Randomization and interventions
A random number table will be generated using the SAS software and independently managed at the Inha University Hospital Cardiovascular Center. Study participants will be randomly assigned in a 1:1 ratio to a group that will receive intra-coronary nitrate before percutaneous coronary intervention (PCI) or a group that will not by the un-blinded coordinator. The result of random grouping (nitrate group or control group) will be placed inside sealed box.