1. School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
2. Cardiovascular Center, Seoul National University Hospital, Seoul, Republic of Korea.
3. Division of Cardiology, Department of Internal Medicine, Seoul National University Hospital, Seoul, Republic of Korea.
4. SoC Platform Research Center, Korea Electronics Technology Institute, Seongnam 463-816, Republic of Korea.