Cardiac stimulating device

An implantable cardiac stimulating device (1), comprising:

• a housing (2), a pacing circuit (3) and leads (17, 18, 19, 20,)
• said pacing circuit (3) comprising a control circuit (4) and stimulating output means (10, 13, 15) and amplifying and sensing means (11, 12, 14, 16) for sensing cardiac depolarizations, said pacing circuit (3) being adapted to be connected to a first electrode (23) to be positioned to stimulate and sense depolarizations in the left ventricle (9) of the heart (5), said pacing circuit being adapted to to be connected to a second electrode (22) to be positioned to sense depolarisations of the left atrium, said pacing circuit being adapted to be connected to a third electrode (21) to be positioned in the right atrium (6) adapted to stimulate and sense depolarisations, characterized in that a sensed depolarization of the right atrium (6) starts a first AV-delay, AV1, said first AV-delay being superseded by a second AV-delay, AV2, optimized for the left side of the heart upon the sensing of a left atrial depolarization by the left atrial detection means (12).