1. School of Graduate Studies, Tianjin University of Traditional Chinese Medicine, Tianjin 301677, P.R. China
2. Department of Cardiology, Tianjin Union Medical Center, Nankai University Affiliated Hospital, Tianjin 300121, P.R. China
3. Department of Cardiology, Tianjin Da Gang Hospital, Tianjin 300270, P.R. China
4. Department of Ultrasound, Tianjin Union Medical Center, Nankai University Affiliated Hospital, Tianjin 300121, P.R. China