Implantable cardiac rhythm management device for assessing status of CHF patients

• US 6,459,929 B1
• Filed: 04/12/2000
• Issued: 10/01/2002
• Est. Priority Date: 11/04/1999
• Status: Expired due to Term

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Nelson, James P., Stahmann, Jeffrey E., Hopper, Donald L., Jones, Bruce R.
• Primary Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US09/547,519
• Time in Patent Office: 902 Days
• Field of Search: 607/17-20, 600/547, 600/508, 600/513, 600/483, 600/481
• US Class Current: 600/513
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters

Abstract

A method and apparatus for providing congestive heart failure therapy status. An electronic device, preferably a cardiac rhythm management device, capable of measuring transthoracic impedance and for sensing a level of physical activity is implanted in a patient. The transthoracic impedance signal is processed to obtain an estimate of the subject'"'"'s minute ventilation, respiratory rate, tidal volume, inspiratory rate and expiratory rate. From accelerometer measured activity, an estimate is obtained of oxygen uptake, carbon dioxide production and work rate. Ratios of tidal volume to respiratory rate, tidal volume to inspiratory time, tidal volume to expiratory time, heart rate to minute ventilation, respiratory rate to minute ventilation, tidal volume to minute ventilation, minute ventilation to oxygen uptake, minute ventilation to carbon dioxide production, minute ventilation to work rate, heart rate to work rate, oxygen uptake to heart rate and other ratios are meaningful status indicators for assessing the efficacy of particular therapy regimens to CHF patients.

Claims

1. Apparatus for monitoring a patient'"'"'s status of congestive heart failure comprising:

(a) an implantable cardiac rhythm management device having a transthoracic impedance sensor for producing signals related to the pumping action of the heart and respiratory activity, a patient activity sensor for producing signals related to patient activity levels and a microprocessor, connected to the transthoracic impedance sensor and the patient'"'"'s activity sensor, for controlling the delivery of cardiac stimulating pulses to the patient'"'"'s heart;

(b) means including the microprocessor for deriving a plurality of respiratory parameters from signals produced by the transthoracic impedance sensor;

(c) an external monitor; and

(d) means for telemetrically transmitting digital information relating to the respiratory parameters from the implantable cardiac rhythm management device to the external monitor, said external monitor including means for computing and displaying predetermined ratios of the respiratory parameters as congestive heart failure status indicators.

2. The apparatus of claim 1 and further including:

(a) means including the microprocessor for deriving a plurality of physiologic parameters from the signals produced by and the activity sensor; and

wherein the means for telemetrically transmitting digital information relating to respiratory activity further selectively telemetrically transmits digital information relating to said physiologic parameters to the external monitor wherein the means for computing and displaying predetermined ratios computes and displays ratios of the physiologic parameters as congestive heart failure status indicators.

3. The apparatus of claim 2 wherein the plurality of physiologic parameters include heart rate, oxygen uptake, and carbon dioxide output.

4. The apparatus of claim 3 wherein the ratios and wherein the cardiac device determines heart rate of the physiologic parameters include minute ventilation to carbon dioxide output and oxygen uptake to heart rate.

5. The apparatus of claim 1 wherein the respiratory parameters include minute ventilation, respiratory rate, tidal volume and inspiratory time.

6. The apparatus of claim 5 wherein the predetermined ratio values of respiratory parameters include the ratio of tidal volume to respiratory rate and tidal volume to inspiratory time, tidal volume to minute ventilation and respiratory rate to minute ventilation.