A catheter device (20, 60a, 60b, 90) for ablating biological material is described. The catheter device comprises (a) a longitudinal structure (62, 63, 65)； (b) an applicator (53, 61, 66) for ablating the biological material, wherein the applicator is installed at the longitudinal structure； (c) a first electrode (23, 23a, 23i) being attached to the longitudinal structure； (d) a second electrode (46, 46a, 46b) being attached to the longitudinal structure； (e) an interface (47a, 47b, 48, 49) being connected directly or indirectly to the longitudinal structure； (f) a first lead (22, 22a, 221) electrically connecting the first electrode with the interface； and (g) a second lead (45a, 45b) electrically connecting the second electrode with the interface. The interface is configured for electrically connecting the first lead and the second lead with a measurement device for electrically stimulating the first electrode and the second electrode and for detecting an electric quantity being associated with an electric response of an biological material being located in between the two stimulated electrodes. Further, a catheter system with such a catheter device is described.
