The patients who have undergone cardiac surgery have higher likelihood of postoperative cognitive dysfunction (POCD). The carotid intima-media thickness (IMT) is associated with cognitive dysfunction in the old. The aim of this study is to evaluate the effect of carotid IMT in patients undergoing OPCAB(off-pump coronary artery bypass surgery) on postoperative cognitive dysfunction. Two hundred twenty four patients, aged 20 to 79 years, scheduled for OPCAB will be divided into increased IMT (n=112) and normal IMT (n=112) group by preoperative B-mode ultrasonography. The cognitive function measured by K-MMSE, MOCA-K before the operation, and on the 7 day, 3 months after operation. The patients in the non-surgical group are measured three times: baseline, after 7days, after 3 months.

Inclusion Criteria:

- patients who are scheduled to undergo OPCAB

Exclusion Criteria:

• severe cognitive dysfunction
• disabling mental change disorder
• unable to communicate or speak Korean
• do not have carotid IMT measurement.

Patients who are schedued to undergo OPCAB