Method and apparatus for calibrating internal measurements of an implanted cardiac pacer

• US 4,712,179 A
• Filed: 02/05/1987
• Issued: 12/08/1987
• Est. Priority Date: 08/15/1984
• Status: Expired due to Term

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Cordis Corporation (Cardinal Health, Inc.)
• Inventors: Heimer, Malcolm L.
• Primary Examiner(s): Smith, Jerry
• Assistant Examiner(s): HAYES, GAIL O
• Application Number:
  US07/015,492
• Time in Patent Office: 306 Days
• Field of Search: 128/419 PT, 128/419 PG, 128/903 P, 128/417, 128/413, 364/417, 364/571, 331/65
• US Class Current: 607/27
• CPC Class Codes: A61N 1/37252 Details of algorithms or data aspects of communication system, e.g. handshaking, transmitting specific data or segmenting data
• CPC Class Codes: G16H 40/40 for the management of medical equipment or devices, e.g. scheduling maintenance or upgrades
• CPC Class Codes: Y10S 128/903 Radio telemetry

Abstract

An implantable cardiac pacer having pacer circuitry for producing output stimulation pulses on leads connectable to a patient'"'"'s heart includes internal measurement circuitry for producing uncorrected measurement values relative to battery conditions and to pulses from the pacing circuitry. The pacer has a data processing unit with a microprocessor and a RAM device for storing, in dedicated locations, programmed gain and offset correction factors for the uncorrected measurement values. Telemetry means is responsive to the microprocessor for transmitting the uncorrected measurement values and the correction factors to an external programmer/receiver unit. The programmer/receiver unit includes telemetry means for receiving the uncorrected measurement values and the correction factors from the pacer. The programmer/receiver unit further includes a data processing device having an ROM device for storing an algorithm and a microprocessor for calculating corrected measurement values from the uncorrected measurement values and the correction factors.

Claims

1. A method of calibrating internal measurements obtained through plated resistors formed on an integrated circuit in an implanted cardiac pacer, comprising the steps of:

measuring uncorrected values through plated resistors by an internal measurement circuit relative to at least one of battery conditions and pulses from a pacing circuit;

obtaining correct values during the manufacturing process by a precise external instrument relative to at least one of the battery conditions and the pulses from the pacing circuit;

comparing the uncorrected values with the correct values in order to provide correction factors;

storing the correction factors for the uncorrected values in a memory device located within the implant;

telemetering uncorrected values and the correction factors to an external programmer/receiver;

computing corrected values in the external programmer/receiver from the telemetered uncorrected values and the telemetered correction factors in order to compensate effectively for the difference between the actual values of the resistors and the precise values of the resistors, so that the necessity of mechanically trimming the resistors to be of precise values after manufacturing is eliminated.

2. A method as described in claim 1, including the step of displaying the corrected values in the external programmer/receiver.

3. A method as described in claim 1, including the step of connecting a dummy load representing the atrial heart chamber to the leads of a pacer during the steps of (a) measuring uncorrected values by an internal measurement circuit and (b) obtaining correct values by an external instrument.

4. A method as described in claim 3, in which the correction factors include a gain correction factor and an offset correction factor.

5. A method as described in claim 1, in which internal measurements are made of a maximum current output pulse and a minimum current output pulse and external measurements are made of an exact maximum current output pulse and an exact minimum output pulse.

6. A method as described in claim 5, in which the correction factors include a gain factor and an offset factor that is computed by comparing the differences between the external measurements and the internal measurements.