An implantable system for treating a heart contains a processor, a memory unit, a treatment unit including a treatment electrode, and a detection unit for detecting a cardiac event requiring treatment. The memory unit includes a computer-readable program, which prompts the processor to perform the following steps: a) detecting by way of the detection unit whether a cardiac event to be treated has occurred in the heart; b) if a cardiac event to be treated has occurred, determining a position of the treatment electrode or determining a variable correlating with this position; and c) comparing the position of the treatment electrode or the variable correlating with the position to a reference variable, and carrying out, or not carrying out a cardiac treatment by way of the treatment unit and the treatment electrode as a function of the position of the treatment electrode or the variable correlating with the position.