Pulse generation techniques for implantable pulse generator systems
The invention is directed to tri-phasic pulse generation techniques that make use of a pre-stimulus phase, a stimulus phase, and a post-stimulus phase in a pulse generation cycle. During the pre-stimulus phase, an output capacitor is charged to a desired voltage level. During the stimulus phase, the capacitor is discharged, and during the post-stimulus phase recharging of the capacitor begins again. In accordance with the invention, charging of the output capacitor can be terminated during the post-stimulus phase after a measured voltage in the patient is greater than or equal to a threshold.
1. A method of delivering stimulation pulses to patient tissue, the method comprising:
charging a capacitor of an implantable pulse generator system during a pre-stimulus phase;
discharging the capacitor to stimulate patient tissue during a stimulus phase that follows the pre-stimulus phase;
charging the capacitor during a post-stimulus phase that follows the stimulus phase in discrete charging intervals;
taking voltage measurements, during the post-stimulus phase in intervals in which charging does not occur, across the patient tissue where the stimulation pulses are delivered; and
terminating the charging of the capacitor during the post-stimulus phase responsive to the measured voltage across the patient tissue being greater than or equal to a threshold.
2. The method of claim 1 , further comprising measuring the voltage during the post-stimulus phase between the discrete charging intervals of the post-stimulus phase.
3. The method of claim 2 , wherein discharging the capacitor to stimulate the patient tissue comprises stimulating the patient's heart and wherein measuring the voltage across the patient comprises measuring a voltage between two locations on of the patient's heart.
4. The method of claim 1 , wherein the threshold defines a zero voltage value.
5. The method of claim 1 , further comprising:
blanking sensing capabilities of the implantable pulse generator system prior to the pre-stimulus phase; and
terminating the blanking after the measured voltage in the patient is greater than or equal to the threshold.
6. The method of claim 5 , further comprising sensing an evoked response following terminating the blanking of the implantable pulse generator system.
7. The method of claim 5 , wherein terminating the blanking of the implantable pulse generator system occurs within 50 milliseconds after discharging the capacitor to stimulate the patient.
8. The method of claim 1 , wherein the implantable pulse generator system comprises a cardiac pacemaker.
9. An implantable pulse generator, comprising:
a capacitor;
circuitry charging the capacitor during a pre-stimulus phase;
circuitry discharging the capacitor to stimulate patient tissue during a stimulus phase that follows the pre-stimulus phase;
circuitry re-charging the capacitor during a post-stimulus phase that follows the stimulus phase in discrete charging intervals;
circuitry measuring a voltage across the patient tissue during the post-stimulus phase in intervals in which charging does not occur; and
circuitry terminating the charging of the capacitor during the post-stimulus phase responsive to the measured voltage across the patient tissue, which measurement is taken during the post-stimulus phase, being greater than or equal to the threshold.
10. The implantable pulse generator of claim 9 , wherein the threshold defines a zero voltage value.
11. The implantable pulse generator of claim 9 wherein the circuitry measuring the voltage across the patient tissue is specifically invoked during intervals between the discrete charging intervals.
12. An apparatus comprising:
means for charging a capacitor of an implantable pulse generator system during a pre-stimulus phase;
means for discharging the capacitor to stimulate patient tissue during a stimulus phase that follows the pre-stimulus phase;
means for re-charging the capacitor during a post-stimulus phase that follows the stimulus phase in discrete charging intervals;
means for measuring a voltage across the patient tissue during the post-stimulus phase in intervals in which charging does not occur; and
means for terminating the charging of the capacitor during the post-stimulus phase when a measured voltage across the patient tissue, taken during the post-stimulus phase, is greater than or equal to a threshold.
13. The apparatus of claim 12 , further comprising means for measuring the voltage across the patient tissue during the post-stimulus phase between the discrete charging intervals.
14. The apparatus of claim 12 , further comprising:
means for blanking the implantable pulse generator system prior to the pre-stimulus phase; and
means for terminating blanking of the implantable pulse generator system after the measured voltage in the patient is greater than or equal to the threshold.
15. The apparatus of claim 14 , further comprising means for sensing an evoked response following terminating blanking of the implantable pulse generator system.