An apparatus for terminating or unpinning rotating electric activity in a cardiac tissue, the apparatus comprising: - an electric state sensor configured to sense at least one electric parameter of the cardiac tissue; - an electric state analyzer connected to the electric state sensor and configured to analyze the at least one electric parameter sensed by the electric state sensor for rotating electric activity in the cardiac tissue; - a pulse generator connected to the electric state analyzer and configured to generate electric pulses in response to the electric state analyzer analyzing that there is rotating electric activity in the cardiac tissue, the electric pulses including a rotating electric activity termination or unpinning pulse; and - a pulse applicator connected to the pulse generator and configured to apply the electric pulses as electric field pulses extending across the cardiac tissue; characterized in - that the electric pulses include a plurality of rotating electric activity synchronization pulses preceding the rotating electric activity termination or unpinning pulse, - wherein the rotating electric activity synchronization pulses are arranged at first intervals (Tsync), and the rotating electric activity termination or unpinning pulse is arranged at a second interval (Δt) in a range from 0.7 to 1.2 times one of the first intervals (Tsync) after the last one of the plurality of rotating electric activity synchronization pulses, and - wherein at least one of - a first maximum electric field strength (FSsync) as caused by each of the rotating electric activity synchronization pulses is not more than 82 % of a second maximum electric field strength (FStou) as caused by the rotating electric activity termination or unpinning pulse, and - a first electric pulse energy (PEsync) delivered to the cardiac tissue by each of the rotating electric activity synchronization pulses not more than 67 % of a second electric pulse energy (PEtou) delivered to the cardiac tissue by the rotating electric activity termination or unpinning pulse. - an electric state sensor configured to sense at least one electric parameter of the cardiac tissue; - an electric state analyzer connected to the electric state sensor and configured to analyze the at least one electric parameter sensed by the electric state sensor for rotating electric activity in the cardiac tissue; - a pulse generator connected to the electric state analyzer and configured to generate electric pulses in response to the electric state analyzer analyzing that there is rotating electric activity in the cardiac tissue, the electric pulses including a rotating electric activity termination or unpinning pulse; and - a pulse applicator connected to the pulse generator and configured to apply the electric pulses as electric field pulses extending across the cardiac tissue; - that the electric pulses include a plurality of rotating electric activity synchronization pulses preceding the rotating electric activity termination or unpinning pulse, - wherein the rotating electric activity synchronization pulses are arranged at first intervals (Tsync), and the rotating electric activity termination or unpinning pulse is arranged at a second interval (Δt) in a range from 0.7 to 1.2 times one of the first intervals (Tsync) after the last one of the plurality of rotating electric activity synchronization pulses, and - wherein at least one of - a first maximum electric field strength (FSsync) as caused by each of the rotating electric activity synchronization pulses is not more than 82 % of a second maximum electric field strength (FStou) as caused by the rotating electric activity termination or unpinning pulse, and - a first electric pulse energy (PEsync) delivered to the cardiac tissue by each of the rotating electric activity synchronization pulses not more than 67 % of a second electric pulse energy (PEtou) delivered to the cardiac tissue by the rotating electric activity termination or unpinning pulse. - a first maximum electric field strength (FSsync) as caused by each of the rotating electric activity synchronization pulses is not more than 82 % of a second maximum electric field strength (FStou) as caused by the rotating electric activity termination or unpinning pulse, and - a first electric pulse energy (PEsync) delivered to the cardiac tissue by each of the rotating electric activity synchronization pulses not more than 67 % of a second electric pulse energy (PEtou) delivered to the cardiac tissue by the rotating electric activity termination or unpinning pulse.