Device for assessing cardiovascular function, physiological condition, and method thereof

• US 6,511,436 B1
• Filed: 06/16/2000
• Issued: 01/28/2003
• Est. Priority Date: 06/16/1999
• Status: Expired due to Fees

• Current Assignee: Artech Medical
• Original Assignee: Roland Asmar
• Inventors: Asmar, Roland
• Primary Examiner(s): Shaver, Kevin
• Assistant Examiner(s): Mallari, Patricia C.
• Application Number:
  US09/596,273
• Time in Patent Office: 956 Days
• Field of Search: 600/490, 600/405, 600/481, 600/500-504
• US Class Current: 600/500
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves

Abstract

A device to evaluate the arterial wall stiffness using pulse wave velocity measurements is described. The device uses probes to record the pulse wave at different locations on the body. Automatic calculation of the time delay between the proximal and distal waves is performed. Based on the pulse wave velocity values and the brachial pulse pressure, an estimation of the central (aortic) pulse pressure is calculated.

Claims

1. A method for assessing cardiovascular function in a patient comprising the steps of:

obtaining arterial hemodynamic behavior data from the patient at a first recording location;

obtaining arterial hemodynamic behavior data from the patient at at least a second recording location;

extracting data indicative of transit time of the arterial hemodynamic behavior data obtained between the first recording location and second recording location;

measuring distance between the first recording location and the second recording location to obtain distance data;

determining arterial hemodynamic behavior velocity data from the transit time data and the measured distance data; and

correlating the arterial hemodynamic behavior velocity data with a reference value to determine cardiovascular function in the patient.

2. The method of claim 1 wherein the arterial hemodynamic behavior at the second recording location is obtained simultaneously with the arterial hemodynamic behavior obtained at the first recording location.

3. The method of claim 1 further comprising the steps of:

obtaining arterial hemodynamic behavior data from the patient at a third recording location;

extracting data indicative of transit time of the arterial hemodynamic behavior data obtained between the first location and the third location;

measuring distance between the first recording location and the third recording location to obtain distance data;

determining arterial hemodynamic velocity data from the transit time data and the measured distance data between the first recording location and the third recording location;

and correlating the arterial hemodynamic behavior velocity data between the first recording location and the third recording location with a reference value to determine cardiovascular function in the patient.

4. The method of claim 1 further comprising the step of smoothing the data obtained at the first recording location and at the second recording location.

5. The method of claim 4 wherein the smoothing step comprises a low-pass filtering algorithm to process each recording.

6. The method of claim 1 wherein the first recording location is located at a proximal position on an artery and the second recording location is located at a position along an arterial tree distal to the first recording location.

7. The method of claim 1 wherein the first recording location is located over the common carotid artery near the base of the neck of the patient and the second recording location is located over a femoral artery of the patient.

8. The method of claim 1 further comprising the step of digitizing the arterial hemodynamic behavior data obtained from the first recording location and the second recording location.

9. The method of claim 1 wherein the arterial hemodynamic behavior data comprises pulse pressure wave data.

10. The method of claim 1 wherein the arterial hemodynamic behavior data comprises pulse volume wave data.

11. The method of claim 1 wherein the arterial hemodynamic behavior data comprises pulse flow wave data.

12. The method of claim 1 wherein the arterial hemodynamic behavior data comprises arterial diameter wave data.

13. The method of claim 1 further comprising the step of displaying transit time data indicative of cardiovascular function in the patient.

14. The method of claim 1 further comprising the step of displaying the velocity data indicative of cardiovascular function in the patient.

15. The method of claim 1 further comprising obtaining arterial hemodynamic behavior data at a first recording location and at a second recording location during a plurality of respiratory cycles.

16. The method of claim 1 further comprising obtaining arterial hemodynamic behavior at a first recording location and at a second recording location during at least one complete respiratory cycle.

17. The method of claim 1 further comprising the step of comparing the arterial hemodynamic velocity data of the patient with a reference value, wherein a difference in the arterial hemodynamic velocity data of the patient compared to the reference value is indicative of abnormal cardiovascular function of the patient.

18. The method of claim 1 further comprising the step of comparing the arterial hemodynamic behavior velocity data of the patient with arterial hemodynamic behavior velocity data in a preprogrammed library of arterial hemodynamic behavior data in normal and pathologic cardiovascular function, wherein differences between the arterial hemodynamic behavior velocity data of the patient and the arterial hemodynamic behavior velocity data of normal or pathological cardiovascular function, is indicative of cardiovascular function of the patient.

19. The method of claim 1 wherein the cardiovascular function comprises arterial distensibility.

27. The system of claim 19 further comprising a filter to filter out high frequency noise.

28. The system of claim 27 wherein the filter comprises a low-pass filtering algorithm.

20. A system for assessing cardiovascular function in a mammal, comprising:

a first transducer for recording arterial hemodynamic behavior data at a proximal recording site;

at least a second transducer for recording arterial hemodynamic behavior data at a second recording site distal to said proximal recording site;

a data processor for extracting transit time data between an initial upstroke segment of a waveform of the arterial hemodynamic behavior data recorded at the proximal recording site and an initial upstroke segment of a waveform of the arterial hemodynamic behavior data recorded at the distal recording site by repetitively shifting the distal waveform segment toward the proximal waveform segment, wherein the initial upstroke of the waveform recorded at the proximal recording site is determined, and the initial upstroke of the waveform recorded at the distal recording site is determined when a coefficient of correlation is maximal when comparing corresponding areas around the beginning of the upstroke of the waveform recorded at the proximal recording site and at the distal recording site; and

an apparatus for measuring a distance between the first recording site and the second recording site to obtain measured distance data, wherein the processor extracts arterial hemodynamic velocity data from the transit time data and the measured distance data to assess cardiovascular function in the mammal.

21. The system of claim 20 wherein the transducers obtain arterial hemodynamic data comprising arterial diameter data.

22. The system of claim 20 further comprising a display for displaying the arterial hemodynamic velocity data.

23. The system of claim 20 further comprising an analog to digital converter for converting the arterial hemodynamic behavior data from analog form to digital form.

24. The system of claim 20 wherein the transducers obtain arterial hemodynamic data comprising pulse flow data.

25. The system of claim 20 wherein the transducers obtain arterial hemodynamic data comprising pulse pressure data.

26. The system of claim 20 wherein the transducers obtain arterial hemodynamic data comprising pulse volume data.

29. A method for determining the time delay between a proximal and a distal recording site over a patient arterial system, comprising the steps of:

a) measuring a distance between two recording sites over the arterial system of the patient;

b) obtaining simultaneous pulse arterial data in waveform at the two recording sites;

c) calculation of the pulse wave time between the two recording sites as follows;

i) at the first recording site, determine a proximal waveform by identifying a footwave at a beginning of an initial upstroke;

ii) at the second recording site, determine a distal waveform by identifying a footwave of an initial upstroke by searching in the second recording when a coefficient of correlation is maximal when comparing corresponding areas around the proximal and distal waveforms;

iii) determine transit time delay between the two corresponding footwaves in the proximal and distal pulse waveforms; and

d) extracting pulse wave velocity from the distance between the two recording sites determined in step (a) and the transit time calculated in step (c) using a processor.

30. The method of claim 29 wherein the arterial pulse data is obtained at two recording sites during at least one respiratory cycle.

31. The method of claim 30 further comprising calculating the pulse wave velocity from the measured distance between the first and second recording sites and the transit time delay of the proximal and distal waveforms.

32. A method for determining aortic pulse pressure in a patient, comprising the steps of:

a) determining aortic pulse wave velocity between a first recording site on a carotid artery of the patient and a second recording site on a femoral artery of the patient;

b) determining brachial pulse wave velocity between a first recording site on the carotid artery of the patient and a third recording site on a brachial artery of the patient;

c) measuring brachial pulse pressure; and

d) extracting the aortic pulse pressure from the aortic and brachial pulse wave velocities, and from the measured brachial pulse pressure, wherein the aortic pulse pressure P_a is determined using the relation;

33. A method for assessing cardiovascular function in a patient comprising the steps of:

applying a transducer to each of a proximal recording site and at least one distal recording site over the patient'"'"'s arterial system;

simultaneously recording an arterial pulse in wave form at the proximal recording site and at least one of the distal recording sites;

calculating transit time of the arterial pulse waveform between the proximal recording site and at least one of the distal recording sites comprising the steps of;

identifying a segment on an initial upstroke of the proximal waveform recorded at the proximal recording site;

identifying a segment on an initial upstroke of the at least one distal recording sites corresponding to the segment identified on the proximal waveform;

determining the transit time from a time delay between the segment identified on the proximal waveform and the corresponding segment identified on the distal waveform;

determining a distance between the proximal recording site and the at least one distal recording site;

calculating velocity of the pulse wave from the proximal recording site to at least one distal recording site from the determined transit time and the determined distance between the proximal recording site and the distal recording site; and

comparing the pulse wave velocity of the patient to a reference value, wherein a difference between the pulse wave velocity in the patient and the reference value is indicative of abnormal patient cardiovascular function.

34. The method according to claim 33 wherein the initial upstroke of the waveform comprises a time at which a derivative of the recording at the proximal recording site or the distal recording site is maximal.

35. The method according to claim 33 wherein identification of the initial upstroke in the distal waveform comprises searching in the distal recording for a moment when a coefficient of correlation is maximal when comparing corresponding areas around the initial upstroke of the proximal waveform and the initial upstroke of the-distal waveform.

36. The method according to claim 35 wherein the correlation coefficient is linear.

37. A method for determining central aortic pulse pressure of a patient comprising the steps of:

calculating central aortic hemodynamic behavior velocity between a recording site on a carotid artery and a recording site on a femoral artery;

calculating peripheral brachial hemodynamic behavior velocity between a recording site on the carotid artery and a recording site on a brachial artery;

measuring brachial pulse pressure; and

calculating the central aortic pulse pressure from the calculated aortic hemodynamic behavior velocity, the calculated brachial hemodynamic behavior velocity, and the brachial pulse pressure.