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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 13  |  Issue : 1  |  Page : 18-22

Pattern of left ventricular geometry in Nigerians with prehypertension


1 Department of Medicine, Bayero University/Aminu Kano Teaching Hospital, Kano, Nigeria
2 Department of Medicine, Jos University Teaching Hospital, Jos, Nigeria

Date of Web Publication13-Jan-2016

Correspondence Address:
Saidu Hadiza
Department of Medicine, Bayero University/Aminu Kano Teaching Hospital, Kano State
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0189-7969.173849

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  Abstract 

Background: The previous studies in Western countries have suggested that subjects with prehypertension have a higher risk of developing cardiovascular disease and mortality, increased left ventricular mass (LVM), and abnormal LV geometry, than those with normal blood pressure (BP). The aim of this study was to determine the pattern of LV geometry in Nigerian prehypertensives and compared with those of hypertensives and normotensives.
Methods: This was a cross-sectional comparative study conducted at Aminu Kano Teaching Hospital, Kano, Nigeria. Clinical evaluation and full echocardiographic examination were performed among selected patients with normal BP (group 1), prehypertension (group 2), and hypertension (group 3).
Results: A total of 300 subjects were studied, 100 in each group. The mean age of subjects in group 1 was 27.86 ± 8.60 years, and 60% were female, while that of group 2 was 34.04 ± 6.25 years, and 53% were female, and that for group 3 was 52.62 ± 11.8 years, and 56% were female. About 86% of group 1 had normal geometry (NG) while 12% had concentric LV remodeling concentric remodeling (CR) and 2% had eccentric hypertrophy (EH). Among subjects in group 2, NG was found in 72%, CR in 14%, EH in 12% and concentric hypertrophy (CH), in 2%. In group 3, NG was found in only 21% while 13% of them had CR, 28% CH, and 38% had EH. There was a progressive increase in LVM index from normal BP (30.13 ± 8.53 g/Ht2.7) to prehypertension (33.26 ± 8.95 g/Ht2.7) and to hypertension (48.41 ± 12.4 g/Ht2.7) (P = 0.001).
Conclusion: This study has shown a higher prevalence of abnormal LV geometric patterns and higher LVM among subjects with prehypertension compared with normotensives. Such findings could carry prognostic implication and require further population survey involving a larger group.

Keywords: Geometry, left ventricular hypertrophy, nigerians, prehypertension


How to cite this article:
Hadiza S, Musa KK, Basil O. Pattern of left ventricular geometry in Nigerians with prehypertension. Nig J Cardiol 2016;13:18-22

How to cite this URL:
Hadiza S, Musa KK, Basil O. Pattern of left ventricular geometry in Nigerians with prehypertension. Nig J Cardiol [serial online] 2016 [cited 2019 Aug 21];13:18-22. Available from: http://www.nigjcardiol.org/text.asp?2016/13/1/18/173849


  Introduction Top


Prehypertensives have an increased the risk of developing hypertension and cardiovascular disease compared with those with normal blood pressure (BP).[1],[2] They have also been shown increased left ventricular mass (LVM) than normotensives.[3],[4] The early compromise in the LV structure may therefore mark the beginning of a progressive remodeling of the left ventricle that may go unnoticed for years before the development of hypertension.[4]

Increased LVM is a complication of hypertension and has been shown to be an important predictor of cardiovascular morbidity and mortality.[5],[6],[7] The prognostic importance of the different geometric patterns in hypertensives has also been established. Alterations in LV geometry is associated with increased risk for cardiovascular events, with concentric left ventricular hypertrophy (LVH) carrying the greatest risk.[4],[5],[6],[7]

According to the Framingham study, a 40% rise in the risk of major cardiovascular events can be expected for each 39 g or standard deviation (SD) increases of LVM.[8] LVM and LVM index (LVMI) more than two SDs from normal are defined as echo LVH. Although there is a relatively wide range of published cut-off values, findings from the Framingham Heart Study suggested that normalization of height might be more accurate.[9],[10],[11] Adebiyi et al. however documented LVMI indexed to allometric height as more sensitive in Nigerians.[12]

Data from the sub-Saharan Africa that explores the relationship between prehypertension and LV geometry are scarce. It was therefore decided to determine the LV geometric patterns among prehypertensives in Kano, Nigeria and how they compared with those of hypertensives and normotensives.


  Methods Top


The study was cross-sectional and comparative carried out in Aminu Kano Teaching Hospital, a tertiary healthcare institution in Kano State, North-Western Nigeria. The study protocol was approved by the Research Ethics Committee of the hospital, before the commencement of the study. The study conformed to the Declaration of Helsinki on investigations involving human subjects.[13] The study was explained to the patients in English or in the local language (Hausa) and written consent obtained before enrollment into the study.

Patient selection

The study population comprised of patients at least 18 years of age, attending the Cardiology and General Outpatient (GOP) clinics of the Hospital. There were three patient groups.

  • Group 1: Subjects with normal BP who presented to GOP with minor ailments;
  • Group 2: Prehypertensives who also presented to the GOP with minor ailments; and
  • Group 3: Hypertensive subjects on treatment and attending the Cardiology Clinic.


A total of 300 patients were studied, hundred in each group. Subjects with prehypertension and normal BP that fulfill the inclusion criteria were consecutively selected, whereas the hypertensive patients were selected using simple random sampling.

Exclusion criteria include subjects <18 years of age, pregnant women and those on drugs known to increase BP such as steroids and contraceptive pills. Furthermore, excluded among the prehypertensive and normotensive groups, were subjects with a previous history of hypertension or known to have established diabetes mellitus, chronic renal failure, valvular heart disease, and ischemic heart disease.

Data generation

BP was measured using mercury sphygmomanometer according to the recommendations of American Society of Hypertension.[14] BP levels were defined using the seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of high BP (JNC VII) criteria.[15] Normal BP was defined as systolic BP (SBP) <120 mmHg and/<diastolic blood pressure (DBP) 80 mmHg, whereas SBP of 120–139 mmHg and/DBP of 80–89 mmHg as prehypertension and SBP ≥ 140 mmHg and/DBP ≥90 mmHg as hypertension.[15]

Transthoracic echocardiography was performed using Aloka SSD 4000 machine with 3.5 MHz transducer. The procedure was performed according to the recommendations of the American Society of Echocardiography.[16],[17]

LVM was calculated using the formula that has been shown to yield values closely related to necropsy LV weight (Devereux - modified ASE cube formula).[18] LVM was indexed to the allometric power of height.[19]

LVH was considered present if LVMI ≥46 g 2.7. Relative wall thickness (RWT) was calculated as 2 × PWTd/LVIDd; where PWTd is posterior wall thickness at end-diastole, and LVIDd is LV end-diastolic dimension. Normal RWT was defined as values <0.45 and increased RWT as ≥0.45.[20]

LV geometric patterns were defined as follows: Normal geometry (NG) (normal LV RWT and LVMI); concentric remodeling (CR) (increased LV RWT with normal LVMI); and eccentric LVH (normal LV RWT with increased LVMI). Body mass index (BMI) was calculated as the ratio of the weight (in kilograms) to the square of the height in meters (m 2).

All subjects fasted overnight for 10–12 h after which venous samples were obtained for fasting plasma glucose levels.

Statistical analysis

Statistical analysis was performed with SPSS software version 19.0. Data are reported as mean ± SD for continuous variables and as the frequency for categorical variables. An one-way analysis of variance was used to compare means across the three groups (normal BP, prehypertension, and hypertension). Logistic regression models were used to analyze the associations between LVMI with a number of variables. Pearson's correlation coefficient (r) was employed to examine linear associations. A P ≤ 0.05 was regarded as significant.


  Results Top


A total of 300 patients were studied, 100 in each group. The mean age of the subjects in group 1 was 27.86 ± 8.6 years, 34.04 ± 6.25 years for group 2 and 52.62 ± 11.8 years for group 3. The subjects in group 1 were significantly younger than those in group 2, and those in group 3 were significantly older than those in group 2 (P ≤ 0.001 for each comparison). There were however no significant statistical differences in gender distribution between the three groups (P = 0.3) for each comparison. The other baseline characteristics are shown in [Table 1].
Table 1: Comparison of the baseline characteristics of the study population

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[Table 2] showed that the left atrial size, septal and posterior wall thickness, end diastolic diameter, ejection fraction, fractional shortening, and LVMI were significantly different among the different groups. It also showed the pattern of LV geometry among the three groups. NG was found in 86% of subjects in group 1, 72% of group 2 and only 21% of subjects in group 3.
Table 2: Echocardiographic characteristics of the study population

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The left atrial size and end diastolic diameter were largest among subjects with eccentric hypertrophy while subjects with concentric hypertrophy had higher septal and posterior wall thickness and LV mass index than the other groups. The other echocardiographic parameters are as shown in [Table 3].
Table 3: Echocardiographic characteristics of the different geometric patterns

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Univariate logistic regression analysis showed mean age, SBP, DBP, pulse pressure (PP), fasting blood glucose (FBG), and BMI as a predictors of LVMI among prehypertensives while multivariate logistic regression showed only mean BMI as predictor of LMVI amongst them as shown in [Table 4] and [Table 5], respectively.
Table 4: Univariate analysis showing predictors of LVMI among prehypertensives

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Table 5: Multivariate analysis showing predictors of LVMI among prehypertensives

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Pearson's correlation coefficient also showed a significant association between BMI and LVMI (r = 0.56, P ≤ 0.0001) as shown in [Figure 1].
Figure 1: Effect of variation of body mass index (in kg/m2) on left ventricular mass index, r = 0.56, P < 0.0001. BMI – Body mass index; LVMI – left ventricular mass index

Click here to view



  Discussion Top


The present study has shown that prehypertension was associated with higher LV wall thickness, LVM, RWT, and the higher prevalence of LVH and abnormal LV geometric patterns than normotensives. There was a clear gradient in the prevalence of LVH across the BP categories from normotensives through prehypertensives to hypertension. This finding is consistent with previous reports.[3],[4]

LVH was detected in only 2% of subjects with normal BP but in up to 14% of prehypertensives. This finding is similar to what was reported by Jugal et al. in India, where LVH was reported in up to 17% of prehypertensives.[21] Stabouli et al. in Greece similarly reported the significantly the higher prevalence of LVH among prehypertensive and hypertensive children than normotensives.[22] The highest prevalence of LVH observed among hypertensives in the present study (66%) is consistent with earlier reports.[23],[24],[25],[26],[27]

The various LV geometric patterns are determined to a large extent by whether pressure or volume overload is predominating.[6],[18] CR and concentric hypertrophy (CH) may predominate in early and intermediate hypertensives due to the predominating volume overload, whereas eccentric hypertrophy (EH) progressively takes over with increased LVM due to increase in volume overload.[18] The most prevalent LV geometric pattern among prehypertensives in this study was NG (72%), followed by CR (11%), EH (13%) and then CH (4%). In the Indian sub-continent however, the however higher prevalence of CH (13.79%) was reported among prehypertensives followed by CR (3.44%) and then EH (3.22%). Among the normotensives, CR was the commonest abnormal LV geometry (12%), followed by EH (2%) with 86% having NG. The hypertensive group is having the highest prevalence of abnormal geometry (79%) had EH being the most prevalent (38%) followed by CH (28%), CR (13%), and then NG (21%). This finding is similar to what was previously reported by Karaye and Habib.[23] Other studies however reported different patterns.[24],[25],[26],[27]

Progressive alteration in the geometric pattern of the left ventricle also influences the LV systolic function parameters.[6] As the severity of abnormal geometry progresses, most of the derived systolic indices reduces. Those with EH had the lowest echocardiography derived systolic function. This may suggest the beginning of progressive deterioration of global systolic function in EH. LVH is associated with multiple factors such as BP, increased age, and diabetes resulting in increased stiffness of the left ventricle.[28] Although we reported higher SBP, DBP, MAP, PP, mean age, mean BMI, and mean FBG among prehypertensives than normotensives,[4],[9] multivariable analysis found mean BMI as the only predictor of LVMI among prehypertensives. Similar findings was documented by Stabouli et al.[22] Stephen et al. in the UK however found male sex and heart rate at maximal exercise in addition to BMI as predictors of LVMI.[29] The finding that increased BMI is associated with increased LVMI is also consistent with other studies.[24],[25],[26],[29]


  Conclusion Top


Our study has shown that prehypertensives had the higher LVM, the prevalence of LVH and abnormal LV geometry than normotensives but the lower prevalence when compared with hypertensives. CR was the most common abnormal LV geometry found among prehypertensives, followed by EH. These findings show already existing adverse cardiac remodeling in prehypertensives, and therefore, suggest the need for longitudinal studies involving a larger population group in order to determine the prognostic significance of these findings. The findings could support a recommendation on how best to treat the prehypertensives.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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    Figures

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    Tables

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



 

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