Implantable leadless pacemaker with atrial-ventricular synchronized pacing

An implantable leadless pacemaker (iLP) for a human or animal heart, the iLP comprising:

• a housing;
• at least two electrode poles for picking up electrical potentials and/or delivering electrical stimulation;
• a stimulation control unit in connection with the electrode poles;
• a sensing unit in connection with at least one electrode pole;
• and
• a signal processing and signal evaluation unit in connection with the sensing unit;
• wherein the iLP is configured to be anchored within a ventricle,
• wherein the sensing unit is configured to sense electrical potentials via the at least two electrode poles,
• wherein the sensing unit is configured to sense a first signal associated with an activity of the ventricle, the first signal comprising a QRS-complex,
• wherein the stimulation control unit is configured to deliver electrical stimulation in the ventricle via the at least two electrode poles,
• wherein the sensing unit is configured to sense a second signal,
• wherein the sensing unit comprises an impedance sensor which is configured to acquire impedance signals representing cardiac activity,
• wherein the second signal is an impedance signal representing contraction of an atrium,
• wherein the sensing unit is configured to sense the QRS-complex, wherein upon sensing the QRS-complex, the signal processing and signal evaluation unit is configured to begin a timer in which no atrial activity should be detected, and wherein at the end of the timer, the signal processing and signal evaluation unit is configured to enter a detection phase in which the contraction of the atrium is expected.