Neurostimulation with signal duration determined by a cardiac cycle

1. A method of providing an electrical signal to a cranial nerve of a patient for treating a medical condition, comprising:

a) determining a cardiac cycle duration of at least a portion of a cardiac cycle;

b) determining a stimulation duration which is based on a predetermined fraction of the determined cardiac cycle duration, wherein the predetermined fraction is less than one;

c) generating an electrical signal based on the stimulation duration;

d) applying the electrical signal to the cranial nerve for the stimulation duration,

wherein the electrical signal is operative to deliver an electrical signal stimulation to a patient's brain via the cranial nerve; and

e) repeating a-d to automatically adjust the stimulation duration based on changes in the at least a portion of the cardiac cycle.

2. The method of claim 1 wherein at least the portion of the cardiac cycle includes at least one of an R-R interval, a P-P interval, a T-T interval, a P wave interval, a PR segment interval, a PQ segment interval, a QRS interval, an ST segment interval, and an interbeat interval of the patient.

3. The method of claim 2 , wherein the stimulation duration is less than the interbeat interval.

4. The method of claim 3 , wherein the stimulation duration is determined by reference to the interbeat interval based on at least one of the R-R interval immediately preceding a most recently detected R-wave, and a moving average R-R interval calculated over a last n R-R intervals, where n is an integer from 2 to about 10.

5. The method of claim 2 , wherein the stimulation duration is greater than the interbeat interval.

6. The method of claim 1 , wherein the stimulation duration is from 10% of an interbeat interval to 50% of the interbeat interval.

7. The method of claim 1 , wherein applying the electrical signal to the cranial nerve comprises beginning to apply the electrical signal at a particular point in the cardiac cycle of the patient.

8. The method of claim 7 , wherein the particular point in the cardiac cycle is based on at least one of a detected P-wave, a detected Q-wave, a detected R-wave, a detected S-wave, a detected T-wave, and a detected U-wave.

9. The method of claim 7 , wherein the particular point in the cardiac cycle follows a point in the cardiac cycle based on a period which includes a delay period and at least one of a detected P-wave, a detected Q-wave, a detected R-wave, a detected S-wave, a detected T-wave, and a detected U-wave.

10. The method of claim 9 , wherein the delay period is from 0.1 msec to about 1000 msec.

11. The method of claim 1 , wherein applying the electrical signal to the cranial nerve comprises beginning to apply the electrical signal after a selected number of occurrences of at least one of a detected P-wave, a detected Q-wave, a detected R-wave, a detected S-wave, a detected T-wave, and a detected U-wave.

12. The method of claim 11 , wherein applying the electrical signal to the cranial nerve comprises beginning to apply the electrical signal after a predetermined number of R-waves ranging from two R-waves to 1000 R-waves.

13. The method of claim 1 , further comprising:

sensing at least one parameter of the cardiac cycle of the patient based on at least one of a P-wave, a Q-wave, an R-wave, an S-wave, a T-wave, and a U-wave, and

determining the stimulation duration at least partially based on at least one sensed parameter of the cardiac cycle.

14. An implantable medical device (IMD), comprising:

an electrical signal generator; and

a cardiac cycle determination module configured to determine a cardiac cycle duration of at least a portion of a cardiac cycle of a patient; wherein:

the electrical signal generator is configured to provide an electrical signal to a target tissue via a first electrode for a stimulation duration, wherein the stimulation duration is based on a predetermined fraction of a determined cardiac cycle duration, wherein the predetermined fraction is less than one, the stimulation duration being automatically adjusted in response to changes in the at least a portion of the cardiac cycle of the patient; and

wherein the electrical signal is operative to deliver an electrical signal stimulation to a patient's brain.

15. The implantable medical device of claim 14 , wherein the electrical signal is initiated at a time determined by at least one cardiac cycle parameter.

16. The implantable medical device of claim 14 , wherein the stimulation duration is determined by reference to an interbeat interval based on at least one of an R-R interval immediately preceding a most recently detected R-wave, and a moving average R-R interval calculated over a last n R-R intervals, where n is an integer from 2 to about 10.

17. An implantable medical device, comprising:

an electrical signal generator; and

a cardiac cycle determination module adapted to determine a cardiac cycle duration of a patient; and

wherein the electrical signal generator is configured to generate and to deliver at least one electrical signal to a target tissue via a first electrode; and

wherein a stimulation duration of a delivery of the at least one electrical signal is a predetermined fraction of a determined cardiac cycle duration, wherein the predetermined fraction is less than one, the stimulation duration being automatically adjusted in response to changes in a heart parameter of the patient.

18. The implantable medical device of claim 17 , wherein the cardiac cycle duration is an interbeat interval which is based on at least one of a last detected interbeat interval and a moving average interbeat interval calculated over a last n interbeat intervals, where n is an integer from 2 to about 10.

19. The implantable medical device of claim 17 , wherein the predetermined fraction may be automatically adjusted based on a determined condition of the patient.