 General methods: This section describes our approach to investigating the specific aims. The study is a prospective, double blind, placebo-controlled trial to assess the efficacy of a selective endothelin type A receptor antagonist BQ-123, as adjunctive therapy for PCI for non ST elevation MI. The control group will receive placebo rather than another vasodilator in order to specifically elucidate the role of the endogenous endothelin system. 