Bioenergetic recovery processes of injured myocardium. We employed cervically transplanted nonworking myocardium to simulate the condition of a heart supported by a ventricular assist device, and to investigate the bioenergetic recovery processes of injured myocardium with 31P nuclear magnetic resonance (NMR) techniques. A heterotopic graft was placed in the cervical portion of a recipient rat. One week later, a control 31P NMR spectrum was obtained from the graft. On the same day, the aorta of the graft was clamped for 30 minutes at room temperature. After this procedure, 31P NMR measurements of the graft were performed for 1 week. The phosphocreatine (PCr)/Inorganic phosphate (Pi) ratio, and beta-phosphate from adenosine triphosphate (beta-ATP)/Pi ratio on the first and second day after injury were significantly lower than control (p less than 0.05). However, these ratios recovered to a significant extent on the third and fourth day. These results suggest that 3 or 4 days are required for bioenergetic recovery of reversibly injured myocardium, even under nonworking conditions. 