Abstract 410: Ultrafast Cooling Initiated By A Short And Safe Temperature-controlled Liquid Ventilation Abolishes Post-ischemic Myocardial Infarction And Contractile Dysfunction In Chronically Instrumented Rabbits
Introduction: Total liquid ventilation with temperature-controlled perfluorocarbons (TLV) induces an ultrafast cooling and was demonstrated to be cardioprotective if instituted at the onset of a 30 min coronary artery occlusion (CAO) in open-chest rabbits.
Hypothesis: Because it was difficult to revive rabbits exposed to prolonged TLV we hypothesized that rapid cooling with a short TLV episode and maintained by conventional external cooling would be better tolerated and still protective.
Methods: Rabbits were instrumented with a balloon occluder and piezoelectric crystals, assessing segment length (SL) shortening within the area at risk. Two weeks later, rabbits were reanesthetized and underwent a 30 min CAO with either normothermia (Control group, n = 6) or cooling from 5th min of CAO to the end of CAO. Cooling procedures were either conventional external cooling with ice filled cold blankets (CB group, n = 7) or ultrafast cooling initiated by 10 min TLV in addition to the cold blankets (TLV + CB group, n = 6). After reperfusion, animals were rewarmed and allowed to awaken. Follow-up of SL shortening was performed while conscious over 3 days before euthanasia and infarct size evaluation (TTC staining).
Results: Body core temperature was similar in all groups at baseline and was modestly reduced with CB vs TLV + CB (−2.2 ± 0.3 vs −4.4 ± 0.5°C at 25 min CAO, respectively). As shown in Table⇓, CB caused only modest protection against infarction and post-ischemic SL shortening depression, as compared to control. Conversely, TLV + CB virtually abolished these phenomena. Histology of TLV lungs revealed only mild congestion in 3/6 rabbits. Electron microscopy of samples performed in additional rabbits at the end of CAO showed a quiet complete preservation of cardiomyocyte ultrastructure with TLV + CB.
Conclusion: Short periods of TLV can be safely used for ultrafast cardiac cooling that elicit a potent protection against myocardial damage and contractile dysfunction.