Cardiac Pacemakers, Inc.

Angeion Corporation

Jean-Cheui Hsung

Lloyd A Van Hofwegen

William A Palm

Keith R Maile

William J Linder

Frank R Dropps

David W Kelly

Michael W Dooley

Richard J Wessels

Mark A Stockburger

Daniel E Huntwork

Sharon Johnson

James Marcotte

Jeffrey Laackmann

A power management system for an implantable device is disclosed. One application is an implantable cardioverter/defibrillator. Charging circuits for implantable cardioverter/defibrillators require relatively large currents from the power supply. The present power management system provides extended device operation and reduced charge cycle time. The present system monitors both current and voltage drawn from the power supply to prevent a loss of system voltage. Elective replacement indication is performed using charging information provided by the present power management system.

Power management system for an implantable device

A deterministic and jitter-free dual chamber brady pacemaker utilizes both a programmed microprocessor and a hardware state machine, both of which are coupled to a real time clock (RTC), random access memory (RAM) and a common escape interval timer. Time of occurrence (TOC) data representative of the time and nature of atrial and ventricular sensed events and pacing events is stored in the RAM. Escape interval periods are timed by the escape interval timer. The microprocessor is operable in both an active mode and an inactive mode without interrupts. In response to the receipt of wakeup commands, the microprocessor operates in the active mode and uses the TOC data from the RAM to reset the escape interval timer to a desired next event interval. The hardware state machine uses the common escape interval timer for timing timeout events and atrial and ventricular sensed events such that pacing pulses are delivered in a determinate manner.

Deterministic and jitter-free dual-chamber cardiac pacemaker

A tiered therapy cardiac detection system is provided for a medical device that senses cardiac signals representative of beat-to-beat intervals and delivers at least one therapy in response to a detected cardiac dysrhythmia corresponding to one of a plurality of programmed zones of heart rates. The detection system includes a global counter that counts at least all beat-to-beat intervals indicating a rate greater than a programmed threshold value representative of a minimum heart rate for delivering any therapy once an initial threshold condition is met. A plurality of window memories and parameter memories are provided in the device. Each window memory corresponds to a given one of the zones and stores an indication of whether each of a last N cardiac signals are within that zone. Each parameter memory corresponds to a given one of the zones and stores a programmed trigger value of the global counter required in order for a therapy in that zone to be delivered. Processing circuitry evaluates the global counter, the window memories and the parameter memories on a beat-by-beat basis and indicates that a cardiac dysrhythmia has been detected for a given zone if the global counter exceeds the programmed trigger value for that zone and the indications stored by the window memory for that zone satisfy a predetermined criteria.

Tiered therapy cardiac detection system having a global counter

An arrhythmia detector includes a delta modulator which digitizes the ECG signal and produces a serial digital signal that represents the input ECG signal. A microprocessor classifies the signal as having no slope, positive slope, or negative slope. A finite state machine model in the microprocessor uses the positive slope, negative slope, or no slope information to determine the number of times an isoelectric line segment is present in the ECG signal. By accumulating the line-counts or number of line segments over a two-second period, a determination can be made whether the ECG signal has been in isoelectric line less than a threshold. For two out of three 2 second periods, if the percentage of isoelectric time is less than the ventricular fibrillation threshold then a ventricular fibrillation signal can be generated. For ventricular tachycardia verses supraventricular tachycardia discrimination, a second threshold which relates to the average heart rate observed in a linear formula LC(TH)=b-a*(rate)/30 can be used. If the isoelectric line-count is less than the LC(TH), then VT is declared. The regression coefficient a and b can be found by measuring the line-count and rate pairs in 2 second periods during normal sinus rhythm in periodic basis, for example, 10 data pairs every hour. The delta modulator uses a comparator which receives the ECG signal and a tracking signal to output a series of binary digits. A digital-to-analog converter generates the tracking signal.

Arrhythmia detector using delta modulated turning point morphology of

An automatic implantable defibrillator/cardioverter having a non-committed defibrillation/cardioversion algorithm. The defibrillator/cardioverter includes an ECG amplifier with automatic gain control (AGC) which detects the electrical activity of the heart for analysis by a cardiac condition detector. Logic is provided which receives input from the ECG amplifier and the cardiac condition detector for analyzing the heart activity. The non-committed defibrillation algorithm sensing begins upon the determination of an arrhythmia. The capacitor is charged while the heart activity is simultaneously monitored. After the capacitor is charged, a check is made on the duration of the last detected R-R interval while so charging the capacitor, and a comparison is made between this R-R interval and a preset value. If the last R-R interval is greater than the preset value, a non-committing period is entered which lasts approximately 2 seconds. The purpose of the non-committing period is to allow detection to monitor the arrhythmia further before making the decision to discharge the capacitor or dump the charge internally. If any R-R interval detected during this interval is less than PCLL, this indicates that the arrhythmia has not reverted and the capacitor charge is delivered to the patients, synchronously with the second R-wave of the fast R-R interval. If no rapid interval is detected during this time, a post intervention (PI) monitoring routine is entered at the end of the non-committing period to further monitor cardiac activity and shock if necessary.

Defibrillation/cardioversion system with multiple evaluation of heart

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Shoreview, MN, United States of America

Jean-Cheui Hsung