A nationwide retrospective cohort study. To investigate the long-term patterns of transfusion and clinical outcomes of patients undergoing PCI.

A nationwide retrospective cohort study. Transfusion after PCI may increase a risk, but the long term effects after red blood cell transfusion is known. Longitudinal data is collected from administrative claims in the National Healthcare Insurance Service of Korea. All Korean patient date undergoing PCI inserting stent from January 1, 2011 to December 31, 2011 is extracted. Clinical outcomes until December 31, 2016 is investigated.

Primary outcome is the incidence density of red blood cell transfusion. Secondary outcomes are the association of transfusion with major adverse clinical event (MACE) consisting all-cause death, revascularization, critically ill cardiovascular status, or stroke.

Incidence density and time-dependent Cox proportional hazard regression is statistically analyzed.

Inclusion Criteria:

• All Korean patients undergoing PCI using stent from January 1, 2011 to December 31, 2011

Exclusion Criteria:

• Patients without any stent insertion

All patients undergoing PCI using stent in 2011 from all medical providers in Korea is selected using National Healthcare Insurance System