1. Heart Research Institute, Chung-Ang University College of Medicine, Seoul, Korea.
2. Department of Anesthesiology and Pain Medicine, Chung-Ang University College of Medicine, Seoul, Korea.
3. Department of Thoracic and Cardiovascular Surgery, Chung-Ang University College of Medicine, Seoul, Korea.
4. Department of Cardiology, Chung-Ang University College of Medicine, Seoul, Korea.
5. Department of Surgery, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.