The present invention relates to a method for determining R peaks of electrocardiogram (ECG/EKG).
Electrocardiogram (ECG/EKG) is mostly used for monitoring electrical activity of the heart. It is considered to be non-invasive and can provide immediate results. Through the ECG/EKG, some heart diseases may be found.
Since various patterns of ECG signals may be obtained in different cardiac diseases, for example, two R waves are generated in right bundle branch block (RBBB) case, and T wave with high amplitude voltage and low slope in ST-segment elevation myocardial infarction (STEMI) case, it is difficult to find or locate the position of the R peaks of the ECG signal. Also, in a vibration environment, the detected ECG signal may be uneven, leading to hardly find or locate the position of the R peaks of the ECG signal.
Some approaches are proposed for finding the position of the R peaks, such as using complex wavelet to calculate multiple resolution feature of ECG signal to determine R peak, using first or second derivative differentiation to acquire the ECG variation and locate the position of the R peak, or using machine learning.
However, the wavelet-based approach needs multiple frequency conversions, resulting in highly complex calculation; the deep machine learning approach needs big data base as training set, and data base with high quality training set is not easy to collect, thereby complicating the approach; and the approach using the first or second derivative differentiation is not easy to accurately detect the R peaks of waveforms with large ripple or large shape variance, leading to affect the accuracy of automated diagnosis. Therefore, providing a simple method for determining the R peaks is a subject in the related field.
According to an embodiment, a method for determining R peaks of an electrocardiogram (ECG/EKG) is provided. First, an ECG/EKG complex is provided and followed by obtaining a maximum peak of the ECG/EKG complex. Later, a half of a largest voltage of the maximum peak as a threshold voltage is obtained, and then, an R peak number estimating process is performed to obtain an estimated number of all R peaks of the ECG/EKG complex and a plurality of peaks of the ECG/EKG complex with voltages higher than the threshold voltage. Next, whether a number of the plurality of peaks is equal to the estimated number of the all R peaks is determined. When the number of the plurality of peaks is equal to the estimated number of the all R peaks, the plurality of peaks are regarded as the all R peaks.
The present invention provides a method for automatically determining R peaks of ECG/EKG, in which the method utilizes the characteristic of beating cycle of heart that doesn't change suddenly as well as similar adjacent R peaks and includes auto-adjusting the threshold voltage the ECG/EKG complex, so the number of the R peaks can be easily and accurately found, thereby locating the R peaks. Also, the method doesn't need complicated calculation of the wavelet-based approach and is easily implemented in the portable device, also providing power saving function because of simple calculation. Furthermore, the method also doesn't require pre-annotating the ECG/EKG.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
In this embodiment, the ECG/EKG system 12 may include a digital signal processing unit 14 for determining the R peaks according to the following determining methods. For example, the digital signal processing unit 14 may include a pattern recognition unit 141 for determining PQRST complex waveforms that may include the plural R peaks. One of the PQRST complex waveforms may be one ECG cardiac cycle of the signal of any one of 12 leads, for example one ECG cardiac cycle of lead V2 or lead V3, but not limited thereto. One normal PQRST complex waveform may for example include one P wave representing the depolarization of the atria, one QRS complex representing the depolarization of the ventricles, and one T wave representing repolarization of ventricle, thereby for example including P, Q, R, S, and T points. In some embodiments, the ECG/EKG electrodes may collect analog ECG/EKG signals. In such situation, the ECG/EKG system 1 may further include an analog signal processing unit 16 and an A/D converting unit 18 for processing the analog ECG/EKG signal into a digital ECG/EKG signal for further R peaks searching. In some embodiments, the analog signal processing unit 16 may optionally include filter, amplifier, level shifter or rectifier, but not limited thereto. After the R peaks are determined, the PQRST complex waveforms including the R peaks may be further analyzed by the digital signal processing unit 14 (e.g. the pattern recognition unit 141) for recognizing the pattern of the PQRST complex waveform and extracting its feature (e.g. the J point). Accordingly, doctors, patients, or AI data analytics may be assisted by the processed data to have further clinical decision support.
In some embodiments, the ECG/EKG system 12 may further include an input/output unit 20, in which the input/output unit 20 may for example be a display panel or printer for showing the ECG/EKG to assist doctor to make a diagnosis.
In some embodiments, the ECG/EKG electrodes may collect digital signal and thus the digital ECG/EKG signal is transmitted to the digital signal processing unit 14 directly. The following method for determining R peaks is not limited to be applied to the digital signal processing unit 14 of the above-mentioned system 1.
In step S506, a half of the largest voltage VT1 of the maximum peak MPK (such as an voltage VT2) is calculated and defined as a threshold voltage for example by the digital signal processing unit. In step S508, an R peak number estimating step is performed to obtain an estimated number of all R peaks (N) of the ECG/EKG complex 100 and a plurality of peaks PK of the ECG/EKG complex 100 with voltages greater than the threshold voltage (e.g. the voltage VT2), in which the maximum peak MPK is one of the peaks PK. For example, the peaks PK can be found by searching peak points of the ECG/EKG complex that have the voltages greater than the half of the largest voltage VT1.
where sd is the standard deviation, n is the number of the peaks, x1, x2, . . . , xn are the voltages of the peaks PK, and x is the average of the voltages of the peaks PK. In step S608, an average of the remaining time intervals TI is calculated and obtained. In step S610, the estimated number of R peaks (N) is evaluated and obtained according to the average of the remaining time intervals TI and the duration of the ECG/EKG complex 100. For example, the estimated number of R peaks (N) is obtained by dividing the duration by the average of the remaining time intervals TI. The average may be for example a mean, a median or a mode of the remaining time intervals TI, but not limited thereto.
In step S510, after the estimated number of the R peaks (N) and the number of the peaks PK (n) are obtained, whether the number of the peaks PK (n) is equal to the estimated number of the R peaks (N) is determined by the digital signal processing unit. When the number of the peaks PK (n) is equal to the estimated number of the R peaks (N), the method proceeds to step S512, in which the peaks PK are regarded as the R peaks. Accordingly, all the R peaks can be found, and the method is ended.
When the number of the peaks PK (n) is not equal to the estimated number of the R peaks (N), the method proceeds to step S514 and includes increasing or decreasing the threshold voltage by a predetermined voltage to be another threshold voltage. For example, the threshold voltage may be increased or decreased by the digital signal processing unit. The predetermined voltage may be preset or stored in the digital signal processing unit. Then, the method returns to step S508, and the R peak number estimating process is performed again to find the peaks PK based on the another threshold voltage until the estimated number of the R peaks is equal to the number of the found peaks PK. Specifically, when the number of the peaks PK (n) is less than the estimated number of the R peaks (N), the threshold voltage is decreased to another threshold voltage, and the R peak number estimating process is performed again. On the other hands, when the number of the peaks PK (n) is greater than the estimated number of the R peaks (N), the threshold voltage is increased to another threshold voltage, and the R peak number estimating process is performed again.
It is noted that since beating cycle of heart doesn't change suddenly, the time intervals TI between the R peaks are almost the same. Also, because voltages of the adjacent R peaks are similar and large enough, through adjusting the threshold voltage, the peaks can be found, and then, the time intervals TI can be estimated. For this reason, through the loop of adjusting the threshold voltage, the number of the R peaks can be easily and accurately found, thereby locating the R peaks.
As mentioned above, in the method for determining R peaks of the present invention, since the calculation for determining the R peaks is simple and easy, no complicated calculation of the wavelet-based approach is required, and thus, the method is easily implemented in the portable device. Also, the method may further achieve energy saving effect because of simple calculation and/or may not require pre-annotating the ECG/EKG.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
This application claims the benefit of U.S. Provisional Application Ser. No. 62/888,556, filed Aug. 19, 2019, the contents of which are hereby incorporated by reference in their entirety.
Number | Date | Country | |
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62888556 | Aug 2019 | US |