  We consider the Heisenberg spin chain in the presence of integrable spin
defects. Using the Bethe ansatz methodology, we extract the associated
transmission amplitudes, that describe the interaction between the
particle-like excitations displayed by the models and the spin impurity. In the
attractive regime of the XXZ model, we also derive the breather's transmission
amplitude. We compare our findings with earlier relevant results in the context
of the sine-Gordon model.
