Neurostimulation in a neural fulcrum zone for the treatment of chronic cardiac dysfunction
Systems and methods are provided for delivering neurostimulation therapies to patients for treating chronic heart failure. A neural fulcrum zone is identified and ongoing neurostimulation therapy is delivered within the neural fulcrum zone. This neural fulcrum zone corresponds to a combination of stimulation parameters at which autonomic engagement is achieved, while the tachycardia-inducing stimulation effects are offset by the bradycardia-inducing effects, thereby minimizing side effects such as significant heart rate changes while providing a therapeutic level of stimulation.
1. A method of operating an implantable medical device (IMD), the method comprising:
generating a plurality of stimulation signals configured to stimulate a nerve of a patient, each stimulation signal of the plurality of stimulation signals having a duty cycle, a frequency, an amplitude, and a pulse width, wherein generating the plurality of stimulation signals comprises adjusting at least one of the duty cycle, the amplitude, or the pulse width while maintaining a fixed frequency across the plurality of stimulation signals;
detecting a cardiac parameter response of the patient during the generation of the plurality of stimulation signals;
identifying a range of the adjusted at least one of the duty cycle, the pulse width, or the amplitude that results in the cardiac parameter response being between a baseline cardiac parameter and a cardiac parameter decrease threshold; and
delivering a plurality of stimulation signals at a duty cycle, a frequency, an amplitude, and a pulse width resulting in the cardiac parameter response being between the baseline cardiac parameter and the cardiac parameter decrease threshold.
2. The method of claim 1 , wherein the fixed frequency is selected from 2 Hz to 20 Hz.
3. The method of claim 2 , wherein the fixed frequency is 5 Hz.
4. The method of claim 1 , wherein the amplitude is adjusted between at least a subset of 0 mA to 3.5 mA.
5. The method of claim 1 , wherein the amplitude is adjusted while maintaining a fixed pulse width and the fixed frequency.
6. The method of claim 5 , wherein the fixed pulse width is 250 μs.
7. The method of claim 1 , wherein generating the plurality of stimulation signals further comprises generating stimulation signals having the fixed frequency, an amplitude of 1.0 mA, and a pulse width of 250 μs and increasing the at least one of the amplitude or pulse width while maintaining the fixed frequency.
8. The method of claim 7 , wherein the fixed frequency is selected from 2 Hz to 20 Hz.
9. The method of claim 1 , wherein the cardiac parameter response is a heart rate response of the patient.
10. The method of claim 1 , further comprising:
increasing the at least one of the duty cycle, the pulse width, or the amplitude in response to detecting a tachycardia condition, wherein the tachycardia condition is defined by a cardiac parameter increase above the baseline cardiac parameter; and
decreasing the at least one of the duty cycle, the pulse width, or the amplitude in response to detecting a bradycardia condition, wherein the bradycardia condition is defined by a heart rate decrease below the heart rate decrease threshold.
11. An implantable medical device (IMD), comprising:
a neurostimulator configured to deliver a stimulation signal to a nerve of a patient; and
a control system programmed to:
generate a plurality of stimulation signals configured to stimulate a nerve of a patient, each stimulation signal of the plurality of stimulation signals having a duty cycle, a frequency, an amplitude, and a pulse width, wherein generating the plurality of stimulation signals comprises adjusting at least one of the duty cycle, the amplitude, or the pulse width while maintaining a fixed frequency across the plurality of stimulation signals;
detect a cardiac parameter response of the patient during the generation of the plurality of stimulation signals;
identify a range of the adjusted at least one of the duty cycle, the pulse width, or the amplitude that results in the cardiac parameter response being between a baseline cardiac parameter and a cardiac parameter decrease threshold; and
deliver a plurality of stimulation signals at a duty cycle, a frequency, an amplitude, and a pulse width resulting in the cardiac parameter response being between the baseline cardiac parameter and the cardiac parameter decrease threshold.
12. The IMD of claim 11 , wherein the fixed frequency is selected from 2 Hz to 20 Hz.
13. The IMD of claim 12 , wherein the fixed frequency is 5 Hz.
14. The IMD of claim 11 , wherein the amplitude is adjusted between at least a subset of 0 mA to 3.5 mA.
15. The IMD of claim 11 , wherein the control system is configured to adjust the amplitude while maintaining a fixed pulse width and the fixed frequency.
16. The IMD of claim 15 , wherein the fixed pulse width is 250 μs.
17. The IMD of claim 11 , wherein the control system is further configured to generate the plurality of stimulation signals by generating stimulation signals having the fixed frequency, an amplitude of 1.0 mA, and a pulse width of 250 μs and increasing the at least one of the amplitude or pulse width while maintaining the fixed frequency.
18. The IMD of claim 17 , wherein the fixed frequency is selected from 2 Hz to 20 Hz.
19. The IMD of claim 11 , wherein the cardiac parameter response is a heart rate response of the patient.
20. The IMD of claim 11 , wherein the control system is further configured to:
increase the at least one of the duty cycle, the pulse width, or the amplitude in response to detecting a tachycardia condition, wherein the tachycardia condition is defined by a cardiac parameter increase above the baseline cardiac parameter; and
decrease the at least one of the duty cycle, the pulse width, or the amplitude in response to detecting a bradycardia condition, wherein the bradycardia condition is defined by a cardiac parameter decrease below the cardiac parameter decrease threshold.