Pacesetter, Inc.

Steven W Badelt

Gabriel A Mouchawar

Jorge N Amely-Velez

Mark W Kroll

Dro Darbidian

J Christopher Moulder

George I Isaac

Anne M Street

An output circuit for use in an implantable cardiac defibrillation provides an output pulse having a waveform of virtually any desired shape. The device includes a sensing circuit that senses cardiac activity. An arrhythmia detector detects fibrillation responsive to the cardiac activity signal. The device further includes an output circuit that provides a stimulation output pulse when the arrhythmia detector detects a cardiac arrhythmia. The output circuit includes an H-bridge having a pair of switching devices which control the output pulse waveform with pulse-width modulation and a second pair of switching devices that control the output pulse polarity.

Implantable cardiac stimulation device including an output circuit that provides arbitrarily shaped defibrillation waveforms

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.

System and method for measuring lead impedance in an implantable stimulation device employing pulse-train waveforms

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. By providing dual RAM and ROM, software upgrades or software bug fixes are easily performed merely by downloading new software into RAM, then resetting the zone control register to point to RAM, rather than ROM. Additionally, when necessary, the overall virtual memory space may be expanded to encompass both the RAM and ROM thereby permitting access to greater quantities of memory.

Implantable medical stimulation device having reconfigurable memory

By redistributing the running totals for various preliminary classifications to other preliminary classifications based upon the values of the most recent cardiac events, the present invention biases the running totals (thereby biasing the duration criteria) to help overcome common discrimination problems which permits the stimulation device to make a correct and final therapy decision more quickly. To identify a patient's heart rhythm, various electrical events such as P-waves and R-waves, and their timing, relationship, and stability, are detected and a preliminary classification is made for each detected event. Running totals of the numbers of all events detected within each of the preliminary classifications are maintained, along with sliding totals covering only the most recently detected events. Then, the arrhythmia is identified based upon an analysis of both the running totals and the sliding totals. In a preferred embodiment, the arrhythmia is identified by first determining whether the sliding total of the number of detected events in any one of the preliminary classifications exceeds a corresponding sliding total threshold. If so, the running totals are then selectively redistributed based upon the sliding totals. The final decision is then made based upon whether the running total corresponding to any one of the preliminary classifications exceeds a corresponding running total threshold. Both method and apparatus embodiments are disclosed. Methods are further described for determining the preliminary classifications of the detected events.

Implantable stimulation device and method for discrimination atrial and ventricular arrhythmias

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. When the automatic capture function is enabled, the stimulation device initiates a stimulation refractory period, upon the expiration of which, the stimulation device sets a sensing threshold to a predetermined level and then either maintaining this level fixed or causing it to decay, during an alert interval. Concurrently, the stimulation device verifies capture during the alert interval.

System and method of performing automatic capture in an implantable cardiac stimulation device

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. By providing dual RAM and ROM, software upgrades or software bug fixes are easily performed merely by downloading new software into RAM, then resetting the zone control register to point to RAM, rather than ROM. Additionally, when necessary, the overall virtual memory space may be expanded to encompass both the RAM and ROM thereby permitting access to greater quantities of memory.

An implantable cardioverter/defibrillator applies a quantity of electrical energy to a heart to terminate an arrhythmia of the heart. The cardioverter/defibrillator employs therapy delivery timing to avoid delivery of the therapy during vulnerable periods of the heart. The cardioverter/defibrillator includes an arrhythmia detector that detects an arrhythmia of the heart, a ventricular activation detector that detects ventricular activations of the heart, and an atrial activation detector that detects atrial activations of the heart. A ventricular timer, resettable by detected ventricular activations, and an atrial timer, resettable by detected atrial activations, keep time responsive to the arrhythmia detector detecting the arrhythmia. A generator applies the quantity of electrical energy to the heart responsive to the arrhythmia detector detecting the arrhythmia, when neither chamber is in its vulnerable period.

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Granada Hills, CA, United States of America

Steven W Badelt