title: Efficacy of mechanical postconditioning following warm, global ischaemia depends on circulating fatty acid levels in an isolated, working rat heart model†.
abstract: OBJECTIVE
  The number of heart transplantations is limited by donor organ availability. Donation after circulatory determination of death (DCDD) could significantly improve graft availability; however, organs undergo warm ischaemia followed by reperfusion, leading to tissue damage. Laboratory studies suggest that mechanical postconditioning [(MPC); brief, intermittent periods of ischaemia at the onset of reperfusion] can limit reperfusion injury; however, clinical translation has been disappointing. We hypothesized that MPC-induced cardioprotection depends on fatty acid levels at reperfusion.
  
  
  METHODS
  Experiments were performed with an isolated rat heart model of DCDD. Hearts of male Wistar rats (n = 42) underwent working-mode perfusion for 20 min (baseline), 27 min of global ischaemia and 60 min reperfusion with or without MPC (two cycles of 30 s reperfusion/30 s ischaemia) in the presence or absence of high fat [(HF); 1.2 mM palmitate]. Haemodynamic parameters, necrosis factors and oxygen consumption (O2C) were assessed. Recovery rate was calculated as the value at 60 min reperfusion expressed as a percentage of the mean baseline value. The Kruskal-Wallis test was used to provide an overview of differences between experimental groups, and pairwise comparisons were performed to compare specific time points of interest for parameters with significant overall results.
  
  
  RESULTS
  Percent recovery of left ventricular (LV) work [developed pressure (DP)-heart rate product] at 60 min reperfusion was higher in hearts reperfused without fat versus with fat (58 ± 8 vs 23 ± 26%, P < 0.01) in the absence of MPC. In the absence of fat, MPC did not affect post-ischaemic haemodynamic recovery. Among the hearts reperfused with HF, two significantly different subgroups emerged according to recovery of LV work: low recovery (LoR) and high recovery (HiR) subgroups. At 60 min reperfusion, recovery was increased with MPC versus no MPC for LV work (79 ± 6 vs 55 ± 7, respectively; P < 0.05) in HiR subgroups and for DP (40 ± 27 vs 4 ± 2%), dP/dtmax (37 ± 24 vs 5 ± 3%) and dP/dtmin (33 ± 21 vs 5 ± 4%; P < 0.01 for all) in LoR subgroups.
  
  
  CONCLUSIONS
  Effects of MPC depend on energy substrate availability; MPC increased recovery of LV work in the presence, but not in the absence, of HF. Controlled reperfusion may be useful for therapeutic strategies aimed at improving post-ischaemic recovery of cardiac DCDD grafts, and ultimately in increasing donor heart availability.
authors.affiliation: Department of Cardiovascular Surgery, Inselspital, Berne University Hospital and University of Berne, Berne, Switzerland.
authors.forename: Maris
authors.initials: M
authors.lastname: Bartkevics
authors.affiliation: Department of Cardiovascular Surgery, Inselspital, Berne University Hospital and University of Berne, Berne, Switzerland.
authors.forename: Simon
authors.initials: S
authors.lastname: Huber
authors.affiliation: Department of Cardiovascular Surgery, Inselspital, Berne University Hospital and University of Berne, Berne, Switzerland.
authors.forename: Veronika
authors.initials: V
authors.lastname: Mathys
authors.affiliation: Department of Cardiovascular Surgery, Inselspital, Berne University Hospital and University of Berne, Berne, Switzerland.
authors.forename: Joevin
authors.initials: J
authors.lastname: Sourdon
authors.affiliation: Department of Cardiovascular Surgery, Inselspital, Berne University Hospital and University of Berne, Berne, Switzerland.
authors.forename: Monika
authors.initials: M
authors.lastname: Dornbierer
authors.affiliation: Department of Cardiovascular Surgery, Inselspital, Berne University Hospital and University of Berne, Berne, Switzerland.
authors.forename: Natalia
authors.initials: N
authors.lastname: Carmona Mendez
authors.affiliation: Department of Cardiovascular Surgery, Inselspital, Berne University Hospital and University of Berne, Berne, Switzerland.
authors.forename: Brigitta
authors.initials: B
authors.lastname: Gahl
authors.affiliation: Department of Cardiovascular Surgery, Inselspital, Berne University Hospital and University of Berne, Berne, Switzerland.
authors.forename: Thierry P
authors.initials: TP
authors.lastname: Carrel
authors.affiliation: Department of Cardiovascular Surgery, Inselspital, Berne University Hospital and University of Berne, Berne, Switzerland hendrik.tevaearai@insel.ch.
authors.forename: Hendrik T
authors.initials: HT
authors.lastname: Tevaearai Stahel
authors.affiliation: Department of Cardiovascular Surgery, Inselspital, Berne University Hospital and University of Berne, Berne, Switzerland.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Longnus
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005227:Fatty Acids / Q000097:blood*; D006084:Graft Rejection; D006085:Graft Survival; D016027:Heart Transplantation / Q000379:methods* / Q000401:mortality; D008297:Male; D015425:Myocardial Reperfusion / Q000009:adverse effects / Q000379:methods; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control*; D009926:Organ Preservation / Q000379:methods*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D015996:Survival Rate; D014019:Tissue Donors; D052096:Warm Ischemia / Q000009:adverse effects* / Q000379:methods
chemical_list: D005227:Fatty Acids
keywords: Cardiac ischaemia–reperfusion; Circulating fatty acids; Donation after circulatory determination of death; Heart transplantation; Mechanical postconditioning