“…However, to our best knowledge, if the matrix (a i,j ) 1≤i,j≤2 formed by the parameters a 1,1 , a 2,2 describing the self diffusion of the state variables and a 1,2 , a 2,1 describing the influence of each component on another, is diagonalizable then the transformed system satisfies a weakly coupled system. In this case, Carleman estimate is obtained similarly to that of the weakly coupled system, see [8,21,50]. But due to the fact that the anisotropy in the bidomain equations depends on the fiber directions, and the fact that the fiber direction are space dependent, one cannot diagonalize the problem as in [8,50].…”