IJBEM, Vol. 5, No. 1, 2003

Effect of Age and Sex on Time Domain Signal-Averaged ECG in Normal Taiwanese

Chun-Chen Lin^a^d, Chih-Ming Chen^a, Ten-Fang Yang^bc, Ing-Fang Yang^c

^aDepartment of Electrical Engineering, National Taiwan University of Science and Technology, Taipei
^bGraduate Institute of Medical Information, Taipei Medical University, Taipei
^cDepartment of Internal Medicine (Cardiology and Nephrology), Jen-Chi General Hospital, Taipei
^dDepartment of Electrical Engineering, Chin-Min College, Miaoli, Taiwan

Correspondence: Ten-Fang Yang, Graduate Institute of Medical Information, Taipei Medical University, 250 Wu Hsing Street, Taipei 110, Taiwan. E-mail: tfy@tmu.edu.tw, phone +886-2-23776730 ext 111, fax +886-2-23411903

Abstract. Purpose of the present study was to evaluate the influence of age and sex on the time domain parameters of signal averaged electrocardiogram (SAECG) in normal Taiwanese. Four time domain parameters, namely, fQRSD, LAS40, last RMS40, first RMS40 were measured in this study. A significant difference was observed between the older age groups and younger groups, aged 17 to 29. The age correlates significantly with the decrease of fQRSD (r= , p=0.03) and first RMS40 (r= , p=0.003). Additionally, there exists non-neglectable differences between both sexes in fQRSD and first RMS40. The mean fQRSD of men was 8ms longer than that of women (p=0.0000007), while the mean first RMS40 of men was 21 microV larger than that of women (p=0.003). Therefore, the diagnostic criteria of time domain SAECG should be age and sex dependent.

Keywords: Age; SAECG; Time Domain Analysis; Gender Difference; Ventricular Late Potentials; Ventricular Tachycardia

1. Introduction

SAECG has been applied to detect the ventricular late potentials (VLPs) in high risk ventricular tachycardia (VT) patients with good negative predictive accuracy [Simson, 1981]. The prevalence of VLPs in normal population is reported to be from 0 to 7 % [Cain et al., 1996]. A previous study of time domain SAECGs recorded from 195 normal Caucasian has shown that the mean fQRSD of men was 10.2 ms greater than that of women. It was suggested that the upper limit of fQRSD should be adequately modified by gender [Yang and Macfarlane, 1994]. In this study, the age and sex influence on the time domain SAECG parameters in normal Taiwanese are evaluated.

2. Material and Methods

There were 105 normal Taiwanese (55 men and 50 woman, aged from 17 to 79 years old) recruited for this study (Table 1). SAECG with a bipolar, orthogonal X, Y and Z lead system were recorded using a commercially available Simens-Elema Megacart^® machine. The raw ECG data of 10 minutes was sampled at 2k Hz with 12-bit resolution and stored on hard disk for subsequent analysis. The methods of the time domain SAECG analysis was according to the recommendations of the 1991 Task Force [Breithardt et al., 1991]. Four parameters of the QRS vector magnitude were evaluated: (1) fQRSD, (2) LAS40, (3) last RMS40 [Breithardt et al., 1991], and the root mean square voltage of the first 40 ms (first RMS40) [Kienzle et al., 1988].

All statistical analysis was done with the Microsoft Excel^® software. The two sample Student’s t test was used for comparing means of two independent variables and F test was used for the variance comparisons. Statistical significance was defined as p < 0.05. The Pearson’s product moment correlation coefficient r was also determined.

Table 2. Age and sex distribution of the normal Taiwanese

Age	17~29	30~39	40~49	50+	Total
Men	43	6	3	3	55
Women	19	5	14	12	50
Total	62	11	17	15	105

Table 3. fQRSD and first RMS40 in each age group.

Age

17~29

30~39

40~49

50+

Total

fQRSD(ms)

Mean(SD)

93(8)

92(10)

87(7)^*

89(7)

91(8)

First RMS40

Mean(SD)

85(44)

58 (18)^*

60(21)^*

59(19)^**

74(38)

^* p<0.01, ^**p<0.001 compared to 17~29 age layer

2. Material and Methods

3. Results

Table 4. Normal ranges of time domain SAECG parameters.

		fQRSD (ms)	LAS40 (ms)	Last RMS40 (microV)	First RMS40 (microV)
Men	Mean(SD)	95 (8)^**	31 (8)	44 (27)	84 (46)^*
Men	Range(96th percentile)	78~109	16~51	13~126	32~194
Women	Mean(SD)	87 (7)	30 (7)	41 (26)	63 (22)
Women	Range(96th percentile)	72~99	19~44	13~115	31~121

^*p=0.003, ^**p=0.0000007 between sexes.

Figure 1. Cumulative distribution of filtered total QRS duration in normal Taiwanese.

The Pearson’s product moment correlation coefficients between age and fQRSD, LAS40, last RMS40, first RMS40 were (p=0.03), (p>0.05, NS), (NS) and (p=0.003) separately. Hence there were significantly negative correlations between age and fQRSD and first RMS40. Figure 1 shows that the upper 96th percentile for a normal fQRSD was 109 in men and 99 ms in women.

4. Discussion

Generally speaking, the effectiveness of time domain SAECG analysis was affected by several signal processing procedures, namely, signal averaging technique, filter type and the level of noise. In addition, age and sex has also been demonstrated to have influence on the analysis of SAECG. In 1991, Malik et al. reported that significant correlations were presented between age and time domain parameters in patients surviving myocardial infarction (MI). However, in normal Taiwanese, age and fQRSD correlated significantly, while a negative correlation was observed between age and first RMS40. In addition, significant differences of fQRSD and first RMS40 appeared in aged 17~29 group and aged 40~49 group. These variations might be originated from race difference and MI patient.

The mean fQRSD of men was 8 ms longer than women. This result was consistent with a previous study of the SAECGs in normal Caucasian [Yang and Macfarlane, 1994]. This study has shown that the mean first RMS40 of women was 21 microV significantly smaller than men. Kienzle et al. in 1988 reported that the first RMS40 in VT patients were smaller than normal people. This had been confirmed independently by Kulakowski et al. in 1992. Therefore, it is well demonstrated that the SAECG parameters are varied with age and sex differences. Hence the diagnostic criteria for the VLPs detection should be modified accordingly in practice.

Acknowledgements

The authors would like to thank the staffs and patients of Hemodialysis Unit at Jen-Chi General Hospital for their kind assistance and cooperation for this study.

References

Breithardt G, Cain ME, el-Sherif N, Flowers NC, Hombach V, Janse M, Simson MB, Steinbeck G. Standards for analysis of ventricular late potentials using high-resolution or signal-averaged electrocardiography: a statement by a task force committee of the European Society of Cardiology, the American Heart Association, and the American College of Cardiology. Journal of the American College of Cardiology, 17:999-1006, 1991.

Cain ME, Anderson JL, Arnsdorf MF, Mason JW, Scheinman MM, Waldo AI. Signal-Averaged Electrocardiography. Journal of the American College of Cardiology, 27:238-249, 1996.

Kienzle MG, Falcone RA, Simson MB. Alterations in the initial portion of the signal-averaged QRS complex in acute myocardial infarction with ventricular tachycardia. The American journal of cardiology, 61(1):99-103, 1988.

Kulakowski P, Marlik M, Poloniecki J, Bashir Y, Odemuyiwa W, Farrell T, Staunton A, Camm J. Frequency versus time domain analysis of signal-averaged electrocardiograms. II. Identification of Patients With Ventricular Tachycardia After Myocardial Infaction. Journal of the American College of Cardiology, 20:135-143,1992.

Malik M, Odemuyiwa O, Poloniecki J, Kulakowski P, Farrell T, Staunton A, Camm AJ. Age-related normal values of signal-averaged electrocardiographic variables after acute myocardial infarction. The American journal of cardiology, 68(5):440-445, 1991.

Simson MB. Use of signals in the terminal QRS complex to identify patients with ventricular tachycardia after myocardial infarction. Circulation, 64:235-242, 1981.

Yang TF, Macfarlane PW. New sex dependent normal limits of the signal averaged electrocardiogram. British heart journal, 72: 197-200, 1994.