered the heartbeat of Lefty Joe to a tremendous, slow pulse.

at Occurrences 1%

" She could not follow him down the vista of fancy, but stood interrogating him with her heartbeats at her throat.

to Occurrences 1%

The last report and the crash of the front door slammed behind Dupont were as one heartbeat to the next.

Which preposition to use with  heartbeat