Shu Zhang1, Da Zhu2, Zhi Wan1, Yu Cao3. 1. Department of Emergency medicine, West China Hospital, Sichuan University, Sichuan, PR China. 2. Department of Cardiovascular surgery, West China Hospital, Sichuan University, Sichuan, PR China. 3. Department of Emergency medicine, West China Hospital, Sichuan University, Sichuan, PR China. Electronic address: dr.yu.cao@gmail.com.