This is a cutaway view of a Icealos heart.
Notice that is six chambered.
A Icealos's blood is thick. Not quit as viscous as cold syrup, but close.
Also, their increased size necessitates the need for such a design.
Sure, earth mammals have varying sizes of 4 chambered hearts, but this is not a Earth Mammal. Not even a Mammal.
Also, A Icealos needs a larger, more complex heart to supply oxygen to its muscles and the like. A Icealos can reach their peak speed and maintain it for a long time. Times vary upon individuals.
Icealos species is copyright to me.

I used this as a ref: http://www.powayusd.com/teachers/ms.....artDiagram.jpg
Again I darkened it with my scanner so it would show better.