Cardiac Pacemakers, Inc.

Michael W Dooley

William J Linder

Keith R Maile

Ronald A Balczewski

Rodney W Salo

David W Kelly

Arthur L Olive

Brian D Pederson

William L Zimmer

Renold J Russie

Gregory Scott Munson

Jean-Cheui Hsung

William A Palm

Richard J Wessels

Lloyd A Van Hofwegen

Suneel Arora

Terrence L Marshall

Jeffrey Laackmann

Brian P Citak

A differential discrete-time signal processing channel differentially processes cardiac signals in an implantable cardiac rhythm management device. Such signal processing effectively uses downsampling to uses lower bias currents, thereby saving power and prolonging the life of the implanted device, and also reduces clock feedthrough, provides a wider dynamic range and better rejection of power supply noise. The device includes a continuous-time buffer, a decimator/averager and/or other filter and/or amplifier circuits, and an analog-to-digital converter, each configured for processing differential signals. The device also includes an operational transconductance amplifier (OTA), for the discrete-time differential signal processing. The OTA provides, among other things, an output common mode adjustment circuit and an offset compensation circuit.

Amplifier with common mode and offset correction

An apparatus and method for determining the condition of a battery in an implantable cardioverter/defibrillator. A battery's operating status is determined from measurements of its open circuit voltage and the time required to charge an energy storage capacitor.

Apparatus and method for estimating battery condition in implantable cardioverter/defibrillators

Cardiac rhythm management system with differential sensing channel

A current and temperature compensated voltage reference circuit uses a power supply voltage as low as 1.3 Volts. A folded-cascode amplifier measures the temperature dependent voltages provided by first and second bias circuits, each including two series-coupled diodes or diode-connected bipolar junction transistors (BJTs), and provides a resulting proportional to absolute temperature (PTAT) current through a cascode-protected output transistor. A voltage reference circuit uses a PTAT current through a resistor to create a PTAT voltage in series with a diode-voltage. The resistor value is adjusted until the sum of these voltages is equal to the bandgap voltage of silicon, providing a temperature compensated voltage reference. The reference circuit is suitable for use with an implantable cardiac rhythm management system having a battery that provides a power supply voltage varying approximately between 1.3 Volts and 3.25 Volts. Cascode-protected current mirrors further improve rejection of such variations in the power supply voltage.

Current and temperature compensated voltage reference having improved power supply rejection

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 multi-pole pacing/sensing lead is used to measure the instantaneous impedance in the right ventricle of a patient's heart. The resulting impedance waveform is signal processed to obtain a measure of the time interval beginning with the occurrence of a paced beat or a spontaneous QRS complex (systole marker) and ending with the point where the impedance versus time signal crosses the zero axis in the positive direction following the paced or spontaneous QRS complex initiating the interval or some other predetermined point along the positive-going waveform. The resulting time interval is inversely proportional to the contractility of the heart and is found to decrease with exercise and the introduction of catecholamines. Thus, it can be used as a control parameter for a demand-type cardiac pacemaker. A means for obviating changes in pacing rate due to long-term drift in the impedance sensing circuitry is also disclosed.

Physiologic control of pacemaker rate using pre-ejection interval as the

Growing community of inventors

Saint Paul, MN, United States of America

Michael W Dooley