Methods and apparatus for R-wave detection

• US 5,984,954 A
• Filed: 10/01/1997
• Issued: 11/16/1999
• Est. Priority Date: 10/01/1997
• Status: Expired due to Fees

• Current Assignee: Boston Medical Technologies Incorporated
• Original Assignee: Boston Medical Technologies Incorporated
• Inventors: Cohen, Alan M.
• Primary Examiner(s): Jastrzab, Jeffrey R.
• Application Number:
  US08/940,396
• Time in Patent Office: 776 Days
• Field of Search: 600/513, 600/509, 600/521
• US Class Current: 600/521
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval

Abstract

Apparatus and methods for determining the precise times of occurrence of R-waves in an ECG signal of a patient. Samples of the patient'"'"'s ECG signal are accumulated and an ECG window comprising a predetermined number of the samples is defined. In accordance with one embodiment of the invention, the patient'"'"'s blood pressure signal is processed to detect systoles and the ECG window has a predetermined time relationship to detected systoles. In accordance with an alternative embodiment, the ECG signal is first processed to approximate the times of occurrence of R-waves and the ECG window is defined to have a predetermined time relationship to the approximated R-wave times. ECG signal samples within the ECG window are processed to determine a maximum and the time of occurrence of the maximum is stored as the time of an R-wave event.

Claims

1. A method of detecting the time of occurrence of the peak of an R-wave of an ECG signal of a patient, comprising the steps of:

storing the ECG signal of the patient;

approximating the time of occurrence of the peak of the R-wave in response to the stored ECG signal; and

determining the precise time of occurrence of the peak of the R-wave in response to the approximated time of occurrence of the peak of the R-wave.

2. The method of claim 1 wherein the approximating step includes:

comparing samples of the stored ECG signal within a first window to a threshold level; and

storing the time of occurrence of a sample exceeding said threshold level as the approximate time of occurrence of the peak of the R-wave.

3. The method of claim 2 further comprising the step of determining the threshold level by computing a percentage of the average peak values of samples of the stored ECG signal.

4. The method of claim 2 wherein the determining step includes:

searching a second window of the stored ECG signal preceding the first window for a maximum; and

storing the time of the maximum as the precise time of occurrence of the peak of the R-wave.

5. Apparatus for detecting the time of occurrence of the peak of an R-wave of an ECG signal of a patient comprising:

a memory for storing the ECG signal of the patient; and

a processor responsive to the stored ECG signal for approximating the time of occurrence of the peak of the R-wave and for determining the precise time of occurrence of the peak of the R-wave in response to the approximate time of occurrence of the peak of the R-wave.

6. The apparatus of claim 5 wherein the processor includes a first processor portion for approximating the time of occurrence of the peak of the R-wave in response to the stored ECG signal and a second processor portion for determining the precise time of occurrence of the peak of the R-wave in response to the approximate time of occurrence of the peak of the R-wave and the stored ECG signal.

7. The apparatus of claim 6 wherein the first processor portion includes:

a detector for detecting the time of occurrence of a sample of the stored ECG signal occurring within a first window of the stored ECG signal exceeding a threshold level; and

a storage mechanism for storing the the time of occurrence of the sample exceeding the threshold level in the memory as an approximate time of occurrence of the peak of the R-wave.

8. The apparatus of claim 7 wherein the second processor portion includes a detector for detecting a maximum of the stored ECG signal occurring during a second window of the stored ECG window preceding the first window, wherein the time of the maximum is stored in the memory as a precise time of occurrence of the peak of the R-wave.

9. A method of detecting the time of occurrence of the peak of an R-wave of an ECG signal of a patient, comprising the steps of:

accumulating a plurality of samples of the ECG signal of the patient;

defining an ECG window comprising a predetermined number of the accumulated samples of the ECG signal;

processing each sample comprising the ECG window to determine a maximum within the ECG window; and

storing the time of occurrence of the maximum as the time of occurrence of the peak of the R-wave.

10. The method of claim 9 further comprising the steps of:

accumulating a plurality of samples of a blood pressure signal of the patient;

defining a systole window comprising a predetermined number of the accumulated samples of the blood pressure signal; and

processing each sample comprising the systole window to determine the time of occurrence of a systole, wherein the ECG window defining step includes defining the ECG window to have a predetermined time relationship to the time of occurrence of the systole.

11. The method of claim 9 further comprising the step of approximating the time of occurrence of the peak of the R-wave and the ECG window defining step includes defining the ECG window to have a predetermined time relationship to the approximate time of occurrence of the peak of the R-wave.

12. A method of detecting times of occurrence of a plurality of R-waves of an ECG signal of a patient, comprising the steps of:

(a) storing the ECG signal of a patient;

(b) approximating the times of occurrence of the R-waves in response to the stored ECG signal, comprising the steps of;

(i) comparing samples of the stored ECG signal within a first window to a threshold level; and

(ii) storing the time of occurrence of a sample exceeding said threshold level as an approximate R-wave time; and

(c) determining the precise times of occurrence of the R-waves in response to the approximated times of the R-waves, comprising the steps of;

(i) searching a second window of the stored ECG signal preceding the first window for a maximum; and

(ii) storing the time of the maximum as the precise R-wave time.

13. Apparatus for detecting times of occurrence of a plurality of R-waves of an ECG signal of a patient comprising:

(a) a memory for storing the ECG signal of the patient; and

(b) a processor responsive to the stored ECG signal for approximating the times of occurrence of the R-waves and for determining the precise times of occurrence of the R-waves in response to the approximate times of the R-waves, said processor including a first processor portion for approximating the times of occurrence of the R-waves in response to the stored ECG signal and a second processor portion for determining the precise times of the R-waves in response to the approximate R-wave times and the stored ECG signal, said first processor portion including;

(i) a detector for detecting the time of occurrence of a sample of the stored ECG signal occurring within a first window of the stored ECG signal exceeding a threshold level; and

(ii) a storage mechanism for storing the time of occurrence of the sample exceeding the threshold level in the memory as an approximate R-wave time; and

said second processor portion including a detector for detecting a maximum of the stored ECG signal occurring during a second window of the stored ECG window preceding the first window, wherein the time of the maximum is stored in the memory as a precise R-wave time.