Implantable lead functional status monitor and method

In a cardiac pacing system of the type comprising an implantable pulse generator for sensing cardiac activity and providing pacing pulses to at least one chamber of the heart through a pacing path, the pacing path comprising at least one pair of pace/sense electrodes, a like pair of electrode/tissue interfaces, and the body and heart tissue located therebetween, and at least one lead extending from the implantable pulse generator to the heart and locating at least one of the pace/sense electrodes of each pair at a site in relation to a heart chamber, each lead comprising an elongated lead body extending between a lead connector element at a lead proximal end adapted to be coupled with the implantable pulse generator at a connector interface and a lead distal end, the lead body supporting at least one exposed pace/sense electrode adapted to interface with tissue at an electrode/tissue interface and enclosing at least one electrical conductor within a lead body insulating sheath extending between the exposed electrode and the lead connector element,

• a lead status monitoring method for processing lead related data in a system self test mode and providing, for each lead pacing path, a lead status report that identifies suspected lead related condition mechanisms as suspected conductor/connector open circuit issues, insulation degradation issues and electrode/tissue interface issues, the method comprising the steps of:
• establishing a set of lead status monitor rules related to implied lead related condition mechanisms of each conductor itself, its connector interface, its insulation degradation, and its electrode/tissue interface;
• periodically, measuring the impedance of the lead or leads in the pacing path and deriving a measured lead impedance;
• periodically conducting a pacing threshold test varying pacing pulse energy and monitoring the response of the heart chamber to determine a loss of capture pulse energy level at which the applied pacing pulse energy fails to capture the heart chamber;
• subjecting the measured lead impedance and the loss of capture pulse energy level to the set of lead status monitor rules;
• and
• generating the lead status report for the pacing path identifying any conductor/connector open circuit issues, insulation degradation issues, and electrode/tissue interface issues that are implied when the measured lead impedance and loss of capture pulse energy level satisfy one or more of the set of lead status monitor rules.

In an implantable medical device capable of delivering stimulation energy to the body for triggering a stimulus response, a lead status monitor for processing lead related data in a system self test mode and providing, for each lead, a lead status report that identifies suspected lead related condition mechanisms as suspected conductor/connector issues, insulation degradation issues and electrode/tissue interface issues, comprising:

• an implantable pulse generator adapted to be coupled to one or more lead at a connector interface,
• at least one lead comprising an elongated lead body extending between a lead connector element at a lead proximal end adapted to be coupled with the implantable pulse generator at the connector interface and a lead distal end, the lead body supporting an exposed electrode adapted to interface with tissue at an electrode/tissue interface and enclosing at least one electrical conductor within a lead body insulating sheath extending between the exposed electrode and the lead connector element,
• means for establishing a set of lead status monitor rules related to the implied lead related condition mechanisms of each conductor, the connector interface, insulation degradation, and the electrode/tissue interface;
• means for periodically measuring the impedance of the lead and deriving a measured lead impedance;
• means for periodically conducting a stimulation threshold test varying stimulation energy and monitoring the stimulus response to determine a loss of capture stimulation energy level at which the applied electrical stimulation energy fails to trigger a stimulus response;
• means for subjecting the measured lead impedance and the loss of capture stimulation energy level to the set of lead status monitor rules;
• and
• means for generating the lead status report identifying any conductor/connector issues, insulation issues, and electrode/tissue interface issues that are implied when the measured lead impedance and loss of capture stimulation energy level satisfy one or more of the set of lead status monitor rules.

In a cardiac pacing system, a lead status monitoring method for processing lead related data in a system self test mode and providing, for each lead pacing path, a lead status report that identifies suspected lead related condition mechanisms as suspected conductor/connector open circuit issues, insulation degradation issues and electrode/tissue interface issues, comprising:

• an implantable pulse generator for sensing cardiac activity and providing pacing pulses to at least one chamber of the heart through a pacing path, the pacing path comprising at least one pair of pace/sense electrodes, a like pair of electrode/tissue interfaces, and the body and heart tissue located therebetween
• at least one lead extending from the implantable pulse generator to the heart and locating at least one of the pace/sense electrodes of each pair at a site in relation to a heart chamber, each lead comprising an elongated lead body extending between a lead connector element at a lead proximal end adapted to be coupled with the implantable pulse generator at a connector interface and a lead distal end, the lead body supporting at least one exposed pace/sense electrode adapted to interface with tissue at an electrode/tissue interface and enclosing at least one electrical conductor within a lead body insulating sheath extending between the exposed electrode and the lead connector element,
• means for establishing a set of lead status monitor rules related to implied lead related condition mechanisms of each conductor, the connector interface, insulation degradation, and the electrode/tissue interface;
• means for periodically, measuring the impedance of the lead or leads in the pacing path and deriving a measured lead impedance;
• means for periodically conducting a pacing threshold test varying pacing pulse energy and monitoring the response of the heart chamber to determine a loss of capture pulse energy level at which the applied pacing pulse energy fails to capture the heart chamber;
• means for subjecting the measured lead impedance and the loss of capture pulse energy level to the set of lead status monitor rules;
• and
• means for generating the lead status report for the pacing path identifying any conductor/connector open circuit issues, insulation degradation issues, and electrode/tissue interface issues that are implied when the measured lead impedance and loss of capture pulse energy level satisfy one or more of the set of lead status monitor rules.