The QTc interval is affected by heart rate, medications and changes in the autonomic nervous system. The endotracheal laryngoscopy, the necessary step during general anesthesia, prolongs QTc interval. Changes in the flow of ion currents could result from the genetic variation of myocardial ion channels by gene polymorphism. This study is to investigate the association of cardiac ion channel related gene polymorphism and prolonged QTc interval after endotracheal intubation in adult patients.

Inclusion Criteria:

1. 20-65 years old
2. scheduled for general anesthesia requiring direct laryngoscopy

Exclusion Criteria:

1. Patients taking antihypertensive medication (beta-blocker, CCB)
2. patients taking other medications known to affect QTc interval
3. Patients with abnormal ECG and prolonged QTc (>500 msec)
4. Diabetes, liver disease, kidney disease, heart failure, congenital heart disease
5. Severe electrolyte imbalance
6. illiterate, foreigners who cannot understand the consent form

20-65 years old, scheduled for general anesthesia requiring direct laryngoscopy