Abstract: Disclosed herein is a shield for shielding a telemetry wand from electromagnetical interference capable of interfering with telemetry communications between the telemetry wand and an AIMD in a patient. The telemetry wand may include a first side that is configured to be placed against a patient, a second side generally opposite the first side, a lateral side between the first and second sides, a hole extending between the first and second sides, and a cable extending from the lateral side. The shield may include a shell including a wall that defines a volume and an opening in the shell. The volume may be configured to receive therein the telemetry wand such that the second and lateral sides of the telemetry wand face respective portions of the wall and the first side faces the opening in the shell.

Abstract: Disclosed herein is a shield for shielding a telemetry wand from electromagnetical interference capable of interfering with telemetry communications between the telemetry wand and an AIMD in a patient. The telemetry wand may include a first side that is configured to be placed against a patient, a second side generally opposite the first side, a lateral side between the first and second sides, a hole extending between the first and second sides, and a cable extending from the lateral side. The shield may include a shell including a wall that defines a volume and an opening in the shell. The volume may be configured to receive therein the telemetry wand such that the second and lateral sides of the telemetry wand face respective portions of the wall and the first side faces the opening in the shell.

Abstract: A leakage detection system for use in an implantable cardiac stimulation device, such as a cardioverter defibrillator. The leakage detection system includes a switch bank and a controller that regulates the switching arrangements of various switches. The leakage detection system causes pulse generators to generate a pulse-train waveform comprised of a sequence of pulses of opposite polarities, and to deliver these pulses in a preselected temporal relation. The controller detects the current leakage from the pulse generator to the tissues by sensing and analyzing the voltage or current of the pulse generator, leads, and electrodes. The pulsatility and alternating polarities of biphasic pulse-train waveforms increase the stimulation threshold of the motor or sensory nerves and excitable tissues.

Abstract: A method of operating an implantable medical device containing a Lithium Silver Vanadium Oxide battery. In response to a detected need for therapy, a current flow is delivered from the battery to a charge storage device. After the battery is at least partly depleted by one or more such deliveries of current or other power consumption, the battery is recharged. The recharging may be initiated in response to a selected time threshold, a selected number of current flow delivery events, a selected voltage level, an excess charge time duration, or other operating characteristics. A limited number of recharging cycles may be provided if the charging is done under controlled conditions with respect to charge current and voltage.

Abstract: The implantable medical device is provided with typically equal portions of both random access memory (RAM) and read only memory (ROM) and a virtual memory space is defined equal to the amount of memory in one of the memory devices. In a specific example, the RAM and ROM provide 256 K of memory each, with the virtual memory space also set to 256 K. A zone control register is provided which specifies, for each of a set of predetermined zones within the virtual memory space, whether memory access commands are to be routed to RAM or ROM. Control bits within the zone control register may be reset to permit portions of memory to be remapped from one memory device to the other. By providing RAM and ROM each typically equal in size to the virtual memory space, software for use in the device may be tested and debugged using RAM then transferred to ROM for use in production devices.

Abstract: A technique is described for timing hardware or software events for use in an implantable medical device capable of performing many concurrent processes. The technique exploits a first timer for timing events using a timing interval of one millisecond and a second timer or clock signal for timing events using a timing interval of two seconds. A receive unit receives timer requests from the many concurrent processes with each timer request specifying a time delay before an interrupt or other timer completion signal is required. A control unit uses either the first timer or the second timer to time the request based upon the time delay and the respective timing intervals. An interrupt or other timer completion signal is issued to the requesting device following the specified time delay as timed by the selected timer.

Abstract: An implantable cardiac stimulation device possessing pacing, cardioversion and defibrillation functions and automatic capture capabilities, for automatically verifying capture during stimulation operations and, as necessary, automatically delivering back-up stimulation pulses when capture is lost, and subsequently adjusting the stimulation energy to a level safely above that needed to achieve capture. The stimulation device utilizes a method for maintaining capture by means of a capture search algorithm, so that whenever loss of capture is detected, it re-determines the minimum stimulation energy required to achieve capture. Another aspect of the stimulation device is the automatic threshold testing which is invoked to determine the minimum stimulation pulse energy needed to ensure capture.

Abstract: The implantable medical device is provided with typically equal portions of both random access memory (RAM) and read only memory (ROM) and a virtual memory space is defined equal to the amount of memory in one of the memory devices. In a specific example, the RAM and ROM provide 256K of memory each, with the virtual memory space also set to 256K. A zone control register is provided which specifies, for each of a set of predetermined zones within the virtual memory space, whether memory access commands are to be routed to RAM or ROM. Control bits within the zone control register may be reset to permit portions of memory to be remapped from one memory device to the other. By providing RAM and ROM each typically equal in size to the virtual memory space, software for use in the device may be tested and debugged using RAM then transferred to ROM for use in production devices.

Abstract: An implantable cardiac stimulation device possessing pacing, cardioversion and defibrillation functions and automatic capture capabilities, for automatically verifying capture during stimulation operations and, as necessary, automatically delivering back-up stimulation pulses when capture is lost, and subsequently adjusting the stimulation energy to a level safely above that needed to achieve capture. The stimulation device utilizes a method for maintaining capture by means of a capture search algorithm, so that whenever loss of capture is detected, it re-determines the minimum stimulation energy required to achieve capture. Another aspect of the stimulation device is the automatic threshold testing which is invoked to determine the minimum stimulation pulse energy needed to ensure capture.

Abstract: A technique is described for timing hardware or software events for use in an implantable medical device capable of performing many concurrent processes. The technique exploits a first timer for timing events using a timing interval of one millisecond and a second timer or clock signal for timing events using a timing interval of two seconds. A receive unit receives timer requests from the many concurrent processes with each timer request specifying a time delay before an interrupt or other timer completion signal is required. A control unit uses either the first timer or the second timer to time the request based upon the time delay and the respective timing intervals. An interrupt or other timer completion signal is issued to the requesting device following the specified time delay as timed by the selected timer.

Abstract: A technique is described for timing hardware or software events for use in an implantable medical device capable of performing many concurrent processes. The technique exploits a first timer for timing events using a timing interval of one millisecond and a second timer or clock signal for timing events using a timing interval of two seconds. A receive unit receives timer requests from the many concurrent processes with each timer request specifying a time delay before an interrupt or other timer completion signal is required. A control unit uses either the first timer or the second timer to time the request based upon the time delay and the respective timing intervals. An interrupt or other timer completion signal is issued to the requesting device following the specified time delay as timed by the selected timer.

Abstract: An implantable cardiac stimulation device contains a high voltage defibrillating unit. A protection circuit is connected to the defibrillating unit to guard against excessive current during a high voltage discharge. The protection circuit prevents damage to the defibrillation unit and to the associated heart tissue. The defibrillation current is monitored by the protection circuit and if excessive, the defibrillation current is reduced by routing the current through an additional impedance. The protection circuit operates in real-time to remove the additional impedance if the defibrillation current returns to a safe level. A memory device attached to the protection circuit records the event of an excessive defibrillation current.