Cardiac pacemaker with table-based pacing mode implementation

Abstract

A device and method for implementing a bradycardia pacing mode are disclosed which is mostly hardware-based but still allows the flexibility for making major changes in brady behavior normally found only in firmware-based implementations. The brady behavior of the device is encapsulated by a table in an area of RAM referred to as brady RAM, and the brady behavior can be changed by re-loading the brady RAM with a different table.

1 . A method for operating a cardiac pacemaker, comprising:
 sensing cardiac events;   detecting states of one or more timers;   mapping particular device states defined by timer states and/or sensed events to associated device actions which include pacing pulse delivery in accordance with a bradycardia pacing mode and/or changes in timer states in a brady table contained in a brady RAM; and,   comparing current timer states and sensed events to a device state contained in the brady table and, if found to match, causing performance of the associated device action.   
     
     
         2 . The method of  claim 1  further comprising accessing the brady RAM by means of a microprocessor and reloading the brady RAM with a different brady table to modify the pacing mode. 
     
     
         3 . The method of  claim 1  wherein the brady table is made up of condition words representing particular device states and corresponding action words representing particular device actions. 
     
     
         4 . The method of  claim 3  wherein each condition word represents a particular device state according to whether particular bits of the word are set or cleared, and each action word represents particular actions which can be performed by the device according to whether particular bits of the word are set or cleared. 
     
     
         5 . The method of  claim 4  wherein the current state of the pacemaker is represented by a set of timer outputs and a set of sensing comparator outputs which form a current status word, and further wherein the condition words in the brady table are constructed with a bit-by-bit correspondence to the current status word. 
     
     
         6 . The method of  claim 4  wherein the actions which may be taken by the pacemaker in implementing a bradycardia pacing mode are represented by a set of action inputs which may include timer inputs and a set of pacing pulse generator inputs which cause delivery of paces to particular pacing electrodes, and further wherein the action words in the brady table are constructed with a bit-by-bit correspondence to the set of available action inputs. 
     
     
         7 . The method of  claim 6  wherein an action input is provided for causing a particular event represented in the current status word to be stored in a FIFO queue along with a time stamp. 
     
     
         8 . The method of  claim 4  further comprising sequentially comparing condition words with the current status word when a bit of the current status word changes as detected by a state change detector. 
     
     
         9 . The method of  claim 5  wherein the current status word further comprises one or more state register outputs which are used to affect device behavior. 
     
     
         10 . The method of  claim 9  wherein a state register output signifies detection of a noisy condition in a particular sensing channel. 
     
     
         11 . A cardiac pacing device, comprising:
 means for sensing cardiac events;   means for detecting states of one or more timers;   means for mapping particular device states defined by timer states and/or sensed events to associated device actions which include pacing pulse delivery in accordance with a bradycardia pacing mode and/or changes in timer states in a brady table contained in a brady RAM; and,   means for comparing current timer states and sensed events to a device state contained in the brady table and, if found to match, causing performance of the associated device action.   
     
     
         12 . The device of  claim 11  further comprising means for accessing the brady RAM with a microprocessor and reloading the brady RAM with a different brady table to modify the pacing mode. 
     
     
         13 . The device of  claim 11  wherein the brady table is made up of condition words representing particular device states and corresponding action words representing particular device actions. 
     
     
         14 . The device of  claim 13  wherein each condition word represents a particular device state according to whether particular bits of the word are set or cleared, and each action word represents particular actions which can be performed by the device according to whether particular bits of the word are set or cleared. 
     
     
         15 . The device of  claim 14  wherein the current state of the device is represented by a set of timer outputs and a set of sensing comparator outputs which form a current status word, and further wherein the condition words in the brady table are constructed with a bit-by-bit correspondence to the current status word. 
     
     
         16 . The device of  claim 14  wherein the actions which may be taken by the device in implementing a bradycardia pacing mode are represented by a set of action inputs which may include timer inputs and a set of pacing pulse generator inputs which cause delivery of paces to particular pacing electrodes, and further wherein the action words in the brady table are constructed with a bit-by-bit correspondence to the set of available action inputs. 
     
     
         17 . The device of  claim 16  wherein an action input is provided for causing a particular event represented in the current status word to be stored in a FIFO queue along with a time stamp. 
     
     
         18 . The device of  claim 14  further comprising means for sequentially comparing condition words with the current status word when a bit of the current status word changes as detected by a state change detector. 
     
     
         19 . The device of  claim 15  wherein the current status word further comprises one or more state register outputs which are used to affect device behavior. 
     
     
         20 . The device of  claim 19  further comprising a state register output that signifies detection of a noisy condition in a particular sensing channel.