Ticagrelor increases circulating adenosine by reducing cellular re-uptake. Adenosine is a cardioprotective agent that utilizes cellular survival kinase pathways that may have beneficial effects on the microcirculation and myocardium in patients presenting with STEMI. Adenosine is currently used as a treatment for no-reflow and improves MVO post-STEMI when administered during PPCI. A recent study of healthy volunteers has confirmed that non-invasive coronary flow is augmented by ticagrelor and that this is mediated by adenosine. The Investigators propose that the very early beneficial effects of Ticagrelor in ACS may be adenosine mediated cardioprotection, rather than only due to an antiplatelet effect. This important research is original and a natural progression of the ticagrelor story. It expands the adenosine hypothesis and mode of action of ticagrelor and addresses a novel cardioprotective/ microcirculatory mechanism of action.