Acceptable Heartrate for Preemies?

[mommy2be412]

I was told and I can't remember exactly but something like a preemie baby's acceptable heart rate for under 35 weeks is 120-180 and at 35 weeks its 70-can't remember the number. Does anyone know for sure what the acceptable range is based on preemie baby's age? Or have a link with the information, I couldn't find anything.