Biomedical method and apparatus for controlling the administration of therapy to a patient in response to changes in physiological demand

• US 5,190,035 A
• Filed: 04/17/1986
• Issued: 03/02/1993
• Est. Priority Date: 06/18/1981
• Status: Expired due to Term

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Salo, Rodney W., Pederson, Brian D.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US06/853,059
• Time in Patent Office: 2,511 Days
• Field of Search: 128/419 PG
• US Class Current: 607/24
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance

Abstract

A biomedical apparatus capable of sensing changes in the heart'"'"'s ventricular volume or stroke volume and then changing the operating performance of the device in a fashion as a function of stroke volume. A relatively low frequency signal (under 5 KHz) is applied between spaced electrodes disposed in the heart and the beating action of the heart serves to modulate this signal due to changes in impedance being sensed between these or other electrodes within the heart. The modulated carrier signal is then processed to remove R-wave and other electrical artifacts and then demodulated to remove the carrier frequency component leaving the envelope which is proportional to instantaneous ventricular volume. This envelope signal then contains stroke volume and ventricular volume information which can be used by the biomedical apparatus to vary its operating parameters. For example, a current proportional to changes in stroke volume may be injected into the timing circuit of a demand-type cardiac pacer pulse generator whereby the interpulse interval of the pulse generator is varied as a function of stroke volume.

Claims

1. A cardiac pacer for the therapeutic-stimulation of a heart comprising:

lead system means for coupling said pacer to the patient'"'"'s heart;

measuring means coupled to said lead for inferring the stroke volume of said heart from the measurement of a physiologic parameter and for producing measurement indicative of stroke volume;

computation and control means coupled to said measuring means for determining a heart rate value in response to said stroke volume measurements wherein said heart rate is defined as the V--V interval;

means for comparing the value of said stroke volume measurement with the value of a stroke volume set point for producing a stroke volume difference value;

means for determining a heart rate difference value, wherein said heart rate value is defined as the V--V interval, from said stroke volume difference value;

means for adding said heart rate different value to the previous heart rate value yielding a current, heart rate value; and

pulse generator means coupled to said lead system and said computational and control means for providing stimulation pulses to said heart at a frequency which is a function of said heart rate value.

2. A cardiac pacer for the therapeutic stimulation of a heart comprising:

lead system means for coupling said pacer to the patient'"'"'s heart;

measuring means coupled to said lead for inferring the stroke volume of said heart from the measurement of a physiologic parameter and for producing a measurement signal indicative of stroke volume;

signal processing means coupled to said measuring means for determining heart rate values in response to said stroke volume measurement signal wherein said heart rate is defined as the V--V interval;

means for comparing the value of said stroke volume measurement signal with the value of a set point for producing a stroke volume difference value;

means for determining a heart rate difference value, from said stroke volume difference value wherein said heart rate value is defined as the V--V interval;

means for adding said heart rate difference value to the previous heart rate value yielding a current heart rate value; and

pulse generator means coupled to said lead system and said signal processing means for providing stimulation pulses to said heart at a frequency which is a function of said current heart rate value.