Assessment of cardiac output by implantable medical device

• US 7,925,347 B1
• Filed: 11/26/2007
• Issued: 04/12/2011
• Est. Priority Date: 11/26/2007
• Status: Expired due to Fees

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Inventors: Bornzin, Gene A.
• Primary Examiner(s): Layno; Carl H
• Assistant Examiner(s): Stice; Paula J
• Application Number:
  US11/945,025
• Time in Patent Office: 1,233 Days
• Field of Search: 607 18- 25, 600303-336
• US Class Current: 607/22
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: A61B 5/6885 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61N 1/36557 controlled by chemical substances in blood
• CPC Class Codes: A61N 1/395 for treating atrial fibrillation

Abstract

An implantable medical device calculates cardiac output on a repeated basis based on acquired cardiac information that relates to one or more parameters of the Fick equation, including venous oxygen saturation, arterial oxygen saturation, estimated oxygen consumption and hemoglobin information. In some aspects, the estimated oxygen consumption may be based on the activity of a patient. For example, respiratory-related information and/or temperature related information may be used to determine the activity level of the patient. In addition, trends relating to heart function may be identified based on cardiac output calculations that are generated over time.

Claims

1. A method of identifying a heart function trend, said method comprising:

acquiring venous oxygen saturation information via an implantable sensor;

acquiring arterial oxygen saturation information;

calculating estimates of oxygen consumption by multiplying a basic metabolic rate (BMR) by an activity based parameter;

deriving a series of cardiac output measurements based on the venous oxygen saturation information, the estimates of oxygen consumption, and the arterial oxygen saturation information; and

generating a histogram of cardiac output measurements as a function of activity level.

2. The method of claim 1, wherein the activity based parameter comprises an acceleration-based factor.

3. The method of claim 1, wherein the activity based parameter comprises a respiratory-based factor.

4. The method of claim 3 wherein the respiratory-based factor comprises one of respiratory rate, respiratory volume and minute ventilation.

5. The method of claim 1, further comprising identifying a trend in cardiac output as a function of activity level;

and adapting cardiac therapy based on the identified trend.

6. The method of claim 1, further comprising acquiring hemoglobin-related information via a third implantable sensor, wherein the derivation of cardiac output measurements is further based on the hemoglobin-related information.

7. A method of deriving an indication of cardiac output by an implantable medical device, said method comprising:

acquiring venous oxygen saturation information via a first implantable sensor;

acquiring hemoglobin-related information via a second implantable sensor;

calculating estimates of oxygen consumption by multiplying a basic metabolic rate (BMR) by an activity based parameter; and

deriving cardiac output measurements based on the venous oxygen saturation information, the hemoglobin-related information, and the estimates of oxygen consumption.

8. The method of claim 7, wherein the second implantable sensor comprises an optical sensor.

9. The method of claim 7, wherein the second implantable sensor comprises an impedance sensor.

10. The method of claim 7, further comprising determining a pacing rate during atrial fibrillation based on the cardiac output measurements.

11. The method of claim 7, further comprising not administering a shock during ventricular tachyarrhythmia if the cardiac output measurements indicate that cardiac output is substantially stable.

12. The method of claim 7, further comprising:

determining whether a patient is at rest; and

adjusting at least one pacing parameter based on the cardiac output measurements to optimize cardiac output.

13. The method of claim 7, further comprising:

generating a histogram of the cardiac output measurements as a function of the hemoglobin-related information;

identifying a trend in the cardiac output measurements based on the histogram; and

adapting treatment for a patient based on the identified trend.

14. An implantable medical device comprising:

an implantable venous oxygen saturation sensor adapted to provide S_VO2 measurements;

an implantable arterial oxygen saturation sensor adapted to provide S_AO2 measurements;

an implantable hemoglobin sensor adapted to provide hemoglobin information;

an oxygen consumption estimator adapted to calculate estimates of oxygen consumption by multiplying a basic metabolic rate (BMR) by an activity based parameter; and

a cardiac output calculator adapted to derive an indication of cardiac output based on the S_VO2 measurements, the S_AO2 measurements, the hemoglobin information and the estimates of oxygen consumption.