Apparatus for spatially and temporally distributing cardiac electrical stimulation
View Patent ↗A cardiac electro-stimulatory device and method for operating same in which stimulation pulses are distributed among a plurality of electrodes fixed at different sites of the myocardium in order to reduce myocardial hypertrophy brought about by repeated pacing at a single site and/or increase myocardial contractility. In order to spatially and temporally distribute the stimulation, the pulses are delivered through a switchable pulse output configuration during a single cardiac cycle, with each configuration comprising one or more electrodes fixed to different sites in the myocardium.
1. Apparatus for cardiac therapy, the apparatus comprising:
a plurality of electrodes adapted for fixation to a heart chamber;
a control unit comprising pulse generating circuitry operable in a plurality of defined pulse output configurations, wherein each pulse output configuration activates a subset of the plurality of the electrodes, the circuitry adapted for outputting:
a first pulse type comprising pulses to provide cardiac contractility modulating non-excitatory stimulation pulses to a selected one of the plurality of pulse output configurations in order to stimulate the heart chamber during a refractory period, wherein the pulse generating circuitry is capable of separately generating pulses to one or more of a plurality of electrodes; and
a second pulse type comprising a defibrillation signal; and
a switching module adapted to switch the control unit between outputting different pulse types, wherein the switching module is responsive to a sensed time delay of a depolarization occurring in at least a portion of the heart.
2. Apparatus according to claim 1 , wherein the pulse generating circuitry is further adapted for outputting a third pulse type comprising a pacing signal.
3. Apparatus according to claim 2 , comprising at least one thoracic sensor adapted to provide an output signal related to a cardiac output parameter;
wherein the switching module is responsive to said output signal.
4. Apparatus according to claim 3 , wherein the sensor measures a mean or a minimum heart rate over a time interval and the switching module is adapted to respond to the mean or the minimum heart rate measured over a time interval.
5. Apparatus according to claim 1 , comprising at least one thoracic sensor adapted to provide an output signal related to a cardiac output parameter;
wherein the switching module is responsive to said output signal.
6. Apparatus according to claim 5 , wherein the at least one thoracic sensor senses intra-thoracic impedance.
7. Apparatus according to claim 5 , wherein the thoracic sensor comprises a respiration rate detector and the switching module is responsive to the respiration rate.
8. Apparatus according to claim 5 , wherein the thoracic sensor is adapted to sense a condition correlative to edema and the switching module is responsive to the condition correlative to edema.
9. Apparatus according to claim 8 , wherein the thoracic sensor is adapted to sense a change in a baseline thoracic impedance associated with fluid buildup in a portion of a thorax of a subject.
10. Apparatus according to claim 9 , wherein the change in the baseline thoracic impedance comprises a decrease.
11. Apparatus according to claim 9 , in which the baseline portion of the thoracic impedance is less than or equal to a cutoff frequency value that is between 0.01 Hz and 0.5 Hz inclusive.
12. Apparatus according to claim 11 , in which the cutoff frequency value is approximately 0.1 Hz.
13. Apparatus according to claim 1 , wherein the switching module operates according to a switching algorithm.
14. Apparatus according to claim 13 , wherein the switching algorithm switches the control unit intermittently.
15. Apparatus according to claim 13 , wherein the switching algorithm switches the control unit substantially on a beat-to-beat basis.
16. Apparatus according to claim 13 , wherein the switching algorithm switches the control unit at a specified time interval.
17. Apparatus according to claim 13 , wherein the switching algorithm switches the control unit after a specified number of heart beats.
18. Apparatus according to claim 1 , wherein the switching module initiates or adjusts a cardiac management therapy.
19. Apparatus according to claim 18 , in which the cardiac management therapy comprises a cardiac resynchronization therapy that coordinates a spatial nature of a depolarization associated with a heart contraction in at least one heart chamber.
20. Apparatus according to claim 18 , in which the cardiac management therapy comprises delivering the pulses of non-excitatory electrical energy to a portion of a heart during a refractory time period of the portion of the heart.