Implantable medical device fixation

1. An assembly comprising:

an implantable medical device comprising:

a plurality of electrodes; and

circuitry configured to deliver cardiac pacing stimulation via the plurality of electrodes; and

a set of active fixation tines,

wherein each active fixation tine of the set of active fixation tines is deployable from a spring-loaded position to a hooked position by at least being released from the spring-loaded position,

wherein each active fixation tine of the set of active fixation tines is fixedly attached to the implantable medical device in both the spring-loaded position and the hooked position, and

wherein the active fixation tines are configured to create forces when deployed such that the active fixation tines are configured to pull the implantable medical device towards patient tissue as the active fixation tines penetrate the patient tissue.

2. The assembly of claim 1 , wherein distal ends of the active fixation tines point distally away from the implantable medical device in the spring-loaded position.

3. The assembly of claim 1 , wherein the active fixation tines are positioned substantially equidistant from each other in a circular arrangement.

4. The assembly of claim 3 , wherein the active fixation tines are oriented outwardly relative to the circular arrangement.

5. The assembly of claim 3 , wherein at least one electrode of the plurality of electrodes is located within the circular arrangement, wherein the implantable medical device is configured such that the electrode contacts the patient tissue when the implantable medical device is secured to the patient tissue by the set of active fixation tines.

6. The assembly of claim 5 , wherein the active fixation tines are configured to press the at least one electrode on the patient tissue.

7. The assembly of claim 5 , wherein the set of fixation tines extend from the implantable medical device at a longitudinal position that is proximal to the at least one electrode within the circular arrangement.

8. The assembly of claim 1 , wherein each active fixation tine of the set of active fixations tines comprises a super-elastic material.

9. The assembly of claim 1 , wherein a portion of each fixation tine extends distally from a distal end of the implantable medical device in both the spring-loaded position and the hooked position.

10. The assembly of claim 1 , wherein each active fixation tine of the set of active fixations tines is configured to have a column strength sufficient to enable a distal end of the tine to penetrate cardiac tissue during deployment.

11. The assembly of claim 10 , wherein the cardiac tissue comprises endocardial tissue, and the column strength is insufficient to penetrate epicardial tissue.

12. The assembly of claim 1 , wherein the implantable medical device defines a longitudinal axis, wherein each fixation tine of the set of fixation tines includes at least a first portion that extends from the implantable medical device and a second portion that extends from the first portion, and wherein in the spring-loaded position the first portion extends distally beyond a distal end of the implantable medical device and toward the longitudinal axis and the second portion extends distally from the first portion and away from the longitudinal axis.

13. The assembly of claim 12 , wherein in the hooked position the first portion extends distally from the distal end of the implantable medical device the second portion is bent back proximally.

14. The assembly of claim 12 , wherein the second portion and the first portion define an arcuate shape in the spring-loaded position.

15. The assembly of claim 1 , wherein the implantable medical device is a leadless pacemaker.

16. A kit comprising:

an assembly comprising an implantable medical device and a set of active fixation tines, the implantable medical device comprising:

a plurality of electrodes; and

circuitry configured to deliver cardiac pacing stimulation via the plurality of electrodes,

wherein each active fixation tine of the set of active fixation tines is deployable from a spring-loaded position to a hooked position by at least being released from the spring-loaded position,

wherein each active fixation tine of the set of active fixation tines is fixedly attached to the implantable medical device in both the spring-loaded position and the hooked position, and

wherein the active fixation tines are configured to create forces when deployed such that the active fixation tines are configured to pull the implantable medical device towards patient tissue as the active fixation tines penetrate the patient tissue; and

a catheter forming a lumen sized to receive the implantable medical device and hold the active fixation tines in the spring-loaded position, wherein the lumen includes an aperture that is adjacent to a distal end of the catheter; and

a deployment element configured to initiate deployment of the active fixation tines while the implantable medical device is positioned within the lumen of the catheter.

17. The kit of claim 16 , wherein the deployment element is configured to push the implantable medical device towards the distal end of the catheter until distal ends of the active fixation tines extend out of the aperture.

18. The kit of claim 16 , wherein the implantable medical device is a leadless pacemaker.

19. The kit of claim 16 , wherein the set of active fixation tines are formed from a shape memory alloy material.

20. The kit of claim 16 , further comprising a tether attached to the implantable medical device, the tether being configured to facilitate pulling the implantable medical device back into the lumen from a proximal end of the catheter after the active fixation tines are deployed, wherein pulling the implantable medical device back into the lumen with the tether returns the active fixation tines to the spring-loaded position from the hooked position such that the active fixation tines can be redeployed with the deployment element.