The burden of cardiac diseases is a major problem in the world, with hypertension, ischemic heart disease, and cardiomyopathies as major causes of mortality among people.[
] It is now well established that left ventricular hypertrophy (LVH) determined by 1 echocardiography, is a strong predictor of poor prognosis in cardiovascular disorders independent of traditional risk factors.[ ] 1
This is particularly worse in developing countries in Africa, where there is an increased burden of both communicable diseases and noncommunicable diseases, (for which hypertension and cancers are prevalent).[
2 ] This may result in loss of workforce, financial stress on caregivers and may also have other socioeconomic implications. 3
Hypertension particularly is found to be more prevalent among Africans.[
2 ] Patients with hypertension have many target organ damage, for which heart disease is an example. Others include stroke and chronic kidney disease. Hypertension is one of the most important risk factors for cardiovascular diseases.[ 3 ] Hypertension notably causes problems of impaired relaxation of the heart (diastolic dysfunction), and this has been found to impact negatively on the heart chamber size, particularly the left atrium and left ventricle.[ 4 ] 2
Four different geometric patterns of LV adaptation to chronic hypertension have been identified by studies[
5 6 ] using the combinations of LV mass index (LVMI) and relative wall thickness (RWT). The heart may adapt to hypertension by developing concentric hypertrophy (CH) with increased LVMI and RWT, eccentric hypertrophy[ 7 ] with increased LVMI and normal RWT, concentric remodeling (CR) with normal LVMI and increased RWT, or by retaining normal geometry[ 2 ] with both normal LVMI and RWT. 8
et al.[ ] studying 100 consecutive individuals who were newly diagnosed with hypertension and 50 apparently normal individuals showed that LV mass and index were higher among newly diagnosed hypertensives than normotensive controls. CH was shown to be more prevalent than eccentric hypertrophy. Adebayo 9 et al.[ ] showed from a study done in Ife (Western Nigeria) that concentric geometric patterns were more prevalent among hypertensive individuals. They attributed their findings to environmental factors, ethnic differences, and genetic variability. Wachtell 10 et al.[ ] in the LIFE multicenter study group reported, the prevalence of LVH to be 42%–78% they found the eccentric model to be the highest. Krumholz 11 et al.[ ] found that the prevalence of LVH among a population without hypertension was 28% for women and 24% for men. 12
LVH causes LV diastolic dysfunction, which has been shown to increase left atrial (LV) size. Ogah and Bamgboye[
] studied the correlates and determinants of LV mass in 285 hypertensive individuals and found that LV wall tension, LV wall stress, LV size, diastolic blood pressure (DBP), alcohol consumption, and a family history of hypertension were the independent predictors of LV mass. Adebiyi 13 et al.[ ] studied correlates of LA size among 361 patients on follow-up in the cardiology unit of University College Hospital, Ibadan, and found that the prevalence of eccentric hypertrophy was highest among patients with dilated left atrium compared to those with the normal left atrium. The individuals with dilated LA had higher age, body mass index, LV end-diastolic diameter, LV wall thickness, lower ejection fraction, and fractional shortening when compared to those with the normal left atrium. Body mass index and LV mass were the major predictors of LA size. Adebayo 14 et al.[ ] demonstrated from their work that LV size was highest among those with eccentric hypertrophy (3.67 cm), CH (3.58 cm), normal LV size (3.27 cm), CR (3.21 cm) in descending order. These differences were statistically significant ( 9 P = 0.0004). There have been conflicting data on the pattern of LVH in relation to increased LV size. Cioffi et al.[ ] studied the relationship between LV geometry, LV size and function in 110 concentric and 226 eccentric groups of patients with systemic hypertension. They showed that concentric LV geometry is associated with greater LV size and ejection force than eccentric geometry, suggesting that increased LV stiffness has a greater effect on stimulating LV performance than LV end-systolic stress. The degree of LV enlargement similarly depends on LV mass in patients with concentric and eccentric geometry. This study attempts to describe the various patterns of LA structural changes in relation to the size of the left atrium. 15 MATERIALS AND METHODS
The study was carried out on 200 adult hypertensive patients ≥18 years attending consultant cardiology outpatient clinics irrespective of blood pressure control, whether on antihypertensive medications or not. Patients with overt heart failure, cardiomyopathy, suboptimal echocardiographic images, rheumatic valvular heart disease (regurgitation or stenosis), those with atrial fibrillation, and Pregnant women were excluded from the study.
The patients gave informed consent before participating in this study, and Ethical Clearance was obtained for the study from DELSUTH Ethics and Research Committee.
A transthoracic echocardiogram (Xario diagnostics ultrasound system model SSA-660A, Toshiba Medicals) with ECG gating was performed according to established recommendations.[
] The M-mode, two-dimensional (2D) and spectral Doppler and tissue Doppler echocardiographic images were acquired from standard echocardiographic views (parasternal, apical) with all individuals in the left lateral decubitus position. A cardiac ejection fraction was calculated automatically by the echocardiograph machine in the individuals and controls using the 2D-guided M-mode linear method (teichholz) and calculated thus; 8
EF = LVIDd
3 − LVIDs 3/LVIDd 3 (reduced LVEF <50%).
LV systolic function was determined by the calculation of LV ejection fraction.[
] Aortic root diameters, LV diameter, LV end-diastolic and end-systolic diameters (left ventricular internal diameter in diastole [LVIDd] and left ventricular internal diameter in end-systolic, respectively), interventricular septum and posterior wall diastolic thickness (IVSd and PWd, respectively) were measured in the parasternal long-axis view during M-mode tracing at the peak of the QRS according to the recommendation of the American Society of 8 Echocardiography (ASE). LV mass (LVM) in grams was calculated by the Devereux modified ASE cube formula LVM = 0.80 [1.04 (LVIDd + IVSd + PWd) 3 − LVIDd 3] + 0.6. LVMi was calculated as follows: LVMi = LVM/Body surface area (BSA). RWT was calculated as the ratio (IVSd + PWd)/LVIDd. BSA was computed from body weight and height by the echo machine.[ ] 8
Normal echocardiographic values for LV dimensions are stated below:[
Systolic blood pressure (SBP) and DBP readings were measured with an Accoson mercury sphygmomanometer with the individuals seated and well rested for 15 min. Blood pressure was taken from both arms and the arm with the higher value was used for that participant. The pulse rate of the participants was taken. SBP and DBP readings were determined by the first and fifth Korotkoff phases, respectively. Where the fifth korotkoff was not heard, the fourth korotkoff was used as the value of the diastolic pressure. Patients were considered hypertensive if they had a resting SBP of $ 140 mmHg and/or DBP of 90 mmHg. Furthermore, pulse pressure (systolic minus diastolic) and mean arterial pressure (one-third pulse pressure plus diastolic pressure) were calculated.
Data management and statistical analysis
A semi-structured interviewer-administered questionnaire was used for each participant recruited. Frequency distributions and two-way tables were used to summarize the data. Data obtained were entered into and analysed using IBM Corp. Released 2013. IBM SPSS Statistics for Windows, Version 22.0. (Armonk, NY: IBM Corp). Continuous variables (age, LA and LV dimensions, blood pressure, etc.) were expressed as mean ± standard deviation (SD); categorical data (sex, marital status, ECG- LV enlargement), as percentages. Differences in continuous and categorical variables between cases and controls were assessed by unpaired samples Student's
t-tests and χ 2 analyses, respectively. Differences in LA size between groups of patients with different LV dysfunction (isolated systolic, isolated diastolic, systolic, and diastolic) were assessed by one-way ANOVA, followed by the Bonferroni post hoc test. Multivariate correlations between LA indices and LV cardiac indices among the groups of cases and controls were assessed with Pearson's correlation coefficients. A two-tailed P < 0.05 was considered statistically significant. RESULTS
As seen in
Tables 1- 3 as well as Figure 1 during the study period, a total of two hundred hypertensive patients were recruited. The mean age of the study population was 58.42 ± 13.29 years, while the median age was 59 years. The number of males and females in the study was almost equal. Figure 1:
LA enlargement and LV geometry of cases. LA: Left atrial, LV: Left ventricular.
Demographic and clinical parameters of study population
Two-dimensional and Doppler echocardiographic characteristics of different geometric patterns in hypertensive individuals
Left ventricular parameters between men and women
Ninety-two percent were married, 4.5% were single, while 3.5% were widows/widowers.
Majority of the study population were traders (77%), while the controls were predominantly farmers (33%). Other occupations represented included Lawyers, Students, Civil servants, Clergy, Fashion designers, and Housewives.
The most common ethnic group was Urhobos (42.5% of cases and 60% of controls). This was closely followed by the Isokos, Igbo, Itsekiri, and others (Esan, Ijaw, Yoruba, and Bini) in descending order. Twenty-five percent of the study population had a family history of hypertension. Twenty-one percent of the study population were alcohol users.
Majority of the patients (55%) were on two antihypertensive medications. Twenty-six percent were on monotherapy, 18% were on three medications, and only 1% was on either four or more antihypertensives. Majority of the patients were on diuretics (59%), while other hypertensive drugs used were angiotensin-converting enzyme inhibitors (48.5%), calcium channel blockers (44%), angiotensin receptor blockers (22.5%), beta blockers (17%).
The prevalence of LV enlargement was found to be 16% and 59% using LA linear diameter and LA maximum volume, respectively.
While 28.5% of the population had normal LV geometric patterns, 71.5% had abnormal LV geometric patterns. Among them, 31.5% had CR, 27.5% had CH, and only 12.5% had eccentric hypertrophy.
Thirty-one (54.4%) of the patients with normal LV geometry and 35 (55.6%) of those with CR had LA volume enlargement on
echocardiography. Forty (72.7%) of the patients with CH had LA volume enlargement and 12 (48%) of the patients with eccentric hypertrophy had LA volume enlargement on echocardiography. DISCUSSION
Hypertension is known to impact negatively on the heart, causing LV diastolic dysfunction, which precedes a sequel of anatomical and functional changes in the left atrium.
The prevalence of LV enlargement in the hypertensive group was found to be 16% and 59% using LA linear diameter and LA maximum volume, respectively. This prevalence is in keeping with a systematic review done by Cuspidi
et al. that found the prevalence of echocardiographic LA enlargement to vary between 16% and 83%, the studies applied both LA linear diameter and LA maximum volume for LA size measurement.[ ] Adebiyi 16 et al. in a hospital-based study done in Ibadan, Nigeria, found the prevalence of LA enlargement among newly diagnosed hypertensive individualsto be 15.8% using LA linear diameter.[ ] 14
E/E' significantly correlated positively with all phasic LA volumes compared to E/A ratio, which only correlated with LA maximum volume, and no correlation was seen with LA linear diameter. The mitral E/E' which is derived from tissue Doppler may be better than the mitral E/A ratio because the latter is more subject to loading conditions of the heart than the former. Also of note is that LV mass, and pulmonary A wave duration were shown to be independent predictors of increased LV linear diameter amongst hypertensives with isolated LV diastolic dysfunction. LV mass independently predicted all LA phasic volumes (maximum, pre-A wave, and minimum). This finding is in agreement with that of Aje
et al.[ ] who showed that LV mass was an independent predictor of LV size. Bamikole[ 17 ] demonstrated a positively significant correlation between the LA volume index and E/E' ratio. It can be deduced that progressive increases in LV mass can herald changes in LV size which may be associated with cardiovascular events for this group of patients. This may warrant the need for echocardiographic assessments and monitoring for patients with an early increase in LV mass. 18
This study found LV size to be highest among those with concentric patterns of hypertrophy compared to the eccentric geometric pattern. While this agrees with findings by Cioffi
et al.,[ ] the reverse was discovered by Adebayo 15 et al.[ ] This finding suggests a pressure overload relationship as opposed to volume overload as a possible mechanism of dilatation of the left atrium. CH is associated with reduced compliance due to increased stiffness of the left ventricle leading to diastolic dysfunction. This, in turn, decreases the rate and volume of rapid filling of the left ventricle. The findings may suggest that LV pressure overload is more likely to impact on LA size than volume overload. This may be as a result of increased afterload in the left ventricle, leading to impairment of diastolic filling. However, more studies are needed to corroborate this assumption. 10 CONCLUSION
Although CR of the LV is the most common type of geometric change among hypertensive patients, patients with dilated left atrium are likely to have the concentric type of LVH than the eccentric type.
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Conflicts of interest
There are no conflicts of interest.
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