Mitochondrial Function After Normothermic Regional Perfusion or Direct Procurement Followed by Hypothermic Oxygenated Machine Perfusion in Heart Transplantation After Circulatory Death.

BACKGROUND: Strategies to minimize ischemic damage during heart transplantation (HTX) by donation after circulatory death (DCD) are warranted because the inevitable ischemic injury linked to DCD HTX deteriorates mitochondrial respiratory capacity and ultimately graft quality. This study aimed to examine the myocardial mitochondrial function during DCD HTX with hypothermic oxygenated machine perfusion (HOPE) and compare the effect of normothermic regional perfusion (NRP) with that of direct procurement and perfusion (DPP). METHODS: A porcine DCD HTX model was used with hearts subjected to either DPP (n = 6) or NRP (n = 7) followed by HOPE and orthotopic HTX. Mitochondrial respiratory function was analyzed by high-resolution respirometry in left ventricle biopsies at baseline, after 180 min of HOPE, and after 60 min of reperfusion post-HTX. RESULTS: Mitochondrial oxidative phosphorylation (P = 0.0008), respiratory control ratio (P = 0.04), and coupling efficiency (P = 0.04) declined during DCD HTX. Fatty acid oxidation was preserved after 3 h of HOPE with a modest, statistically nonsignificant decline after reperfusion (P = 0.2). Oxidative phosphorylation was inversely correlated with troponin-T levels (r = -0.70, P = 0.0004). No statistically significant difference in mitochondrial respiratory capacity was observed between participants exposed to NRP and DPP. CONCLUSIONS: Mitochondrial respiratory capacity declined gradually throughout the course of DCD HTX and correlated with the degree of myocardial damage. Following HOPE, the extent of mitochondrial deterioration was comparable between NRP and DPP.

Effects of ketone body 3-hydroxybutyrate on cardiac and mitochondrial function during donation after circulatory death heart transplantation.

Normothermic regional perfusion (NRP) allows assessment of therapeutic interventions prior to donation after circulatory death transplantation. Sodium-3-hydroxybutyrate (3-OHB) increases cardiac output in heart failure patients and diminishes ischemia-reperfusion injury, presumably by improving mitochondrial metabolism. We investigated effects of 3-OHB on cardiac and mitochondrial function in transplanted hearts and in cardiac organoids. Donor pigs (n = 14) underwent circulatory death followed by NRP. Following static cold storage, hearts were transplanted into recipient pigs. 3-OHB or Ringer's acetate infusions were initiated during NRP and after transplantation. We evaluated hemodynamics and mitochondrial function. 3-OHB mediated effects on contractility, relaxation, calcium, and conduction were tested in cardiac organoids from human pluripotent stem cells. Following NRP, 3-OHB increased cardiac output (P < 0.0001) by increasing stroke volume (P = 0.006), dP/dt (P = 0.02) and reducing arterial elastance (P = 0.02). Following transplantation, infusion of 3-OHB maintained mitochondrial respiration (P = 0.009) but caused inotropy-resistant vasoplegia that prevented weaning. In cardiac organoids, 3-OHB increased contraction amplitude (P = 0.002) and shortened contraction duration (P = 0.013) without affecting calcium handling or conduction velocity. 3-OHB had beneficial cardiac effects and may have a potential to secure cardiac function during heart transplantation. Further studies are needed to optimize administration practice in donors and recipients and to validate the effect on mitochondrial function.