Patent ID: 8718751

Claim:
A heart monitoring system for monitoring at least a ventricle of a heart, the heart monitoring system comprising: a. a ventricular sensing stage connected or being connectable to an electrode for picking up electric potentials inside at least a ventricle of a heart, the sensing stage sensing an expansion or a contraction of a ventricular myocardium, b. an activity sensor unit determining an activity signal reflecting a patient's physical activity, c. a ventricular impedance or conductance measuring module connected or being connectable to an electrode, the impedance or conductance measuring module including: (1) a current source unit providing a sub-threshold excitation current to the myocardium, and (2) a voltage measurement unit measuring a resulting voltage on the electrode at the myocardium, d. a signal generator module connected to the current source unit and the voltage measurement unit, the signal generator module being configured to construct an intra-cardiac impedance or conductance signal representing impedance and/or conductance: (1) of the myocardium of the heart, and (2) excluding thoracic impedance and/or conductance arising from breathing, e. a filter module filtering the intra-cardiac impedance or conductance signal, f. a memory storing a history of intra-cardiac impedance or conductance signal values, g. a control unit connected to the memory, the ventricular sensing stage, the activity sensor unit and to the ventricular impedance or conductance measuring module, the control unit being configured to: (1) derive an intra-cardiac impedance or conductance change over a preset sample time interval, (2) determine a variability in the intra-cardiac impedance or conductance change over a number of cardiac cycles, (3) compare: (a) the variability in the intra-cardiac impedance or conductance change, and (b) the activity signal, with threshold values and recent values, (4) use the comparison to determine if an episode of sleep disturbed breathing is present, and (5) if sleep disturbed breathing is present, log the sleep disturbed breathing episode in the memory.