Beat/tempo equalization

This is probably a weird question, but I’m relatively new to audio processing (thus far, my idea of audio processing has been using the pitch shift to drop one guitar track by an octave since I can’t afford a bass).

Does Audacity have any tool built in to help equalize a beat?

I’m trying to record a lullaby for the funeral of a friend’s baby girl, and I want to use a heartbeat as the rhythm track. I found a great MP3 with a slow and almost-perfect-tempo heartbeat, but every now and then, the beat goes out of sync (naturally - even at rest the heartbeat is rarely going to stay at one rhythm for long). I would love to be able to equalize the beat so that it’s steady throughout.

Do I really need something like a drum autotune for this, or does Audacity have something that can pull this off?

Audacity has a “repeat” function:
if you select a short section of heartbeat which keeps perfect time, then repeat it, you will have a very regular heartbeat track.