**1. Introduction**

The shortage of donors is a major limiting factor in cardiac transplantation [1]. To enlarge the donor pool, extended criteria heart donors, including those with older age, left ventricular hypertrophy, hepatitis B/C infection, donor/recipient size mismatch and prolonged ischemic time are often considered with acceptable outcomes [2]. Organ ischemic time was defined as the time between the aortic cross-clamp applied during procurement and heart reperfusion during heart implantation [3]. Donor hearts are now procured from longer distances; extending the cold ischemic time. The registry of the International Society for Heart and Lung Transplantation report in 2017 demonstrated an ischemic time < 4 hours was associated with improved survival at 30 days and 5 years compared with longer ischemic time [3]. Given older heart donors have been increasingly utilized. Studies have shown that the hearts of older donors are more sensitive to prolonged ischemic time compared to younger donors [4, 5]. Many new strategies have been developed to improve allograft preservation, and minimize the effect of ischemia reperfusion injury. For DCD donors, a period of warm ischemia occurs at the beginning when life support is discontinued. Recently, *ex-vivo* perfusion technology has been developed to minimize warm and cold ischemic times, enable

organ resuscitation, evaluation and facilitate long-distance organ transportation. This technology has facilitated the expansion of the donor pool.
