Not to mention that the human heart has a finite number of cells. The amount of "memory" (or whatever word you use for the heat) is finite, making it a DFA/FSM not a Turing machine.
You could argue that the number of cells is so huge that we might as well treat it like a Turing Machine, but given that the researchers were simulating the human heart, I'd disagree with that.
Knowing that the human heart weights on average 300g, it makes about 10^(10(+/-0.5)) cells, hence 2^(10^10) states for a FSM built on it (rough approximation).
Even though the simulated experiment had obviosuly less cells, I think that the real heart can in practice be considered as turing equivalent.
You could argue that the number of cells is so huge that we might as well treat it like a Turing Machine, but given that the researchers were simulating the human heart, I'd disagree with that.