**5. Application in chronic kidney disease**

of the difference between the (WT-based) automatic and the (CSE) manual (annotated) location of those characteristic points. The results for that difference are within the tolerance limits

Also, the algorithm has been tested on 15 recordings from MITDB included in the QTDB [24]. Within each record of two channels, between 30 and 100 representative beats were manually annotated by cardiologists, who identified among other characteristic points of ECG waves, Qi of the QRS-complex and Te of the T-wave. Channel 1 was used in most recordings, in case of ECG distorted, channel 2 was used. **Table 5** shows the mean (m) and standard deviation (sd) of the differences between the manual measurements (C1) and automatic measurements (WT) of Qi and Te for each record. The results for the differences between WT and C1 are within the tolerances for deviations with respect to the measurements made by the CSE

**Figure 15** shows some ECG excerpts of records with different T wave morphologies from QTDB with the manual annotations (square symbol) and the automatic detections (star symbol). It can be seen that Qi and Te are well determined by the algorithm, and its accuracy is

**Figure 15.** Automatic detections (star) and manual annotations (square) of Qi and Te with different types of morphologies of QRS complex and T wave in patterns of two beats of four records from QTDB. (a) rS positive T wave, (b) qRs biphasic

accepted by the CSE experts, as shown in the last row of **Table 4** [32].

experts, as shown in the last row of **Table 5** [32].

40 Topics in Splines and Applications

T wave, (c) Rs biphasic T wave and (d) qR negative T wave.

comparable to a manual measurement of human experts.

The QTd algorithm was applied in two studies. In the first study, QTd was evaluated in normal subjects and patients with CKD. In the second study, QTd was analyzed in patients with CKD before, during and after the HD treatment.

## **5.1. QTd analysis in normal subjects and patients with CKD**

In this study, 14 ECG recordings belonging to the PTBDB were used [26, 27], where the three quasi-orthogonal leads DI, aVF and V2 have been analyzed to obtain QTd. This database includes records of healthy people and patients with different pathologies. The study group was of seven normal subjects (two women and five men, age 66 ± 3.6 years) and seven renal insufficiency patients (three women and four men, age 70 ± 4.5 years). QTd corresponding to both groups was compared by the Wilcoxon rank sum test, where *p* < 0.05 was considered statistically significant.

**Table 6** shows QTd and HR in both groups. Difference in HR in both groups is not significant and therefore HR influence is similar in both groups [(67.7 ± 9) beats/min vs. (70.8 ± 12) beats/ min, *p* = 0.53]. QTd was significantly larger in patients with CKD than in normal subjects [(67.7 ± 28) ms vs. (21.4 ± 12), *p* = 0.0041]. The results obtained showed that the algorithm is effective to differentiate both groups.

### **5.2. QTd analysis in patients with CKD before, during and after hemodialysis**

In this study, four ECG records of patients with CKD in the stage referred to as kidney failure or ESRD of the THEWDB [28], before (pre-HD), during and after (post-HD) HD session were used. For each patient, the three quasi-orthogonal leads DI, aVF and V2 have been analyzed to obtain QTd in a period of 10 h, in which pre-HD, HD and post-HD periods correspond to


QTd in ms; HR in beats/min; m, mean; sd, standard deviation; *p* value is from Wilcoxon rank sum test.

**Table 6.** QTd and HR in seven normal subjects and seven CKD patients.

This new algorithm is based on the multilead generalization of a previous algorithm for single-lead detection of characteristic points of the QRS complex and T wave. It includes the identification of more types of morphologies of these waves, which are common in the analysis of several ECG leads and heart diseases. To evaluate its performance, ECG recordings of standard annotated databases MIT-BIH, QTDB and CSEDB were used. The results showed that the developed algorithm provides a reliable and accurate QRS detection and delineation of Qi and Te, with standard deviation of the errors within the tolerance limits for variations

An Algorithm Based on the Continuous Wavelet Transform with Splines for the Automatic…

http://dx.doi.org/10.5772/intechopen.74864

43

The QTd algorithm was applied in two studies. In the first one, QTd was evaluated as a discriminator of patients with CKD from normal subjects. The results showed that QTd was significantly larger in CKD patients than in normal subjects, which agrees with similar studies. In the second study, QTd was analyzed in four patients with CKD before, during and after the HD treatment. The results showed that all the patients have an increase of QTd during HD and post-HD, which has been associated with malign ventricular arrhythmias and sudden death in previous studies. Future applications of this algorithm will focus on to evaluate dispersion in other ECG ventricular activity intervals like JT (from S wave end to T wave end) and Tpe (from T wave peak to T wave end), in order to determine whether they improve the identification of CKD

patients with risk of malign ventricular arrhythmias compared with QT dispersion.

Bioelectronics Section, Department of Electrical Engineering, Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav), Mexico City, Mexico

[1] World Health Organization (WHO). Cardiovascular Diseases (CVDs) [Internet]. 2017- 05. Available from: http://www.who.int/mediacentre/factsheets/fs317/en/ [Accessed:

[2] Plonsey R. Electrocardiography. In: Webster JG, editor. Electrocardiography. New York:

[3] Instituto Nacional de Estadística y Geografía (INEGI). Defunciones generales por residencia habitual del fallecido y causa de la defunción (LISTA 1, CIE-10) según mes de ocurrencia, 2015 [Internet]. [Updated: 2016-11-30]. Available from: http://www. inegi.org.mx/est/contenidos/proyectos/registros/vitales/mortalidad/tabulados/def04.

with respect to the measurements made by different experts.

María de Lourdes Corzo-Cuesta and Carlos Alvarado-Serrano\*

\*Address all correspondence to: calvarad@cinvestav.mx

John Wiley & Sons; 1988. pp. 1017-1040

asp?t=13&c=11816 [Accessed: July 24, 2017]

**Author details**

**References**

July 25, 2017]

**Figure 16.** Dynamics of QTd of four CKD patients averaged every 15 min in pre-HD, HD and post-HD periods. (a) Patient 1013, (b) Patient 1030, (c) Patient 1050 and (d) Patient 1059.

the hours 1, 2–6 and 7–10, respectively. **Figure 16** shows the dynamics of QTd averaged every 15 min in a period of 10 h of the four CKD patients. It is observed that all the patients have an increase of QTd during HD and post-HD, which has been associated with malign ventricular arrhythmias and sudden death [6, 12].
