The investigators are trying to evaluate the performance of neutrophil and lymphocyte counts as a risk factor of deep sternal wound infection after coronary artery bypass graft surgery.

Deep sternal wound infection after coronary artery bypass graft is a very dangerous complication as it prolongs hospital stay, increase morbidity and mortality, and increase cost of care.

As a risk factor of surgical site infection, risk index reported by NNIS (national nosocomial infection surveillance), Euroscore, or Society of thoracic surgeon risk score are currently used. However, as various performances are reported regarding these index or scoring systems, and many factors are needed for these index or scoring system, there is a need to develop a more simple risk factor with better performance. We focused on the differential blood cell count, as the neutrophil and lymphocyte count are related to the degree of surgical invasion, and inflammatory response. Previous studies reported that the neutrophilia or lymphopenia is related to postoperative infection. Therefore, we are trying to evaluate the performance of preoperative or postoperative the blood cell differential count as a risk factor for sternal wound infection after coronary artery bypass surgery.

Inclusion Criteria:

• Those underwent coronary artery bypass graft surgery with median sternotomy in Samsung Medical Center during the period of January 2008 and December 2011.

Exclusion Criteria:

• Those underwent coronary artery bypass graft surgery with mini-thoracotomy
• Those with insufficient study data recognized by electronic medical record

Those underwent coronary artery bypass graft surgery with median sternotomy in Samsung Medical Center during the period of January 2008 and December 2011.