Total of 89 patients undergoing elective cardiac surgery will be enrolled.

Right CVC insertion begins at their intersection of the cricoid cartilage level and the triangular point where the sternal head of the SCM muscle meets the clavicular head. After insertion the central venous catheter through the right internal jugular vein and positioning it, the location of the tip of the central venous catheter will be confirmed by TEE.

Investigator confirms the location of the 2 cm from the junction between right atrium and superior vena cava to the end of the tip of the catheter using TEE, and measures the insertion depth of the catheter at insertion point. It is possible to find the ideal central venous catheter insertion depth in actual clinical practice in adult patient.

The ideal central venous catheter insertion depth can be measured accurately when the end of the central venous catheter is monitored with transesophageal ultrasonography, and it can be derived a meaningful formula for predicting the ideal central venous insertion depth from the patient's height .

Inclusion Criteria:

• adult patient over 18 years of age undergoing cardiac surgery under general anesthesia, requiring central venous catheter insertion through the right internal jugular vein and insertion of a TEE probe

Exclusion Criteria:

• Patients who disagree with the study.
• Patients who had difficulty in inserting the central line through the right internal jugular vein.