We use the inelastic thermal spike model for insulators and molecular dynamic simulations to investigate the effects of pre-existing damage on the energy dissipation and structural alterations in KTaO3 under irradiation with 21 MeV Ni ions. Our results reveal a synergy between the pre-existing defects and the electronic energy loss, indicating that the defects play an important role on the energy deposition in the system. Our findings highlight the need for better understanding on the role of defects in electronic energy dissipation and the coupling of the electronic and atomic subsystems.