**5.** *Ex-vivo* **organ perfusion**

One of the shortcomings of cold preservation is limited cold ischemic time, with 4 hours generally accepted as safe. The ISHLT database demonstrated that ischemic

times beyond 6 hours are associated with graft dysfunction and increased postoperative mortality [32]. *Ex-vivo* heart perfusion was developed based on the Langendorff perfusion model which demonstrated perfusing of coronary arteries was able to resuscitate a dead heart. Based on this concept, a commercial normothermic *Ex-vivo* heart perfusion system (Transmedics Organ Care System, OCS) was developed and recently FDA approved following many clinical trials. Due to its normothermic physiology, the cold ischemic time is lessened while using this platform.
