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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 15  |  Issue : 1  |  Page : 33-40

A comparative and correlation study of electrocardiographic and echocardiographic left ventricular parameters in hypertension


1 Department of Medicine, College of Medicine, University of Lagos, Idiaraba, Nigeria
2 Department of Medicine, University College Hospital, Ibadan, Nigeria

Date of Web Publication7-May-2018

Correspondence Address:
Dr. Oluseyi Adegoke
Department of Medicine, College of Medicine, University of Lagos, Lagos
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njc.njc_4_17

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  Abstract 


Background: Routine echocardiographic assessment of left ventricular (LV) size and function in hypertensive individuals is desirable, but in resource-challenged African countries where this may be impracticable it is important to identify patients who after electrocardiographic (ECG) evaluation would benefit from further evaluation with echocardiography.
Objective: To compare the echocardiographic parameters reflective of LV size and systolic function in hypertensive patients with normal ECG, LV hypertrophy (LVH) by voltage criteria only, and LVH with strain on electrocardiogram.
Subjects and Methods: A cross-sectional comparative study of echocardiographic LV size and systolic function in hypertensive participants with normal ECG (60 participants), LVH with strain (51 participants), and LVH by voltage criteria only (50 participants) on ECG, attending the Cardiology Clinic of a University Teaching Hospital in Lagos, Nigeria.
Results: ECG LVH with strain was associated with greater LVM index, higher prevalence of echocardiographic derived LVH, increased tendency toward hypertrophic LV geometric patterns, increased LV internal dimensions, LV systolic dysfunction, dilated left atrium and aortic root, as compared with ECG LVH by voltage criteria only and normal ECG in Nigerian hypertensive patients.
Conclusion: ECG LVH with strain identifies a group of hypertensive individuals who are at increased cardiovascular risk and would benefit from further evaluation by echocardiography. Where echocardiography may not be readily accessible, this ECG pattern may aid decision making on appropriate therapeutic interventions.

Keywords: Electrocardiographic strain pattern, left ventricular geometry, left ventricular hypertrophy, left ventricular systolic dysfunction


How to cite this article:
Adegoke O, Adebiyi AA. A comparative and correlation study of electrocardiographic and echocardiographic left ventricular parameters in hypertension. Nig J Cardiol 2018;15:33-40

How to cite this URL:
Adegoke O, Adebiyi AA. A comparative and correlation study of electrocardiographic and echocardiographic left ventricular parameters in hypertension. Nig J Cardiol [serial online] 2018 [cited 2018 Dec 11];15:33-40. Available from: http://www.nigjcardiol.org/text.asp?2018/15/1/33/231975




  Introduction Top


Left ventricular hypertrophy (LVH) in hypertension is associated with severe cardiovascular risk and poor prognosis, particularly in the black race.[1],[2] For effective assessment of the cardiovascular risk associated with LVH in hypertension, the severity of the increase in LV mass (LVM), the geometric pattern and the LV function, among others should be considered.[3] Echocardiography has emerged an objective tool for evaluating LV size and function in hypertension.[3],[4],[5] While it is desirable for all hypertensive patients to undergo echocardiography, resource constraints limiting access may make this impracticable in many African countries.

Electrocardiography (ECG) is more widely available as a routine investigation in individuals with hypertension.[6] Thus, it may be pertinent to identify patients who after ECG evaluation would benefit from further evaluation with echocardiography. There are several criteria for diagnosing LVH from the ECG. The commonly used ones include Sokolow–Lyon voltage criteria,[7] the strain pattern,[8] and a combination of the two.[9]

The connotations and prognostic importance of these criteria vary. When diagnosed by the strain pattern, ECG LVH is thought to carry a poorer prognosis.[10],[11] In one study, ECG strain pattern was associated with a 2.26-fold increased risk of cardiovascular event than when LVH was diagnosed by voltage criteria only. In that study, a 5-year cardiovascular mortality of 9.1% and 4.3% was reported in ECG strain pattern and LVH by voltage criteria only, respectively.[10] The presence of LVH with strain pattern on ECG is thought to represent the ECG abnormality with the greatest prognostic information for future cardiovascular events.[8],[12] In the Framingham heart study, ECG LVH with strain was associated with 3–15-fold increased risk of cardiovascular event with a 5-year mortality of 33% and 21% in men and women, respectively.[9] Reported explanations for the poorer prognosis include the association of the strain pattern with more severe increase in LVM and LV systolic dysfunction (LVSD).[8],[13] The strain pattern has also been associated with an increased tendency for the development of abnormal LV geometry,[3] though it has not been shown to predict any specific geometric pattern.[8],[14],[15],[16] The studies have shown that the presence of strain pattern on the ECG in hypertensive participants was associated with LVSD and an increased risk of developing or dying from congestive heart failure.[8],[13] While the presence of strain pattern on the ECG is more common in people of African decent,[8] most of the reported Caucasian studies had little indigenous black African representation.[3],[9],[13],[14]

This study, therefore, aims at comparing the echocardiographic parameters of LV size and systolic function in hypertensive patients with normal ECG, LVH by voltage criteria only, and LVH with strain on the electrocardiogram.

Study design

This was a cross-sectional comparative study conducted at the Cardiology clinic of Lagos University Teaching Hospital, Lagos, Nigeria. Ethical clearance was obtained from the Health Research Ethics Committee of the hospital, and informed consent was obtained from all the participants.


  Subjects and Methods Top


Participants were consecutive consenting hypertensive patients aged 18 years and above, attending the clinic. The participants selection procedure is as shown in [Figure 1].
Figure 1: Participants selection procedure

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Clinical evaluation

The consenting participants were further interviewed and underwent complete physical examinations. The parameters obtained include blood pressure, mean arterial pressure (MAP), body mass index (BMI), and body surface area (BSA). The case files were also reviewed to ascertain their clinical status and records. The participants included in the study must have had systemic blood pressure ≥140/90 mmHg on at least three different clinic visits, or with lower blood pressure if they had been on antihypertensive agents.[17] Participants, who had clinical features suggestive of heart failure or other cardiac diseases, renal failure, diabetes mellitus, other illnesses such as malaria, and drug use other than antihypertensive agents, were excluded from participating in the study. Participants that met the inclusion criteria at this stage proceeded to have their electrocardiograms recorded.

Electrocardiogram

A resting electrocardiogram (ECG) was recorded for each participant in supine position using a portable Seward model 9952 electrocardiogram machine with standard 12-lead electrodes in accordance with the recommendations of the American Heart Association.[18] The participants were then classified based on their ECG findings as follows: Group 1: LVH with strain; Group 2: LVH by voltage criteria; and Group 3: Normal.

LVH by voltage criteria was defined by the Sokolow–Lyon criteria.[7] LV strain pattern was defined as asymmetrical ST-segment depression ≥1 mm with asymmetrically inverted T-wave in leads I, aVL, V5, and V6.[8] LVH with strain was defined as simultaneous presence of the Sokolow–Lyon voltage criteria and the LV strain pattern.[9] Participants who met these criteria were further recruited and booked for echocardiographic study. Participants who had ECG features of bundle branch block or myocardial infarction were excluded from further participating in the study.

Echocardiographic studies

Two-dimensional-guided M-mode echocardiography with the use of Hewlett Packard Sono 2000 model echocardiographic machine and a 3.5MHz transthoracic transducer was performed with the participants in semi-decubitus position. Participants who had segmental wall motion abnormality were further excluded from the study. Measurements were made using the leading edge to leading edge method as recommended by the American Society of Echocardiography.[19] A minimum of three measurements were made and the average recorded. The measured parameters were LV internal diameter in diastole (LVIDD), LV internal diameter in systole (LVIDS), inter-ventricular septal wall thickness, posterior wall thickness (PWT), and E-point septal separation. LV end-systolic volume (LVESV) and LV end-diastolic volume (LVEDV) were estimated using Teichholz formula.[20]

LVM index (LVMI) was calculated using the formula published by Devereux et al.,[21] and was indexed to the allometric power of height. Relative wall thickness (RWT) was calculated by the formula: 2 (PWT)/LVIDD. ECG derived LVH (echo LVH) was considered present if LVMI was ≥49.2 g/m 2.7 in males or ≥46.7 g/m 2.7 in females.[22] Increased RWT was considered present when RWT was >43.[23]

Based on the value of RWT and the presence of echo LVH, LV geometric patterns were classified as Normal – if RWT was normal and there was no echo LVH; Concentric remodeling – if RWT was increased and there was no echo LVH; Eccentric hypertrophy – if RWT was normal and there was echo LVH; and Concentric hypertrophy – if RWT was increased and there was echo LVH.

Fractional Shortening (FS) was calculated using the formula: LVIDD – LVIDS/LVIDD × 100. Ejection fraction (EF) was calculated using the formula: ([LVEDV-LVESV]/[LVEDV]) × 100. LVSD was considered present if EF was <50%[24] and/or FS was <28%.[25]

Statistical analysis

Data from continuous variables were expressed as mean (standard deviation) if they were normally distributed or as medians with interquartile ranges if otherwise; while categorical data were expressed as counts (percentages). All statistical tests were two-sided and carried out to a significance level of P < 0.05. Normality of continuous variables was assessed by the Shapiro–Wilk's test. Differences in categorical variables were compared using Chi-square (χ2) analysis. Comparison of means among the groups was by analysis of variance, followed by Duncan new multiple range post hoc test for group comparison. Comparison of variables between participants with or without LVSD was done using Student's t-test. Logistic regression models were used to evaluate the independent correlates of echocardiographic LVH and the presence of LVSD. The statistical program used was R, Version 3.3.1[26]


  Results Top


A total of 161 hypertensive participants comprising 51, 50, and 60 participants in groups 1, 2, and 3, respectively, were studied. Group 1: hypertensive participants with ECG evidence of LVH with strain, Group 2: hypertensive participants with ECG evidence of LVH by voltage criteria only, Group 3: hypertensive participants with normal ECG. [Table 1] shows the basic characteristics of the participants. The mean ages of the participants were 54.0 (19.50), 56.5 (15.00), and 56.0 (17.00) years in Groups 1, 2, and 3, respectively. There was a slight preponderance of female participants in the whole study population, but there was no significant difference in the gender distribution among the three groups. The mean diastolic blood pressure (DBP) and mean arterial blood pressures (MAP) were higher in Group 1 participants compared with those in Group 2, but the difference was not statistically significant. Group 3 participants, however, had significantly lower DBP and MAP compared with the other groups.
Table 1: Basic characteristics of the study population by group

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Echocardiographic measurements and parameters

[Table 2] shows the echocardiographic parameters of the study population by the group. Group 1 participants had significantly higher LV wall dimensions, LV internal dimensions, LV volumes, and LVMI compared with groups 2 and 3. The FS and the EFs were similar across the groups.
Table 2: Echocardiographic parameters of the study population by group

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Echocardiographic derived left ventricular hypertrophy and geometry

A significantly higher proportion of participants in Group 1 (82.3%) compared with Groups 2 (64.0%) and 3 (55%) had echocardiographic derived LVH. Group 1 participants had more hypertrophic geometric patterns: 52.9% with concentric hypertrophy, and 29.4% with eccentric hypertrophy, compared with participants in groups 2 and 3 [Table 2].

A step-wise logistic regression model involving the presence of LVH as the outcome variable and the presence of ECG LV strain pattern, age, BMI, DBP, and gender as independent variables was examined. Only the presence of ECG LV strain pattern and the BMI remained as independent correlates of LVH among the study participants [Table 3].
Table 3: Independent determinants of left ventricular hypertrophy

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Left ventricular systolic dysfunction

LVSD was present in 45.1% of the participants in Group 1 compared with 26% and 21.7% of the participants in Groups 2 and 3, respectively, P = 0.02. [Table 4] shows the basic characteristics of participants with or without LVSD. There was no significant difference in the basic characteristics of those with or without LVSD except for a higher mean BSA in the former.
Table 4: Basic characteristics of participants with or without left ventricular systolic dysfunction

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A step-wise logistic regression model exploring the independent relations of LVSD in the study participants was examined. The independent variables included in the model were the presence of ECG LV strain pattern, age, BSA, DBP, gender, and the pulse rate. The presence of ECG strain pattern and the BSA were the only independent correlates of LVSD in this study [Table 5].
Table 5: Correlates of left ventricular systolic dysfunction

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  Discussion Top


Routine echocardiographic assessment of LV size and function in hypertensive individuals is desirable, but in resource-challenged African countries where this may be impracticable, it is important to identify patients who after ECG evaluation would benefit from further evaluation with echocardiography. The mean age of participants in this study was similar to the age group reported in similar studies in Africa,[16],[27] Our study showed a slight preponderance of females similar to observations from the heart of Soweto study which showed that cardiac complications of hypertension in black Africans occurred more commonly in women.[27] We observed in this study that participants with LVH with strain had higher blood pressure parameters than participants with normal ECG. Poorer blood pressure control has been positively associated with target organ damage in hypertensives.[28],[29]

Relationship of electrocardiographic left ventricular hypertrophy with strain to echocardiographic derived left ventricular hypertrophy

The findings in this study showed that ECG LVH with strain was associated with higher mean LVMI and a higher proportion of participants with echocardiographic derived LVH. Our findings also showed that the presence of ECG LV strain pattern was an independent correlate of echocardiographic derived LVH. These findings were similar to those reported in other studies [8],[16], and support previously suggested explanations offered in the LIFE study, for the poorer prognosis associated with the strain pattern.[8] It has been documented that higher LVMI and echocardiographic-derived LVH are associated with increased cardiovascular risk and poorer prognosis in individuals with hypertension.[30],[31],[32],[33]

Echocardiographic derived LVH was recorded in a higher proportion (82.3%) of our participants who had LVH with strain compared to the 40.6% reported by Ogah et al.[16] in a similar study in Nigeria. A higher mean LVMI (62.4 ± 27.02) and higher prevalence (82.3%) of echocardiographic derived LVH were recorded among participants who had LVH with strain in our study compared to the values of 53.9 ± 29.3 and 40.6%, respectively, reported in the similar study in Nigeria.[16] In this study, LVH with strain was associated with significantly higher aortic root (AO), left atrial (LA), and LV wall dimensions. Our finding is similar to that reported by Salles et al.[28] who demonstrated an independent association of ECG LV strain pattern with increased LV wall thickness and LVMI in the setting of uncontrolled blood pressure. Participants with ECG LVH strain pattern in our study also had higher mean DBP compared with the other participants. Our finding, however, differs from that of Ogah et al.[16] who reported no significant difference in the AO and LV wall dimensions of those with or without LV strain pattern. Our participants had slightly higher mean DBP compared with theirs; it is possible that our participants had more severe hypertension.

Relationship of electrocardiographic left ventricular hypertrophy with strain to left ventricular geometry

Nearly all the participants with ECG LVH with strain in this study compared with the other two groups had abnormal LV geometry, with more than a quarter of them having hypertrophic geometric pattern. This is comparable to the pattern reported in the study by Ogah et al.[16] Concentric hypertrophy was the most common LV geometric pattern associated with ECG LVH with strain in our study. Eccentric hypertrophy also occurred more commonly in ECG LVH with strain than in those without this ECG feature. This finding may further explain the poorer prognosis associated with the strain pattern as concentric hypertrophy has been identified as the LV geometric pattern with the worst prognosis followed by eccentric hypertrophy.[3],[34] Our finding is similar to that of Okin et al.[8] who reported that ECG LV strain pattern was most strongly related to increased risk of concentric hypertrophy and strongly associated with eccentric hypertrophy. Our finding, however, contrasts with the study [16] that reported eccentric hypertrophy as the most prevalent geometric pattern associated with ECG LV strain pattern. In another study conducted in Nigeria [35] which included both old and newly diagnosed hypertensives, concentric hypertrophy was more common than eccentric hypertrophy, and the participants who had concentric hypertrophy had higher blood pressure levels and longer duration of hypertension.[35] They, however, did not include ECG LVH features in the selection of their participants in that study. Although Devereux and Reichek [36] and Roman et al.[37] have also related the ECG strain pattern more strongly with eccentric geometric hypertrophy, those studies were not conducted exclusively in hypertensive individuals.

Relationship of electrocardiographic left ventricular hypertrophy with strain to left ventricular systolic function

The findings in this study showed that the ECG LVH with strain was significantly associated with higher LV internal dimensions and volumes, but insignificantly associated with lower EF and FS. Our findings were comparable with documented report by other workers.[16]

In this study, a significantly higher proportion of participants who had ECG LVH with strain compared with those who had ECG LVH by voltage criteria or normal ECG had echocardiographic evidence of LVSD. The presence of the ECG LV strain pattern was the strongest independent correlate of LVSD in our study. Possible explanations for these findings in our study include the higher LVMI and the higher prevalence of eccentric hypertrophy geometry associated with ECG LVH with strain in the study. Both increased LVMI and eccentric hypertrophy geometry have been reported to be independent risk factors for the development of LVSD.[38] Our findings however differ from that of Okin et al.[8] who reported evidence of impaired LV systolic function in association with the ECG strain pattern only in hypertensive participants who also had evidence of coronary heart disease, in spite of their finding of a strong association between ECG strain pattern and increased LVMI.

Subclinical increase in LV internal dimensions and LVSD as seen in our study participants have been documented by the Framingham heart study group to be independent predictors of cardiovascular risk,[39] and the presence of ECG LV strain pattern has been shown to predict the risk of developing or dying from congestive heart failure in hypertensive patients who were previously asymptomatic for heart failure.[13] Although Devereux and Reichek [36] and Roman et al.[37] also reported the association of ECG LV strain pattern with the presence of increased LV internal dimensions and LVSD, their studies were not in hypertensives. A limiting factor in this study may be related to the reported association of ECG strain pattern with covert coronary artery disease (CAD) in one study.[40] However, the relative rarity of CAD in indigenous black Africans,[41],[42] the exclusion of participants with regional wall motion abnormality and the reported higher prevalence of ECG strain pattern in black participants who had no evidence of CAD [8] should reduce the weight of such limitation.


  Conclusion Top


The findings from this study suggest that the ECG LVH with strain is associated with more severe increase in LVMI, a higher prevalence of echocardiographic derived LVH, an increased tendency toward hypertrophic LV geometry and LVSD in Nigerian hypertensives. Therefore, ECG LVH with strain can be said to identify a group of hypertensive individuals who are at increased cardiovascular risk and should benefit from further evaluation by echocardiography. Where echocardiography may not be readily accessible, this ECG pattern may aid decision-making on appropriate therapeutic intervention.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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