The present disclosure provides a strong, flexible catheter shaft for use in a catheter system. The flexible catheter shaft includes a nitinol tube having one or more sets of cuts therein in combination with one or more outer jacket layers. The flexible catheter shaft provides a shaft having sufficient stiffness and kink resistance to allow an operator to advance an electrode basket connected to the flexible catheter shaft through a guide catheter to a target ablation site without causing vessel trauma. The distal tip of the flexible catheter shaft is designed to have sufficient flexibility to reduce any risk of kicking out a guide catheter when tracking the electrode basket around turns in the vasculature of a patient.
