Backtable heat-enhanced preconditioning: A simple and effective means of improving function of heart transplants

Background. Cardiac harvest teams are usually committed to immediately tran sfer the explanted donor heart into its cold storage solution. We tested th e opposite hypothesis that a brief prestorage episode of heat-enhanced isch emic preconditioning could be protective. Methods. Fifty-three isolated isovolumic rat hearts underwent 4 hours of co ld (4 degreesC) storage in the Celsior preservation solution and 2 hours of reperfusion. Control hearts were immediately immersed after arrest. Tn the 3 treated groups, 2 customized thermal probes were first applied onto the left ventricular free wall of the explanted heart at 22 degreesC, 37 degree sC or 42.5 degreesC for 15 minutes before immersion. Each of the selected t emperatures were monitored at the probe-tissue interface by a thermocouple. Results. Whereas base line end-diastolic pressure was set at not equal 8 mm Hg in all groups, it increased during reperfusion (mean +/- SEM) to 28 +/- 3, 27 +/- 3, 17 +/- 1, and 18 +/- 2 mm Hg in control, 22 degreesC, 37 degr eesC and 42.5 degreesC-heated hearts, respectively (37 degreesC and 42.5 de greesC: p < 0.05 versus controls and 22 degreesC). Slopes of pressure-volum e curves featured similar patterns. Likewise, reperfusion dP/dT (mm Hg/s(-1 )) was significantly lower in control and 22 degreesC hearts (1,119 +/- 114 and 1,076 +/- 125, respectively) than in those undergoing prestorage heati ng to 37 degreesC and 42.5 degreesC (1,545 +/- 109 and 1,719 +/- 111, p < 0 .05 and p < 0.01 versus controls and 22 degreesC, respectively). Western bl ot analysis of LV samples did not demonstrate any upregulation of HSP 72 in either group. Conversely, the involvement of preconditioning was evidenced by the loss of protection in the 42.5 degreesC-heated hearts when, in 2 ad ditional groups, the storage solution was supplemented with either the prot ein kinase C and tyrosine kinase inhibitors chelerythrine (5 mu mol/L) and genistein (50 mu mol/L) or the mitochondrial K-ATP channel inhibitor 5-hydr oxydecanoate (200 mu mol/L). Conclusions. A brief period of postexplant ischemia with enhancement by top ical heating ("backtable preconditioning") could be a simple and effective means of improving the functional recovery of heart transplants. (C) 2001 b y The Society of Thoracic Surgeons.