Yes we have a critical value.

We don'n normally phone troponins. They are an urgent test and we
expect the wards of A&E to check the hospital conputer regularly for
the results.

In England casualty deparments are penalised if the patient is in the
department  more than 4 hours and they are usually keen on getting the
results. They phone if the result is not ready quickly.

We don't report elevated Troponins as a Critical Value.
PjS

We call critical Troponin I >0.5. But only on admission or on the first
sample. After that the repeats are not considered critical even if they
are still elevated.

We call the first positive trop (=>0.5) to everyone except ICU. I guess
they
are on top of things enough.

Yes we call critical Troponin values to the floor.

One note on our calling critical troponin values to the floor.  At our  
hospital we have had a problem with nurses mischarting patient results so  
we have been required to call all critical (i.e. elevated) troponin values  
to the floor and record the nurses name and time of the call.  I realize  
calling more than the admission or initially elevated troponin value  
doesn't seem practical, but I am not sure there has been enough data  
collected on point to point troponin changes to determine their  
significance for any individual patient other than those studies which  
given general data concerning 30 day survival.