An implantable cardiac device includes a housing (2), pulse generator (7) therein to generate physiologically effective electrical pulses, a shock lead (3), externally of the housing (2), connectable to the pulse generator (7) and implantable into a patient's body to apply physiologically effective electrical pulses to the patient's body, a monitor (8) to automatically detect a lead condition as to whether the shock lead (3) is implanted or not, and control (9), which due to the detected lead condition automatically enables or disables the pulse generator (7).