Conflicting responses to two ventricular entrainments in a narrow QRS tachycardia: What is the mechanism?Jeong-Wook Park, CEPS, Young Choi, MD, Sung-Hwan Kim, MD, Yong-Seog Oh, MDFrom the Division of Cardiology, Department of Internal Medicine, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea.