Atrial fibrillation (Af) is the most common morbid event after open heart surgery. Its incidence ranges from 19% to 27%, as reported by the Society of Thoracic Surgeons database. Many groups have tried to understand and treat this difficult problem and have formulated different hypotheses to explain its origin. An imbalance of the autonomic nervous system after surgical intervention has been accepted as a major determinant for this morbidity. Ventral cardiac denervation is a fast and low-risk procedure. This intervention has shown significantly reduction of the incidence and severity of Af after routine coronary artery bypass surgery. This technique could be applied both on-pump or off-pump and used as an adjunctive procedure to achieve Af prophylaxsis. However, the detailed mechanism remains unclear. Theoretically, heart receives its innervation from the autonomic nervous system (ANS) via the great vessels and pericardial attachment. The propensity and distribution of ANS nerve fibers are different in location. In this study, we would like to evaluate the ANS function after ventral cardiac denervation by using heart rate variability (HRV) and baroreflex (BRS) sensitivity. 30 patients proposed to have elective off-pump coronary artery bypass surgery are enrolled. After induction of anesthesia, the depth of anesthesia is controlled by inhalation agents and monitored by bispectral index. After the major cardiac operation, ventral cardiac denervation is performed by using electrocautery. The digital signals of heart rate and blood pressure are acquired before and after the surgical procedures under the same range of bispectral index (50~60). The paired HRV and BRS are analyzed. This will provide us more information to justify the procedure.