You can't admit and cath everyone. (Well, you could, but I wouldn't recommend it.)
I learned from "expert opinion" (my malpractice-wary attendings in residency) that a stress test expires after 1 year. I've never found evidence to support this.
On the other hand, I learned from my patients that a stress test expires as soon as they stop the ECG tracing.
So, how do I reconcile these "facts", and see chest pain patients without going crazy? I divide them into 4 levels:
1 - If you know it's not ACS - Don't worry, don't test. (e.g.: the pain started in the back and moved to the front and they have zoster in a left-sided T6 distribution).
2 - If I know it's ACS - Ignore last month's stress test. Hell, ignore your troponin. Admit them. (e.g.: the 72 yo had CP while mowing the lawn, sat down to have a cigarette and was surprised when that didn't make it better, then became nauseated and almost passed out, at which point his brother brought him to the ED and now he has flipped t waves in contiguous leads).
3 - I could be ACS, but something else is much more likely - Test for that something else, if it's positive - treat, if it's negative, see #4.
4 - If you don't think it's ACS, but you don't want to loose a law suit - Do whatever is the culture for low-but-not-no-risk chest pain at your shop. At my shop that means observing those with stress tests over 1 year old.