This is a randomized, single blind, controlled study of intracoronary cocktail injection before fractional flow reserve (FFR) measurement when guiding percutaneous coronary intervention (PCI) in patients with acute coronary syndrome (ACS). Patients with ACS will be randomized into the cocktail plus FFR guided group or the QCA guided group. The primary outcome of the cocktail II study is the composite of death, myocardial infarction, class IV heart failure and target vessel revascularization within 1 year. The secondary outcome of the cocktail II study include left ventricular function, quality of life, stroke or life-threatening bleeding within 1 year.