Biventricular cardiac stimulator

1. An implantable cardiac stimulator ( 10 ), comprising

at least one right ventricular sensing unit ( 58 ) which has a first input that is configured to be connected to a right ventricular electrode line ( 16 ) and is configured to analyze a first electric input signal applied to the first input, such that the at least one right ventricular sensing unit detects at least one first signal feature typical of a contraction of a right ventricle and generates a corresponding first output signal;

at least one right ventricular stimulation unit ( 56 ) which has a first output that is configured to be connected to the right ventricular electrode line ( 16 ) and is configured to generate a right ventricular stimulation pulse in response to a first control signal and deliver the right ventricular stimulation pulse via the first output;

at least one left ventricular sensing unit ( 66 ) which has a second input that is configured to be connected to a left ventricular electrode line ( 30 ) and and is configured to analyze a second electric input signal applied to the second input, such that the at least one left ventricular sensing unit detects at least one second signal feature typical of a contraction of a left ventricle and generates a corresponding second output signal;

at least one left ventricular stimulation unit ( 64 ), which has second output that is configured to be connected to the left ventricular electrode line ( 30 ) and is configured to generate a left ventricular stimulation pulse in response to a second control signal and deliver the left ventricular stimulation pulse via the second output;

a stimulation control unit ( 54 ) which is connected to the at least one right ventricular sensing unit ( 58 ), the at least one left ventricular sensing unit ( 66 ), the at least one right ventricular stimulation unit ( 56 ) and the at least one left ventricular stimulation unit ( 64 ) and is configured to process the first and second output signals of the at least one right ventricular sensing unit ( 58 ) and at least one left ventricular sensing unit ( 66 ) and to generate the first and second control signals for the at least one right ventricular stimulation unit ( 56 ) and the at least one left ventricular stimulation unit ( 64 ) to generate near field stimulation pulses sufficient to excite myocardium proximal to a distal end of said right ventricular electrode line and said left ventricular electrode line respectively; and,

wherein the stimulation control unit ( 54 ) is configured to switch a mode of operation between at least one right ventricular stimulation mode configured to generate near field stimulation pulses

in which no control signals to trigger left ventricular pulses are output to the at least one left ventricular stimulation unit, and

a biventricular stimulation mode alternately, configured to generate near field stimulation pulses;

wherein the stimulation control unit is additionally configured to switch the mode of operation as a function of a signal that indicates a duration of a prevailing QRS signal interval of a certain signal or any of the first and second electric input signals, such that the stimulation control unit switches to

the biventricular stimulation mode configured to generate near field stimulation pulses only when a comparison of the signal that indicates the duration of the prevailing QRS signal interval with a first comparison value reveals that the duration of the prevailing QRS signal interval is longer than a first reference value represented by the first comparison value for a predefined plurality number of cardiac cycles in a row, and switches to

the at least one right ventricular stimulation mode configured to generate near field stimulation pulses only when the comparison of the signal that indicates the duration of the prevailing QRS signal interval with a second comparison value reveals that the duration of the prevailing QRS signal interval is shorter than a second reference value represented by the second comparison value for a predefined plurality number of cardiac cycles in a row and, wherein the near field stimulation stimulates only the myocardial cells in an immediate vicinity of the stimulation pulses.

2. The implantable cardiac stimulator according to claim 1 , wherein the first and second comparison values and the first and second reference values are each identical.

3. The implantable cardiac stimulator according to claim 1 , wherein the stimulation control unit ( 54 ) is configured to determine the signal that indicates a duration of a QRS signal interval, so that the signal that indicates the duration of the QRS signal interval reflects an interval of time between the contraction of the right ventricle detected by the at least one right ventricular sensing unit ( 58 ) and the contraction of the left ventricle that is to be causally assigned to a right ventricular contraction detected by the at least one left ventricular sensing unit ( 66 ).

4. The implantable cardiac stimulator according to claim 1 , further comprising:

a right atrial sensing unit ( 62 ) which has a third input that is configured to be connected to a right atrial electrode line ( 14 ) and is configured to analyze a third electric input signal applied to the third input, such that the right atrial sensing unit ( 62 ) detects at least one third signal feature typical of a contraction of a right atrium and generates a corresponding third output signal; and,

wherein the stimulation control unit ( 54 ) is configured to determine the signal which indicates a duration of a QRS signal interval wherein the signal reflects an interval of time between the contraction of the right atrium detected by the right atrial sensing unit ( 62 ) and the contraction of the right ventricle to be assigned causally to a right atrial contraction detected by the at least one right ventricular sensing unit ( 58 ).

5. The implantable cardiac stimulator according to claim 1 , further comprising:

a right atrial sensing unit ( 62 ) which has a third input that is configured to be connected to a right atrial electrode line ( 14 ) and is configured to analyze a third electric input signal applied to the third input, such that the right atrial sensing unit ( 62 ) detects at least one third signal feature typical of a contraction of a right atrium and generates a corresponding third output signal; and,

wherein the stimulation control unit ( 54 ) is configured to determine the signal which indicates a duration of a QRS signal interval wherein the signal reflects an interval of time between a contraction of the right atrium detected by the right atrial sensing unit ( 62 ) and the contraction of the left ventricle to be assigned causally to a right atrial contraction detected by the at least one left ventricular sensing unit ( 66 ).

6. The implantable cardiac stimulator according to claim 1 , wherein the stimulation control unit ( 54 ) is configured to suppress a delivery of right ventricular stimulation pulses in the at least one right ventricular stimulation mode.

7. The implantable cardiac stimulator according to claim 1 , wherein the stimulation control unit ( 54 ) is configured to switch from one stimulation mode to another after each time a measured value exceeds or drops below a respective comparison value.

8. The implantable cardiac stimulator according to claim 1 , wherein the stimulation control unit ( 54 ) is configured to switch from one stimulation mode to another only when the signal that indicates a duration of a QRS signal interval has exceeded or dropped below a respective comparison value for a predetermined number of cardiac cycles.

9. The implantable cardiac stimulator according to claim 1 , wherein the stimulation control unit ( 54 ) is configured to detect an interval comprising a respective intrinsic VV interval in a biventricular CRT stimulation mode, wherein said interval reflects an interval of time between the contraction of the right ventricle detected by the at least one right ventricular sensing unit ( 58 ) and a contraction of the left ventricle to be causally assigned to a right ventricular contraction detected by the at least one left ventricular sensing unit ( 66 ), and to determine a left ventricular stimulation point in time that occurs after the end of the respective intrinsic VV interval thereby determined.

10. The implantable cardiac stimulator according to claim 1 , wherein the stimulation control unit ( 54 ) is connected to a memory unit ( 80 ) and is configured to store points in time of the respective switching to switch between stimulation modes in the memory unit ( 80 ).

11. The implantable cardiac stimulator according to claim 10 , wherein the memory unit ( 80 ) is connected to a telemetry unit ( 82 ) which is configured to transmit wirelessly data stored in the memory unit ( 80 ).

12. The implantable cardiac stimulator according to claim 1 , wherein the stimulation control unit is additionally configured to switch the mode of operation as a function of mitral reflux or measured ejection fraction or both said mitral reflux and said measured ejection fraction alone or in combination with said duration of said prevailing QRS signal interval.

13. The implantable cardiac stimulator according to claim 1 , further comprising a timer, and wherein the stimulation control unit comprises an intrinsic VV interval conduction time measuring unit, an intrinsic VV interval comparison unit and a stimulation mode switch, such that the intrinsic VV interval conduction time measuring unit is configured to cooperate with the timer to determine an intrinsic VV interval conduction time in a biventricular CRT stimulation mode.

14. The implantable cardiac stimulator according to claim 13 , wherein said intrinsic VV interval reflects an interval of time between the contraction of the right ventricle detected by the at least one right ventricular sensing unit ( 58 ) and a contraction of the left ventricle to be causally assigned to a right ventricular contraction detected by the at least one left ventricular sensing unit ( 66 ), and to determine a left ventricular stimulation point in time that occurs after the end of the respective intrinsic VV interval thereby determined and, wherein the near field stimulation stimulates only the myocardial cells in an immediate vicinity of the stimulation pulses.

15. An implantable cardiac stimulator ( 10 ), comprising

at least one right ventricular sensing unit ( 58 ) which has a first input that is configured to be connected to a right ventricular electrode line ( 16 ) and is configured to analyze a first electric input signal applied to the first input, such that the at least one right ventricular sensing unit detects at least one first signal feature typical of a contraction of a right ventricle and generates a corresponding first output signal;

at least one right ventricular stimulation unit ( 56 ) which has a first output that is configured to be connected to the right ventricular electrode line ( 16 ) and is configured to generate a right ventricular stimulation pulse in response to a first control signal and deliver the right ventricular stimulation pulse via the first output;

at least one left ventricular sensing unit ( 66 ) which has a second input that is configured to be connected to a left ventricular electrode line ( 30 ) and and is configured to analyze a second electric input signal applied to the second input, such that the at least one left ventricular sensing unit detects at least one second signal feature typical of a contraction of a left ventricle and generates a corresponding second output signal;

at least one left ventricular stimulation unit ( 64 ), which has second output that is configured to be connected to the left ventricular electrode line ( 30 ) and is configured to generate a left ventricular stimulation pulse in response to a second control signal and deliver the left ventricular stimulation pulse via the second output;

a stimulation control unit ( 54 ) which is connected to the at least one right ventricular sensing unit ( 58 ), the at least one left ventricular sensing unit ( 66 ), the at least one right ventricular stimulation unit ( 56 ) and the at least one left ventricular stimulation unit ( 64 ) and is configured to process the first and second output signals of the at least one right ventricular sensing unit ( 58 ) and at least one left ventricular sensing unit ( 66 ) and to generate the first and second control signals for the at least one right ventricular stimulation unit ( 56 ) and the at least one left ventricular stimulation unit ( 64 ) to generate near field stimulation pulses sufficient to excite myocardium proximal to a distal end of said right ventricular electrode line and said left ventricular electrode line respectively; and,

wherein the stimulation control unit ( 54 ) is configured to switch a mode of operation between at least one right ventricular stimulation mode configured to generate near field stimulation pulses

in which no control signals to trigger left ventricular pulses are output to the at least one left ventricular stimulation unit, and

a biventricular stimulation mode alternately, configured to generate near field stimulation pulses;

wherein the stimulation control unit is additionally configured to switch the mode of operation as a function of a signal that indicates a duration of a prevailing QRS signal interval of a certain signal or any of the first and second electric input signals, such that the stimulation control unit switches to

the biventricular stimulation mode configured to generate near field stimulation pulses only when a comparison of the signal that indicates the duration of the prevailing QRS signal interval with a first comparison value reveals that the duration of the prevailing QRS signal interval is longer than a first reference value represented by the first comparison value for a predefined plurality number of cardiac cycles in a row,

and switches to

the at least one right ventricular stimulation mode configured to generate near field stimulation pulses only when the comparison of the signal that indicates the duration of the prevailing QRS signal interval with a second comparison value reveals that the duration of the prevailing QRS signal interval is shorter than a second reference value represented by the second comparison value for a predefined plurality number of cardiac cycles in a row;

a timer coupled with said stimulation control unit;

wherein the stimulation control unit comprises an intrinsic VV interval conduction time measuring unit, an intrinsic VV interval comparison unit and a stimulation mode switch;

such that the intrinsic VV interval conduction time measuring unit is configured to cooperate with the timer to

determine an intrinsic VV interval conduction time in a biventricular CRT stimulation mode, wherein said intrinsic VV interval reflects an interval of time between the contraction of the right ventricle detected by the at least one right ventricular sensing unit ( 58 ) and a contraction of the left ventricle to be causally assigned to a right ventricular contraction detected by the at least one left ventricular sensing unit ( 66 ), and

determine a left ventricular stimulation point in time that occurs after the end of the respective intrinsic VV interval thereby determined.