Section: New Results

Nonlinear dynamics and Mild Therapeutic Hypothermia (MTH)

Participants : Binbin Xu [correspondant], Oriol Pont, Hussein Yahia, Ihu Liryc.

The neurological damage after cardiac arrest constitutes a big challenge of hospital discharge. The mild therapeutic hypothermia (MTH) (34${}^{\circ }\mathrm{C}$ - 32${}^{\circ }\mathrm{C}$) has shown its benefit to reduce this type of damage. However, it can have many adverse effects, among which the cardiac-arrhythmia-generation-a-posteriori (CAGP) can represent up to $34\%$. So it's important to understand the mechanism of CAGP in order to improve this therapy. Our study with a cardiac culture in vitro showed that at 35${}^{\circ }\mathrm{C}$ the CAGP can be induced. Spiral waves, commonly considered as a sign of cardiac arrhythmia, are observed. The process of MTH can be represented by a Pitchfork bifurcation, which could explain the different ratio of arrhythmia among the adverse effects after this therapy. This nonlinear dynamics suggests that a variable speed of cooling / rewarming, especially when passing 35${}^{\circ }\mathrm{C}$, would help to decrease the ratio of post-hypothermia arrhythmia and then improve the hospital output. See figures 5 , 6 .

Figure 5. Phase space reconstruction for extracellular potential signals at 37${}^{\circ }\mathrm{C}$, 35${}^{\circ }\mathrm{C}$ and 33${}^{\circ }\mathrm{C}$.

Figure 6. Illustration of Bifurcation or Trifurcation (type Pitchfork) of hypothermia effect.

Publications: [33] , [35] , [39] .