1. Department of Cardiovascular Medicine, Nephrology, and Neurology, Graduate School of Medicine, University of the Ryukyus , 207 Uehara, Nishihara Town, Okinawa 903-0215 , Japan
2. Department of Cardiovascular Medicine, Tokushima University Hospital , 2-50-1 Kuramoto, Tokushima 770-8503 , Japan
3. Department of Radiological Technology, Graduate School of Medical Care and Technology, Teikyo University , Tokyo , Japan
4. Ultrasound Examination Center, Tokushima University Hospital , Tokushima , Japan
5. Department of Cardiology, Faculty of Medicine, University of Tsukuba , Tsukuba , Japan
6. Department of Cardiology, Graduate School of Medical Sciences, Nagoya City University , Nagoya , Japan