Signal averaged ECG in patients with early repolarization

Abstract Background Early repolarization (ER) pattern is diagnosed when the J‐point is elevated on the patient's electrocardiogram. The aim of this study was to evaluate signal‐averaged electrocardiography (SAECG) in patients with ER pattern. Methods Subjects were divided into three groups: 1‐patients with normal ECG pattern (control group); 2‐patients with J‐point elevation in the inferior leads; and 3‐patients with J‐point elevation in non‐inferior leads. Results The mean filtered QRS duration in groups with J‐point elevation in inferior leads and non‐inferior leads and in the control, was 86.4 ± 23.4 msec, 84.8 ± 26.6 msec, and 85.8 ± 24.8 msec, respectively, indicating no significant difference across the three groups. The mean duration of terminal QRS < 40µV was 21.2 ± 4.2 msec, 22.8 ± 4.6 msec, and 23.1 ± 4.5 msec in the mentioned groups, respectively, without a significant difference between the groups. Additionally, the mean root‐mean‐square voltage of terminal 40 msec was 34.5 ± 8.3 µV, 35.3 ± 8.6µV, and 35.7 ± 9.2 µV in patients with increased J‐point in inferior leads, non‐inferior leads, and the control group, respectively, showing no difference between the groups. Conclusion In conclusion, we found that parameters in SAECG did not have any significant difference between patients with ER pattern and healthy individuals. Moreover, we concluded that SAECG cannot distinguish the patients with elevated J‐point in inferior leads from non‐inferior leads. Overall, SAECG does not appear to be a reliable diagnostic tool for the assessment of ER pattern.

signals averaged ECG (SAECG) has been developed over the recent years, which is a modality to evaluate and detect the occult impairment of ventricular activation. [5][6][7][8] The aim of this study was to evaluate the SAECG in patients with ER pattern and detect any possible relation between the SAECG parameters and ER pattern.

| Study population
A total of 38 consecutive patients (age 33.1 ± 7.7 years) under follow-up for ER and 20 healthy male subjects (age 28.3 ± 6.8 years) were included in the study. All patients underwent a 12-lead ECG and transthoracic echocardiography. Early repolarization pattern is diagnosed on the surface ECG by the presence of J-point elevation ≥1 mm in ≥2 contiguous inferior and/or lateral leads of a standard 12-lead ECG. This study received approval from the University Institutional Review Board and written informed consent was obtained from the subjects.

| Early repolarization syndrome
Early repolarization syndrome is diagnosed by the presence of J-point elevation ≥1 mm in ≥2 contiguous inferior and/or lateral leads of a standard 12-lead ECG in a patient resuscitated from otherwise unexplained ventricular fibrillation/ polymorphic ventricular tachycardia.

Duration of low amplitude signal (LAS40).
Abnormalities were detected if the filtered QRS complex was more than 114 ms, the square of the terminal signal was lower than 20 µV or a low amplitude signal longer than 38 ms Patients were considered as having late potentials (LPs) if they had abnormalities in at least two SAECG indices.

| Exclusion criteria
Patients with the following criteria were excluded from the study: history of coronary artery disease, abnormal LV systolic function (EF < 50%), significant valvular heart disease, bundle branch block (QRS > 120 msec), and patients who use anti-arrhythmic drugs.

| Statistical analysis
Continuous data were presented as mean ± standard deviation.
Normality of data was analyzed using the Kolmogorov-Smirnoff test.
The one-way analysis of variance (ANOVA) was used to determine whether there are any statistically significant differences between the means of the three groups. P values less than .05 were considered statistically significant. For the statistical analysis, the statistical software SPSS version 13 for windows (SPSS Inc, Chicago, IL) was used.  and patients with J-point elevation (Tables 1 and 2). The root-meansquare voltage of the terminal 40 msec was also not significantly different between the patients with J-point elevation in inferior leads (34.5 ± 8.3 µV), the ones with J-point elevation in non-inferior leads (35.3 ± 8.6µV), and the control group (35.7 ± 9.2 µV) (Tables 1 and 2).

| J-Wave amplitude and SAECG parameters
Patients were divided into two groups according to J-wave amplitude: • Group-1: Patients with J-wave amplitude <0.2 mV, • Group-2: Patients with J-wave amplitude ≥0.2 mV Table 4 shows SAECG parameters in the two groups (according to the J-wave amplitude). There were no significant differences between SAECG parameters and J-wave amplitude.
higher risk of ventricular dysfunction and reentrant ventricular tachyarrhythmia and hence, detecting the patients with a predisposition toward SCD. 15 In a study by Tahara et al 16 the filtered QRS duration was measured in SAECG in patients with ventricular dyssynchrony.
The results suggested that filtered QRS duration is a reliable measure in SAECG and it is related to ventricular dyssynchrony. As a result, one can conclude that SAECG can be considered as a tool in assessing conditions with ventricular dysfunction.
In this study we intended to measure SAECG parameters including QRS complex duration, duration of terminal QRS with <40 micro voltages, and root-mean-square voltage of the terminal 40 msec using a 12-lead resting ECG, which is the gold standard and the most reliable tool in ECG monitoring, to find any possible association between ER pattern and SAECG markers. Notably, none of the aforementioned markers in SAECG showed any significant difference between patients with an ER pattern and control group.

| CON CLUS ION
In conclusion, we found that parameters in SAECG including filtered QRS duration according to millisecond, duration of terminal QRS <40 micro voltages, the root-mean-square voltage of terminal 40 milliseconds did not have any significant difference between patients with ER pattern and healthy individuals. Moreover, we concluded that SAECG cannot distinguish the patients with elevated J-point in inferior leads from non-inferior leads. Overall, SAECG does not appear to be a reliable diagnostic tool for the assessment of ER pattern.

CO N FLI C T O F I NTE R E S T
None.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data underlying this article will be shared at reasonable request to the corresponding author.