Another propagation of ‘light’ in the heart

A few weeks ago (back on February 27th) the cosmology group seminar took an unusual turn from outer to Inner Space. Sehun Chun, who’s a researcher at AIMS, gave us a fascinating talk on his work on electrical propagation in the heart.

After a quotation from Weyl, Sehun moved on to introducing us to the human heart and how it’s complexities are modelled with a combination of electricity, mechanics, elasticity and fluid mechanics. He then described some of the challenges of modelling the electric signal in the heart.

By using an analogy to a forest fire, Sehun explained that (like in the forest fire) energy is not conserved and does not depend on position, but rather on the media.

Moving on from analogies to maths, Sehun explained a few of the key mathematical ideas and techniques in his work. In particular he discussed the particular quirks of Maxwell’s equations, anisotropy and geometry when doing electrophysiology, explaining that there are several subtleties that arise when applying physics to the “light in the heart”.

The particular problem Sehun was is interested in is when propagation initially fails to stay on it’s normal track and comes back to re-excite the cardiac tissues (this is called a unidirectional pathway). Sehun explained that this can happen in the presence of scar tissue or other defects in the heart.

Sehun told us how the re-excitement could be studied by modelling the propagation of the electrical signal using a relative acceleration approach. Here (with help from another useful analogy involving buckets of water) the underlying idea is that if the relative acceleration of cardiac excitation becomes sufficiently large, the propagation stops.

After showing us the relevant equations, Sehun presented some results from his computational modelling which showed when unidirectional pathways could arise. The talk wrapped up with return to theory and a explanation of how the results fit in.

Throughout his stimulating talk, Sehun drew many comparisons between his work and more familiar physics problems, highlighting both the similarities and the differences and demonstrating that the riches of the universe are not just at the Hubble scale.

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