Thermodynamic consequences of a three-hour long anoxia were investigated on the isolated mammalian rat myocardium. The anoxic heart operated in a far-from-equilibrium manner as attested by the non-linearity between the thermodynamic force and the thermodynamic flow. When subjected to slight fluctuations due to anoxia, the open far-from-equilibrium cardiac system presented a thermodynamic bifurcation at ~ 60 minutes of anoxia. The bifurcation was characterized by a sudden change of direction in the bifurcation diagram of a one-dimensional nonlinear differential equation with one parameter and occurred at a non-hyperbolic fixed point at which moment the heart lost its thermodynamic stability. The parameter of the differential equation was the single force of the myosin molecular motor. These results helped to reflect a self-organized process and the occurrence of a dissipative structure. This offers valuable insights into our understanding of myocardial protection and could be of considerable interest, especially for heart transplants where the recipient must benefit from the donor's heart in the shortest possible time.
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