Collateralization causes confusion when interpreting a "normal stress test." Just because there is blood flow, and perfusion, and no signs of EKG changes, it doesn't mean anything. There is no way to determine which pathway the blood takes to deliver oxygen, and how badly occluded a singe vessel actually could be proximal to the collaterals that have formed.
For this reason, and if hospitals truly want to save money (as alluded to in the above posts), and maximize their revenue, and also provide exemplary care, I would think that using CATH as a gold standard test for ALL intermediate and above TIMI admissions would do several things - It will fix those with real disease immediately, it will identify those who will need close follow-up and likely repeat cath in 1 year, and it will reduce (in theory) the overall mortality in the community by reducing the number of MI's that result from undiagnosed disease.
I honestly see the Cath as the next colonoscopy in the a few years - especially with the upcoming readmission prevention and goal of disease prevention getting in the way of traditional hospital admission and observation. At the minimum, going to cath directly from the ED for those moderate to high risk patients may become more frequent - even with negative troponin values. The real question is, who is going to be available to perform those Caths...