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 Table of Contents  
Year : 2015  |  Volume : 12  |  Issue : 2  |  Page : 101-105

Prevalence and determinants of electrocardiographic abnormalities among staff of a tertiary institution in Southwest, Nigeria

1 Department of Internal Medicine, Cardiology Unit, LAUTECH Teaching Hospital; Department of Medicine, College of Health Sciences, Ladoke Akintola University of Technology, Ogbomosho, Oyo State, Nigeria
2 Department of Internal Medicine, Cardiology Unit, LAUTECH Teaching Hospital, Ogbomosho, Oyo State, Nigeria

Date of Web Publication30-Jul-2015

Correspondence Address:
Adeseye A Akintunde
P.O. Box 3238, Osogbo
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0189-7969.152004

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Background: Electrocardiogram (ECG) is a simple bedside investigation that can identify cardiovascular abnormalities among apparently normal individuals.
Objectives: To assess the prevalence and determinants of ECG abnormalities among staff of a tertiary institution (Ladoke Akintola University of Technology [LAUTECH]) in Southwest, Nigeria.
Materials and Methods: A total of 202 participants (47% men, 53% female) randomly selected staff of LAUTECH university was subjected to comprehensive medical examination, including body mass index, fasting lipid profile, ECG among others. ECG abnormalities were identified and related to potential determinants.
Results: The main ECG aberrations (prevalence %) are: left ventricular hypertrophy (LVH) (39.6%), QTc prolongation (20.3%), sinus tachycardia (7.9%), right ventricular hypertrophy (4.7%), conduction defects (6.4%), ectopic beats (3.9%). T-wave abnormalities (2.1%), arrhythmia (1.0%), ischemic heart disease (1.5%), Wolf-Parkinson-White pattern (1.0%) and 82.3% had normal axis while the remaining had some form of abnormal axis. Blood pressure variables were consistently associated with all ECG abnormalities.
Conclusion: ECG aberrations in this apparently normal population were dominated by conduction defects and LVH. This study emphasizes the necessity of regular cardiovascular assessment in apparently normal population in order to identify cardiovascular disease in its early stage and implement appropriate therapeutic and preventive strategies.

Keywords: Determinants, electrocardiography, prevalence, university staff

How to cite this article:
Akintunde AA, Akinlade OM, Opadijo OG. Prevalence and determinants of electrocardiographic abnormalities among staff of a tertiary institution in Southwest, Nigeria. Nig J Cardiol 2015;12:101-5

How to cite this URL:
Akintunde AA, Akinlade OM, Opadijo OG. Prevalence and determinants of electrocardiographic abnormalities among staff of a tertiary institution in Southwest, Nigeria. Nig J Cardiol [serial online] 2015 [cited 2023 Jun 8];12:101-5. Available from: https://www.nigjcardiol.org/text.asp?2015/12/2/101/152004

  Introduction Top

Cardiovascular disease (CVD) is a broad, all-encompassing term, a general diagnostic category consisting of diseases of the heart and circulatory (vascular) system. These diseases include coronary heart disease (CHD), stroke, peripheral artery disease, and rheumatic heart disease amongst others. CHD and stroke are the leading CVDs. In the second half of the 20 th century, CVDs became the dominant cause of global mortality and a major contributor to disease-related disability. [1],[2] The observed increase in CVD in developing countries may be due to a shift from nutritional deficiencies and infectious diseases as the major cause of death and disability to degenerative disorders; economic ascent of nations as they industrialize leading to increasing longevity, urbanization and lifestyle changes. [1]

Nigeria, being a strategically placed country in the West African sub-region is not left out of the scourge of noncommunicable diseases including hypertension and its modifiable risk factors as they are responsible for at least 20% of all deaths and constituting about 60% of medical wards hospital admissions in most tertiary health institutions. [2],[3]

An electrocardiogram (ECG) is widely used for monitoring. The resting ECG is the most widely used cardiovascular diagnostic test. Approximately, 75 million are performed each year in the United States alone, and probably twice that number around the world. [1] ECG changes appear early in the course of CVDs, and usually include alterations such as sinus tachycardia, QTc prolongation, QT dispersion, changes in heart rate variability, ST-T changes, and left ventricular hypertrophy (LVH). These changes and others, detected with the use of a resting ECG, often together with an exercise ECG, are used to detect silent ischemia, assess prognosis and predict future risk. [4]

Because the ECG is a noninvasive and relatively easy test to perform, it is used in series of investigations conducted as part of the annual clinical evaluation of symptomatic population around the world. [5],[6],[7] In recent times there has been increase in cardiovascular events including strokes, heart failure, ischemic heart disease and pulmonary hypertension among staff members of tertiary institution where the study was carried out, thus necessitating the need for this study.

This study was, therefore, aimed at identifying the pattern of major ECG abnormalities and their determinants among selected University workers in Ladoke Akintola University of Technology (LAUTECH), Ogbomosho, Nigeria. This will provide information that may be useful in the implementation of preventive strategies and also serve as a motivation for further investigations in this area.

  Materials and methods Top

The study was conducted among 202 workers of LAUTECH, Ogbomosho, a major town in Oyo state, Southwest of Nigeria. Only staffs comprising both teaching and nonteaching who had presented for the medical check-up were studied to find out the prevalence of ECG abnormality. They had all been active and found medically fit for their respective employment. The subjects who were symptomatic of chorionic villus sampling or respiratory disease were excluded as this study was focused only on healthy asymptomatic staff members.

The participants were randomly selected among academic and nonacademic staff of LAUTECH, Ogbomosho, Nigeria. The study was carried out between January and May 2014. The subjects were asked basic questions about their age and other sociodemographic data through a pretested structured questionnaire. The clinical evaluation and sample collection were carried out at the university health center. Prior notice and permission were obtained from the university senate. Ethical clearance was received from the ethical committee of LAUTECH teaching hospital, Ogbomosho. The study complied with the ethical declaration of Helsinki. Consent was obtained from all participants.

Blood pressure (BP) (mmHg) was measured on the right arm with the participant in a seated position, after 10 min' rest, with an Omron® Mx 2 basic electronic device (Omron Healthcare Co., Ltd., Kyoto, Japan) with the appropriate cuff size. The average of two measurements recorded 5 min apart was used in this study. Body weight (kg) was measured in light clothing, using a SECA® scale, and height (m) was measured with a standard stadiometer. The body mass index (BMI) for each patient was calculated as weight/height 2 (kg/m 2 ). The waist circumference (WC) (cm) was measured with a tape measure on the horizontal plane midway between the lowest rib margin and the upper edge of the iliac crest at mid expiration.

Dyslipidemia was defined as any one of these: Raised triglycerides level ≥1.7 mmol/L, reduced high density lipoprotein (HDL-cholesterol)-<1.03 mmol/L in males and <1.30 mmol/L in females, low density lipoprotein (LDL-cholesterol) level higher than 3.37 mmol/L and/or TC level ≥5.2 mmol/L (200 mg/dL). [16] Abnormal WC, waist-hip ratio (WHR) and BMI were taken as ≥94 cm in men and ≥80 cm in women, >0.90 for men and 0.85 for women, and ≥25 kg/m 2 across sexes respectively. [16]

A 12-lead resting ECG was done on all subjects using the Cardi Max Fx-7302® . All ECG tracings were centrally interpreted by the same investigator who is a cardiologist (axis deviation [AD]) and did not know the subjects' backgrounds. Significant ECG findings such as ST-segment elevation or depression, T-wave aberrations (inversion or tall T-wave), bundle branch block, LVH, right and left atrial enlargement (LAE), arrhythmias and other changes were noted.

Left ventricular hypertrophy was defined according to the presence of any of the three different criteria below:

  • Cornell voltage-duration product ([RaVL + SV3] × QRS complex duration) >2.623 mm × ms in men and >1.558.7 mm × ms in women. [15]
  • Cornell voltage (SV3 + RaVL >24 mm in women and 28 mm in men)
  • Sokolov-Lyon index (SV1 + RV5/6 >35 mm). Compared with echocardiography, the cut-off values for the Cornell voltage duration product gave the best sensitivity with a specificity of 95%. [15]

Electrocardiogram measurements were done with a ruler on the resting ECG tracings and were expressed as the average of three determinations on consecutive QRS complexes. R-wave amplitude in aVL and S-wave depth in V3 were measured as the distance (mm) from the isoelectric line of their zenith and nadir, respectively. QRS duration was measured from the beginning to the end of the QRS complex. QTc prolongation was defined as a QTc >450 ms in men and 460 ms in women.

The diagnosis of ischemic heart disease was made based on the American heart association criteria. [12] These criteria include ECG features of significant ST-segment depression, defined as ST-segment depression >1 mm in more than one lead and T-wave inversion. Myocardial infarction was defined as an ST-segment elevation (convex upwards) >0.08 s, associated with T-wave inversion in multiple leads, and reciprocal ST-segment depression in opposite leads.

Diagnostic criterion for right bundle branch block-QRS duration >120 ms, a secondary R-wave in V1/V2, wide slurred S-wave in lead I and V5/V6, ST-segment or T-wave, depression in V1-V2.

Diagnostic criterion for left bundle branch block (LBBB): QRS >120 ms, Broad R in I, V5/V6, Absence of Q in V5/V6.

Displacement of ST/T in opposite directions to the dominant deflection of the QRS.

Complex, Poor R-wave progression in chest leads, RS complex in V5/V6, left axis deviation (LAD). [15]

Statistical analysis

All the data were recorded and analyzed using the Statistical Package for Social Sciences software (SPSS Inc., Chicago, IL v16, USA). Continuous variables like age, systolic BP, diastolic BP, lipid profile, BMI, WC, and WHR are presented as mean ± standard deviation and compared across sexes while other categorical variables were expressed in frequencies and percentages with P < 0.05 taken as statistically significant. Pearson correlation was used to test for association between variables with significant P < 0.01.

  Results Top

A total of 202 subjects was included in this study with age ranging between 27 and 73 years (mean = 46.03 ± 7.94 years and 44.25 ± 7.64 years for males and females respectively). The females were more 107 (52.9%) versus 95 (47.1) and their ages were lower, though not significant, P = 0.090).

[Table 1] shows that of the demographic variables computed, only the height was significantly higher in males than in females (1.65 ± 0.06 vs. 1.58 ± 0.06; P < 0.001), all the other variables were higher in females than in males.
Table 1: Basic demographic data of the population (mean±SD)

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Among the subjects, a disproportionately higher number of females have both visceral obesity and low HDL-dyslipidemia as shown in [Table 2]. Eighty-five (79.4%) had abnormal WC as opposed to just 30 (31.6%) of the males. With regards to frequency of dyslipidemias, 57.9%, 70.1% and 58.9% of the females and 44.2%, 37.9% and 53.7% of males had high TC, low HDL, and high LDL respectively. Of these, only low HDL was significantly higher than that of males (P ≤ 0.001). This is shown in [Table 2].
Table 2: Compared the frequency of abnormal clinical and laboratory parameters between the male and female gender

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The distribution of ECG abnormalities was: T-wave aberrations (1.9%), LVH (42.5%), LAE (54.3%), right ventricular hypertrophy (9.6%), ischemic heart disease (13.6%), conduction defects (6.4%), QTc prolongation (20.3%) and ectopic beats (3.5%). Unlike QTc prolongation and ST-segment abnormality, the prevalence of major aberrations was similar in men and women [Table 3]. The distribution of subtypes of arrhythmia, conduction defects, and T-wave aberrations is shown in the table below. [Table 4] shows that none of the ECG parameters including axis, PR interval, QTc prolongation and PR interval were significant predictors of major cardiovascular risk factors among the study participants.
Table 3: Prevalence of ECG abnormalities

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Table 4: ECG patterns and cardiovascular predictors

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  Discussion Top

This study revealed a high prevalence of ECG abnormalities in this population. While some of these aberrations were benign, others were potential indicators of the presence of serious conditions such as ischemic heart disease or were associated with increased future risk of fatal and nonfatal cardiovascular events. The minimal use of preventive treatment for CVD in Nigerian population highlights the scope for improving cardiovascular health. Some aspects of ECG abnormalities, such as those relating to LVH, [8] ischemic heart disease [9] or QTc prolongation [10] have been investigated in a few studies, though in patients with diabetes in Africa. To the best of our knowledge, however, this study remains the most recent study that has investigated the full spectrum of resting ECG aberrations and potential determinants among university staffs in this part of the world.

Similar to the previous study in Tanzania, [8] we found a 64.1% prevalence of LVH in our study. Interestingly, BP variables were also the main determinants of LVH, with approximately similar range of effects. [8] It is possible that the prevalence of ECG-diagnosed cardiac ischemia is increasing 7 (3.5%) as seen in our study for at least two reasons: (1) In the absence of a correlation between ECG aberrations and clinical features, some of the observed ST-segment and T-wave changes could have been variants of normal ECGs, as previously described in blacks; [11] (2) some of the repolarization changes could have been secondary to hypertension.

The overall prevalence of QRS AD to left in this study was 10.5%/9.3% respectively in males and females, In a similar study Gupta et al. [13] had found the prevalence of LAD in 10.6/1000 population in rural India. The other ECG abnormalities like ventricular premature complex and LBBB should be further evaluated with tests like stress test, Thallium scan, Holter studies or coronary angiography. [14] However, due to limitations these were not performed as a part of this study and these personnel were referred to a higher center for further investigations.

In a cohort of black and white subjects with no known CVD who were participants of the Health, Aging, and Body Composition study (Health ABC study), the presence of major or minor ECG aberrations at baseline was associated with CHD risk during follow-up, independent of classical cardiovascular risk factors. [12] The findings of the Health ABC study suggest that the presence of ECG aberrations, including those used to diagnose cardiac ischemia in our study, should be given consideration as they may indicate an adverse underlying cardiovascular risk profile.

  Conclusion Top

Electrocardiogram aberrations are not uncommon among asymptomatic subjects especially in the tertiary institution where there is higher stress in coping with students' burden. While some may be benign, others are indicators of serious underlying conditions or high future risk for CVD. These aberrations have the potential to improve CVD risk stratification and the implementation of preventative strategies among Nigerian population.

Our findings have certain important implications for cardiovascular screening. The 12-lead ECG has been suggested as a relatively simple and inexpensive test to strengthen the limited diagnostic efficacy of the medical history and physical examination and indeed, this has been routine practice in many countries, in which a systematic screening program for preemployment is incorporated. The present study, however, defines certain limitations of the ECG in identifying CVD. However, normal ECGs were highly predictive of the absence of cardiovascular abnormalities, probably because of the low prevalence of CVD in our healthy study population.

The growing prevalence of serious ECG aberrations over time suggests the need for strategies to monitor such changes and their determinants through regular routine and comprehensive medical check-ups among staffs of tertiary institutions, so as to refine the cardiovascular preventative strategies in the country.

  References Top

World Health Organization. Atlas of Cardiovascular Diseases. Geneva: WHO; 2005. p. 3-19.  Back to cited text no. 1
Mensah GA. Ischaemic heart disease in Africa. Heart 2008;94:836-43.  Back to cited text no. 2
Dalal S, Beunza JJ, Volmink J, Adebamowo C, Bajunirwe F, Njelekela M, et al. Non-communicable diseases in sub-Saharan Africa: What we know now. Int J Epidemiol 2011;40:885-901.  Back to cited text no. 3
World Health Organization. Facing the Facts: The Impact of Chronic Disease in Nigeria. Geneva: WHO; 2005. Available from: http://www.who.int/chp/chronic_disease_report/en/. [Last accessed on 2011 Mar 12].  Back to cited text no. 4
Unachukwu CN, Agomuoh DI, Alasia DD. Pattern of non-communicable diseases among medical admissions in Port Harcourt, Nigeria. Niger J Clin Pract 2008;11:14-7.  Back to cited text no. 5
Whincup PH, Wannamethee G, Macfarlane PW, Walker M, Shaper AG. Resting electrocardiogram and risk of coronary heart disease in middle-aged British men. J Cardiovasc Risk 1995;2:533-43.  Back to cited text no. 6
Ashley EA, Raxwal VK, Froelicher VF. The prevalence and prognostic significance of electrocardiographic abnormalities. Curr Probl Cardiol 2000;25:1-72.  Back to cited text no. 7
Lutale JJ, Thordarson H, Gulam-Abbas Z, Vetvik K, Gerdts E. Prevalence and covariates of electrocardiographic left ventricular hypertrophy in diabetic patients in Tanzania. Cardiovasc J Afr 2008;19:8-14.  Back to cited text no. 8
Lester FT, Keen H. Macrovascular disease in middle-aged diabetic patients in Addis Ababa, Ethiopia. Diabetologia 1988;31:361-7.  Back to cited text no. 9
Odusan O, Familoni OB, Raimi TH. Correlates of cardiac autonomic neuropathy in Nigerian patients with type 2 diabetes mellitus. Afr J Med Med Sci 2008;37:315-20.  Back to cited text no. 10
Brink AJ. The normal electrocardiogram in the adult South African Bantu. S Afr J Lab Clin Med 1956;2:97-123.  Back to cited text no. 11
Auer R, Bauer DC, Marques-Vidal P, Butler J, Min LJ, Cornuz J, et al. Association of major and minor ECG abnormalities with coronary heart disease events. JAMA 2012;307:1497-505.  Back to cited text no. 12
Gupta R, Sharma S. Prevalence of asymptomatic electrocardiographic abnormalities in a rural population. J Assoc Physicians India. 1996;44:775-77.  Back to cited text no. 13
Hanne-Paparo N, Wendkos MH, Brunner D. T wave abnormalities in the electrocardiograms of top-ranking athletes without demonstrable organic heart disease. Am Heart J 1971;81:743-7.  Back to cited text no. 14
Norman JE Jr, Levy D. Improved electrocardiographic detection of echocardiographic left ventricular hypertrophy: Results of a correlated data base approach. J Am Coll Cardiol 1995;26:1022-9.  Back to cited text no. 15
National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report. Circulation 2002;106:3143-421.  Back to cited text no. 16


  [Table 1], [Table 2], [Table 3], [Table 4]

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