A system, comprising: an electrostimulation circuit configured to deliver electrostimulation to one or more sites in at least one chamber of a heart; a sensor circuit including a sense amplifier to sense a physiological signal including during the electrostimulation of the one or more candidate sites; a therapy programmer circuit in communication with the sensor circuit, the therapy programmer circuit configured to: determine, using the sensed physiological signal, a first stimulation vector for electrostimulation at a first left ventricular site, the first stimulation vector including a first LV cathode and a first anode; characterised in that the therapy programmer circuitry is further configured to determine, based on the first stimulation vector, a second stimulation vector for electrostimulation at a different second LV site, the second stimulation vector including a second LV cathode and a second anode; and determine a therapy mode including one or more of a first chronological order or a first timing offset between a first LV stimulation delivered according to the first stimulation vector and a second LV stimulation delivered according to the second stimulation vector; a controller circuit to configure the electrostimulation circuit to deliver the first and second LV stimulations according to the therapy mode. an electrostimulation circuit configured to deliver electrostimulation to one or more sites in at least one chamber of a heart; a sensor circuit including a sense amplifier to sense a physiological signal including during the electrostimulation of the one or more candidate sites; a therapy programmer circuit in communication with the sensor circuit, the therapy programmer circuit configured to: determine, using the sensed physiological signal, a first stimulation vector for electrostimulation at a first left ventricular site, the first stimulation vector including a first LV cathode and a first anode; characterised in that the therapy programmer circuitry is further configured to determine, based on the first stimulation vector, a second stimulation vector for electrostimulation at a different second LV site, the second stimulation vector including a second LV cathode and a second anode; and determine a therapy mode including one or more of a first chronological order or a first timing offset between a first LV stimulation delivered according to the first stimulation vector and a second LV stimulation delivered according to the second stimulation vector; determine, using the sensed physiological signal, a first stimulation vector for electrostimulation at a first left ventricular site, the first stimulation vector including a first LV cathode and a first anode; characterised in that the therapy programmer circuitry is further configured to determine, based on the first stimulation vector, a second stimulation vector for electrostimulation at a different second LV site, the second stimulation vector including a second LV cathode and a second anode; and determine a therapy mode including one or more of a first chronological order or a first timing offset between a first LV stimulation delivered according to the first stimulation vector and a second LV stimulation delivered according to the second stimulation vector; a controller circuit to configure the electrostimulation circuit to deliver the first and second LV stimulations according to the therapy mode.