Electrocardiogram Delineation in a Wistar Rat Experimental Model

Abstract

Background and objectives: The extensive use of electrocardiogram (ECG) recordings during experimental protocols using small rodents requires an automatic delineation technique in the ECG with high performance. It has been shown that the wavelet transform (WT) based ECG delineator is a suitable tool to delineate electrocardiographic waveforms. The aim of this work is to implement and evaluate the ECG waves delineation in Wistar rats applying WT. We also describe the ECG signal of the Wistar rats giving the characteristics of its spectrum among other useful information.

Methods: We evaluated a delineator based on WT in a Wistar rat electrocardiograms database which was annotated manually by experienced observers.

Results: The delineation showed an "overall performance" such as sensitivity and a positive predictive value of 99.2% and 83.9% for P-wave, 100% and 99.9% for QRS complex, and 100% and 99.8% for T-wave, respectively. We also compared temporal analysis based ECG delineator with the WT based ECG delineator in RR interval, QRS duration, QT interval, and T-wave peak-to-end duration. The results showed that WT outperforms the temporal delineation technique in all parameters analyzed.

Conclusions: Finally, we propose a WT based ECG delineator as a methodology to implement in a wide diversity of experimental ECG analyses using Wistar rats.

Figure 1

ECG beats delineation from WR_DB. In (a), we can observe the QRS complex with its WT at scales 2² and 2³ and the peak and QRS boundaries obtained by the algorithm proposed. The npre and post positions were located in scale 2², while nfirst was located in scale 2³. In (b), we can see the P-wave and T-wave with their WT scales 2⁴ and 2⁵ and marks of peaks, onset, and end of characteristics ECG points. The npost, last, and minT positions were located in scale 2⁴, while nlast was located in scale 2⁵.

Figure 2

Representative power spectrum of ECG in human beings (a) and ECG in Wistar rats (b). The location of spectral contents in the P-wave, the QRS complex, and the T-wave can be observed.

Figure 3

Box and whisker plots showing the mean (a) and standard deviation (b) values for different ECG parameters in Wistar rats. The ECG parameters measured were the RR interval (RR), QRS duration (QRS), QT interval duration (QT), and T-wave peak-to-end duration (TPE). The temporal analysis based ECG delineator (TA_D) was represented with clear boxes and the wavelet transform based ECG delineator (WT_D) was represented with dark boxes. ^∗p < 0.05, ^†p < 0.001, and ^‡p < 0.0001 indicate statistically significant differences of ECG parameters between TA_D and WT_D. NS: nonstatistically significant differences between both groups.