Improved utilization of donor hearts would benefit chronic heart failure patients awaiting transplant. Limitations to cardiac allograft preservation include ischemic time, donor organ quality, and accurate graft assessment. We hypothesized that human hearts declined for transplant may be resuscitated after varied ischemic times. The unique studies performed within the Visible Heart® Laboratory for over two decades have provided unique insights relative to optimizing large mammalian functions post-cardioplegia.