Data management system for implantable cardiac device

• US 6,526,314 B1
• Filed: 08/24/1999
• Issued: 02/25/2003
• Est. Priority Date: 08/20/1999
• Status: Expired due to Fees

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Gilkerson, James O., Conley, Vickie L., Doshi, Hiten J., Mackey, LeAnne Marie, Eberle, Jason W.
• Primary Examiner(s): Layno, Carl
• Application Number:
  US09/382,034
• Time in Patent Office: 1,281 Days
• Field of Search: 600/509, 600/523, 607/59, 607/9
• US Class Current: 600/523
• CPC Class Codes: A61N 1/3704 Circuits specially adapted therefor, e.g. for sensitivity control

Abstract

A system and method for storing episodic data collected by an implantable medical device. If there are no unallocated storage locations, collected data associated with an episode is stored in locations that are freed from allocations to previous episodes. The least recently allocated of the storage locations allocated to episodes of a lower priority type may be freed first in order to maintain storage of higher priority episodic data. The method and system also allows a specified ratio of stored data allocated to episodes of one priority type to that of another priority type to be maintained.

Claims

1. A system for storing episodic data collected by an implantable medical device, comprising:

a history storage structure comprising an array of nodes and wherein data associated with an episode is stored by allocating a history storage node to the episode;

a linked list of unallocated history storage nodes;

a priority type linked list of history storage nodes for each one of a plurality of types of episodes, wherein episodes are classified as being one of a plurality of priority types going from lower to higher; and

,

wherein a history storage node is allocated to a new episode from the list of unallocated history storage nodes unless the unallocated list is empty, in which case the oldest node from one of the priority type lists is freed for allocation to the new episode.

2. The system of claim 1 wherein history storage nodes are freed from priority type lists and allocated to new episodes according to priority unless a specified maximum number of stored episodes of one particular type would be exceeded by the allocation.

3. The system of claim 1 wherein history storage nodes are freed from lower priority type lists in preference to higher priority type lists in order to allocate a previously allocated node to a new episode.

4. The system of claim 1 further comprising:

a history management structure comprising an array of nodes, wherein for each history storage node allocated to an episode, a history management node is also allocated to the episode and associated with the allocated history storage node;

wherein each allocated history management node has a storage link field that points to the history storage node associated therewith; and

,

wherein the priority type linked lists of history storage nodes are formed by linking associated history management nodes with each allocated history management node having a link field pointing to an adjacent node in a priority type linked list of history management nodes.

5. The system of claim 4 wherein the priority type linked lists are doubly linked lists with each allocated history management node having link fields pointing to adjacent nodes in both directions.

6. The system of claim 5 further comprising a doubly linked list of all allocated history management nodes with each allocated node having link fields pointing to adjacent nodes in both directions in the all allocated node list.

7. The system of claim 6 wherein the nodes of the priority type linked lists and the all allocated linked list are linked sequentially in accordance with when the episodes to which the nodes are allocated occurred.

8. The system of claim 7 further comprising:

a data storage structure comprising an array of nodes, wherein for each history storage and history management node allocated to an episode, a data storage node is also allocated to the episode and associated with the allocated history storage and history management node;

wherein each allocated history storage node has a link field pointing to an associated data storage node; and

,

wherein each data storage node references a data storage block in which episodic data is stored.

9. The system of claim 8 wherein episodic data may be stored in a plurality of data storage blocks referenced by a linked list of data storage nodes allocated to the episode with each allocated data storage node having a link field for pointing to an adjacent data storage node in the linked list.

10. The system of claim 9 wherein the history management structure comprises nodes designated as list heads for the unallocated linked list, the all allocated linked list, and the priority type linked lists.

11. The system of claim 10 wherein each history management node designated as a list head has link fields for pointing to adjacent nodes in both directions.

12. The system of claim 11:

wherein episodic data collected before and after a therapy attempt associated with an episode may be stored in a plurality of data storage blocks referenced by a linked list of data storage nodes allocated to storing data collected before and after the attempt;

wherein a history storage node allocated to an episode has a link field that may reference a history storage node allocated to a therapy attempt associated with the episode; and

,

wherein a history storage node allocated to an attempt has a data field in which is stored a value indicating that the node is allocated to an attempt, a link field that references a data storage node allocated to storing data collected before the therapy attempt, and a link field that references a data storage node allocated to storing data collected after the therapy attempt.

13. The system of claim 12 wherein a history storage node allocated to an attempt has a link field that references history storage nodes allocated to any subsequent attempts.

14. The system of claim 1 wherein cardiac electrogram data collected prior to onset of an episode is stored in one or more data storage blocks referenced by a history storage node allocated to the episode.

15. The system of claim 1 wherein cardiac interval data and electrogram data collected after onset of an episode is stored in one or more data storage blocks referenced by a history storage node allocated to the episode.

16. The system of claim 1 wherein cardiac electrogram data collected after onset of an episode is stored in one or more data storage blocks referenced by a history storage node allocated to the episode.

17. The system of claim 11 wherein cardiac electrogram data collected before and after a therapy attempt associated with an episode is stored in one or more data storage blocks referenced by a history storage node allocated to the episode.

18. The system of claim 11 wherein the priority types of episodes stored include an atrial tachyarrhythmia response, a low priority ventricular tachyarrhythmia response, and a high priority ventricular tachyarrhythmia response.

19. The system of claim 11 wherein when a history storage node allocated to an episode is freed, the history management node allocated to the episode, all history storage nodes allocated to therapy attempts associated with the episode, and all data storage nodes and blocks allocated to the episode or associated attempts are also freed.

20. The system of claim 11 wherein a history storage node is allocated to a new therapy attempt associated with an episode from the list of unallocated history storage nodes unless the unallocated list is empty, in which case the oldest node from one of the priority type lists is freed and added to the unallocated list for allocation to the new episode, and wherein the freed node is taken from a lower priority list in preference to a higher priority list unless a specified maximum number of stored episodes of one particular type would then be exceeded.

21. The system of claim 11 wherein a data storage node and the data storage block referenced thereby are allocated to a present episode from the list of unallocated data storage nodes unless the unallocated list is empty, in which case a data storage node allocated to the oldest episode in one of the priority type lists is freed and added to the unallocated list for allocation to the present episode, and wherein the oldest episode is taken from a lower priority list in preference to a higher priority list.

22. A method for storing episodic data collected by an implantable medical device, comprising:

maintaining a linked list of unallocated data storage nodes, wherein each data storage node references a location for storing collected data;

allocating a data storage node from the unallocated list to each episode for which collected data is to be stored;

maintaining a priority type linked list corresponding to each one of a plurality of episode priority types, wherein each priority type linked list comprises data storage nodes allocated to episodes of a particular type linked in an order that corresponds to when the episodes occurred; and

,

freeing previously allocated data storage nodes for allocation to a present episode when the unallocated list is empty by freeing the oldest data storage node from one of the priority type lists.

23. The method of claim 22 wherein data storage nodes are freed from priority type lists according to priority unless a specified maximum number of stored episodes of one particular type would then be exceeded.

24. The method of claim 22 wherein the freed previously allocated node for is taken from a lower priority list in preference to a higher priority list.

25. The method of claim 24 further comprising allocating a data storage block to a therapy attempt associated with an episode.

26. The method of claim 25 further comprising storing data collected prior to onset of the episode in a location referenced by the data storage node allocated to the episode.

27. The method of claim 25 further comprising storing data collected before and after the therapy attempt in locations referenced by the data storage node allocated to the attempt.

28. A processor-readable storage medium having processor-executable instructions for performing the method recited in claim 22.