Canadian National Transplant Research Program 1 article published in JoVE Medicine Normothermic Ex Situ Heart Perfusion in Working Mode: Assessment of Cardiac Function and Metabolism Sanaz Hatami1, Christopher W. White1, Martin Ondrus1, Xiao Qi1, Max Buchko1, Sayed Himmat1, Lily Lin2, Katie Cameron3, David Nobes4, Hyun-Joong Chung5, Jayan Nagendran1,6, Darren H. Freed1,3,6,7 1Department of Surgery, Faculty of Medicine, University of Alberta, 2Department of Pediatrics, Faculty of Medicine, University of Alberta, 3Department of Biomedical Engineering, Faculty of Medicine, University of Alberta, 4Department of Mechanical Engineering, Faculty of Engineering, University of Alberta, 5Department of Chemical and Materials Engineering, Faculty of Engineering, University of Alberta, 6Canadian National Transplant Research Program, 7Department of Physiology, Faculty of Medicine, University of Alberta Normothermic ex situ heart perfusion (ESHP), preserves the heart in a beating, semi-physiologic state. When performed in a working mode, ESHP provides the opportunity to perform sophisticated assessments of donor heart function and organ viability. Here, we describe our method for myocardial performance evaluation during ESHP.