1. School of clinical medicine, Weifang Medical University, Weifang, Shandong, China;
2. Department of Gastroenterology, Peking University Third Hospital, Beijing, China;
3. Department of Electrophysiology, The Affiliated Hospital of Weifang Medical College, Weifang, Shandong, China;
4. Department of Gastroenterology, The Affiliated Hospital Of Qingdao University, Qingdao, Shandong, China