Study of hypertension mediated organ damage in a group of hypertensive patients in Cameroon: a cross-sectional study

¹Faculty of Medicine and Biomedical Sciences, University of Yaoundé 1, Yaoundé, Cameroon, ²School of Health and Medical Science, Catholic University of Cameroon, Bamenda, Cameroon

^&Corresponding author
Chris Nadège Nganou-Gnindjio, Faculty of Medicine and Biomedical Sciences, University of Yaoundé 1, Yaoundé, Cameroon

Introduction    

Hypertension-mediated organ damage (HMOD) is the structural and/or functional alteration of the arterial vasculature of the organs it supplies due to elevated blood pressure [1]. End organs include the brain, the retina, the heart, the kidneys, and central and peripheral arteries [1]. A community-based Framingham Study with 7898 participants was done to assess hypertension-mediated organ damage, and it was found that elevated carotid-femoral pulse wave velocity was the most prevalent, while low ankle-brachial index was the least prevalent. Left ventricular hypertrophy, reduced kidney function, microalbuminuria, increased carotid intima-media thickness, and abnormal brain imaging findings had an intermediate prevalence [2]. In 2017, it was shown that the prevalence of Hypertension-mediated organ damage in non-adherent patients to therapeutic guidelines was 40.3% [3]. Hypertension-mediated organ damage was prevalent at 23.2% among patients attending outpatient consultations, with kidney disease being the most frequent [4]. In 2018, in Cameroon, it was found that 84.6% of patients newly diagnosed with hypertension presented with at least one target organ damage at diagnosis [5].

Numerous studies have demonstrated the relationship between high blood pressure and different types of Hypertension-mediated organ damage [6,7]. Early markers of the syndrome are often present before the diagnosis of hypertension [8]. Progression is strongly associated with functional and structural target organ damage and leads to premature morbidity and death [8]. The relationship between cardiovascular events and high blood pressure is well known, and increased blood pressure is closely linked with increased cardiovascular events [2,9,10]. Initial evaluation of organ damage in all hypertensive patients will serve as an essential baseline for the management and follow-up [11]. Detection of Hypertension-mediated organ damage is not likely to change the management of those patients already identified as high risk but provides necessary therapeutic guidance based on the specific impact of the damaged organs [1]. High blood pressure is a significant contributor to morbidity and mortality worldwide; despite this burden, blood pressure control remains unsatisfactory [12]. In Africa, we are sorely lacking in data on hypertension mediated organ damage [13]. Consequently, the determinants of the latter, as well as the severity of target organ damage, are not well-defined in our context, and Cameroon is no exception to this reality. Identifying target organ damage could help estimate the burden of high cardiovascular risk in the hypertensive population, and earlier screening and detection may positively impact the management and reduce cardiovascular events. Therefore, it is important to show the burden of Hypertension-mediated organ damage among diagnosed hypertensive patients in Cameroon. This study aimed to determine the prevalence and factors associated with hypertension-mediated organ damage among patients at Yaoundé General Hospital and Yaoundé Central Hospital in Cameroon.

Methods     

Study design and setting: we conducted a cross-sectional study with prospective data collection in the cardiology department of Yaoundé Central Hospital (YCH) and the internal medicine department of Yaoundé General Hospital (YGH) over eight months from October 2023 to May 2024. These departments have high-quality technical resources for treating sub-Saharan African cardiovascular diseases, including high blood pressure and its complications.

Study population: the target population was Cameroonian hypertensive patients. The source population consisted of patients with a known diagnosis of hypertension with or without treatment and comorbidities attending consultations in those health facilities. All patients older than 18 years with a known diagnosis of hypertension who were willing to participate in the study were included. We excluded pregnant patients and patients with a known diagnosis of glaucoma (Figure 1). A consecutive sampling method was used. This includes the consecutive selection of every participant with the inclusion criteria over the specified time interval. The sample size was estimated to be 201 participants using the Lorentz formula [14] and the prevalence of Nagano-Gnindjio et al. (84.6%) [5].

Data collection: after obtaining ethical clearance and authorisation from the Directors of the Yaoundé General and Central hospitals, patients with hypertension attending consultation at the internal medicine department (more specifically, the cardiology, nephrology/dialysis and neurology units) of these hospitals were invited to participate in our study. Once we met the patients, we thoroughly informed them of the study, its aims, procedure, possible inconveniences, and confidentiality and gave them an information form. Those who met the inclusion criteria and were willing to participate were required to sign a consent form, which helped us fill out a data collection tool comprising demographic and clinical data. Participants will undergo a series of assignments. First, we will identify them with a code, fill the demographic data based on the answer of the patients or the caregiver, the clinical data will be filled based on patient's answers, most recent patient's medical records (not more than six months), physical examination including brachial and ankle blood pressure using an automatic sphygmomanometer (bp-103H), waist and hip circumference, fundoscopy and urinary dipstick. The main organs assessed were the heart by using electrocardiogram and/or cardiac ultrasound (with a Philips IE33 ultrasound machine), kidneys (serum creatinine and urine dipstick for proteinuria), brain (medical report of transient ischaemic attack or stroke), arteries of the lower limbs (ankle-brachial index) and the retina (fundoscopy).

Definition of terms

Heart damage: was defined as evidence of left ventricular hypertrophy, dilated cardiopathy, any form of coronary artery disease (myocardial injury, ischaemia, infarction old or recent) atrial fibrillation, or any relevant cardiopathy secondary to hypertension seen on ECG (electrocardiogram) and/or echocardiography.

Brain damage: was defined as a medical history of transient ischaemic attack, ischaemic or haemorrhagic stroke or subarachnoid haemorrhage confirmed by the and brain CT scan without contrast.

Kidney damage: was defined as evidence of at least 1+ proteinuria on urine dipstick, serum creatinine greater than 1.3mg/dl for men and 1.1 mg/dl for female, and/or confirmed CKD (chronic kidney disease) secondary to hypertension by the attending physician.

Retina damage: was defined as evidence of retinopathy as from Kirkendall classification stage I: diffuse arteriolar narrowing, stage II: cotton wool, exudate, and haemorrhage, with or without stage 1, stage 3: evidence of papilledema with or without stage 2 [1].

Vascular damage: was defined as ankle brachial index less than 0.9 [1].

Hypertension: was defined as reported systolic blood pressure value ≥ 140mmHg and/or diastolic blood pressure value ≥ 90mmHg [1].

Chronic hypertension: was defined as hypertension diagnosed at least 6 months ago.

Secondary hypertension: was defined as Hypertension with a secondary cause; when no cause was found, it was considered as primary [1].

Statistical analysis: data was analysed using SPSS version 23.0. Qualitative variables were described as frequencies and percentages. Quantitative data were described by mean, and their dispersion was expressed with standard deviation. We used the CHESKIN method to determine the OR and p statistics of variables for which a subject can have several choices. In our specific case, a person with a target organ lesion may at the same time have a brain, heart, retina or kidney lesion. As a result, we need to compare the different frequencies of specific target organ damage with subjects who have no target organ damage (reference value). Data were considered statistically significant for a threshold of p ≤ 0.05.

Ethical considerations: the Institutional Ethical Review Board of the Catholic University of Cameroon (CATUC) approved the study, and the ethics clearance number 004/CATUC-IRB/WFM/LKN/24 was obtained. Before the survey, we received authorisation number 185/24/AP/MINSANTE/SG/DHCY/CM/SM from the Yaoundé Central Hospital and authorisation number 027-24/HGY/DG/DPM/APM-TR from the Yaoundé General Hospital. We also received free, informed, and signed consent from the various participants. The data used in this study were anonymised before use.

Results     

Sociodemographic characteristics of the sample: of the 214 participants recruited, the mean age was 57.64 ± 12.94 years, with extreme of 25 and 90 years. Most patients were 65 and older, with 69 (32.2%) cases (Table 1). The proportion of female was 53.3%.

Clinical characteristics of the sample: we have 49 (22.9%) newly diagnosed patients shown in Table 1. Most of the patients had essential hypertension, with 192 (89.7%) cases. The most common cardiovascular risk factors were overweight/obesity with 134 (62.6%) patients, sedentary lifestyle with 130 (60.7%) patients and dyslipidaemia with 51 (23.8%) patients. The most commonly prescribed drugs were calcium channel blockers, with 116 (74.4%) cases; ACEi (Angiotensin-converting enzyme inhibitors)/ARBs (Angiotensin receptor blockers), with 94 (60.3%) cases; and thiazide diuretics, with 68 (43.6%) cases. The mean systolic blood pressure was 165.43 ± 40.13 mmHg, and diastolic pressure was 101.17 ± 23.58 mmHg. Most of the participants had grade 3 hypertension, with 93 (43.5%) being systolic and 89 (41.6%) being diastolic. The frequency of grade 3 hypertension was higher among newly diagnosed patients, with proportions being 55.1%, but it was not statistically significant (p=0.093).

Factors associated with target organ damage: the number of participants with at least one target organ damage was 187 (87.4%) as shown in Table 2. Among these participants, 134 (62.6%) had two target organs damaged, and 62 (29.0%) had three or more. The most commonly involved organs were the kidneys, with 109 (58.3%) cases; the retina, with 108 (57.7%) cases; and the heart, with 92 (49.2%) cases. Concerning the stratification of target organ damage, increased creatinaemia (47.2%), diffuse arteriolar narrowing (40.2%), left ventricular hypertrophy (33.6%) and ischaemic stroke (15.9%) were the most representative for the retina, kidneys, heart and brain respectively. Up to 75.5% of newly diagnosed participants were having at least one target organ damage. Patients whose hypertension had been present for 6 months or more were 3.24 times more likely to have a target organ lesion (95% CI 1.40-7.51; p = 0.006), specifically renal damage (OR = 4.65; p = 0.001), then cardiac (OR = 3.07; p = 0.015), then cerebral (OR=2.93; p = 0.022) and finally retinal (OR = 2.80; p = 0.022) (Table 3). As shown in Table 4, patients with grade 3 hypertension had a 2. 70 times greater risk of target organ damage (95% CI: 1.09-6.70; p = 0.031), specifically retinal damage (OR=4.66; p = 0.001) and cerebral damage (OR: 3.80; p = 0.006).

Discussion     

This study aimed to show the burden of hypertension-mediated organ damage among patients at Yaoundé General Hospital and Yaoundé Central Hospital in Cameroon. Our study showed that 87.4% of the population had at least one target organ affected. The main target organs were the kidney (58.3%) and the retina (57.7%). Patients whose hypertension had been present for 6 months or more were 3.24 times more likely to have a target organ lesion (95% CI 1.40-7.51; p = 0.006) and those with grade 3 hypertension had a 2. 70 times greater risk of target organ damage (95% CI: 1.09-6.70; p = 0.031). Our study's population mean age was 57.64 ± 12.94 years, with extremes of 25 and 90 years. These results are similar to those of Nagano-Gnindjio et al. and Lembo et al. who found mean ages of 57±12 years and 53.8 ± 11.4 years, respectively [5,10]. Most (32.2%) patients were 65 years old (Table 1). The advanced mean age of our population is because, in most cases, arterial hypertension was essential hypertension. The female sex was predominant, with a sex ratio (M/F) of 0.88. Nganou-Gnindjio et al. also found a predominant proportion of women [5]. The advanced age of the population may explain this. Due to the loss of estrogen-induced cardioprotection during menopause, older women are more likely to develop essential hypertension, with a higher risk than men over 60 years.

The most identified cardiovascular risk factors were overweight/obesity (62.6%), sedentary lifestyle (60.7%) and dyslipidaemia (23.8%). Similar results were seen by Nganou-Gnindjio et al. [5]. This can be explained by the fact that both studies were done in Cameroon, and our data collection sites were similar. A sedentary lifestyle and overweight/obesity are closely linked; a sedentary lifestyle increases the development of overweight and obesity [15], and those two are common modifiable cardiovascular risk factors encountered in many studies [16]. Our results opposed Sun Oh et al. where diabetes represented the most common cardiovascular risk factor [17]. This can be explained by the fact that a sedentary lifestyle was not evaluated, and the candidates were veterans. Management of hypertension was based on oral antihypertensive treatment (72.9%) and diet modification (34.6%). Calcium channel blockers (74.4%), ACEi/ARBs (60.3%) and thiazide diuretics (43.6%) were the most commonly prescribed drugs. These drugs are recommended for first-line use by the European Society of Hypertension in the management of hypertension in black subjects [18]. The mean systolic blood pressure was 165.43±40.13 mmHg and diastolic of 101.17±23.58 mmHg. Similar to the result obtained by Lembo et al. where the mean systolic blood pressure was 142.7±18.4mmHg, and the mean diastolic blood pressure was 88.8 ± 11.1mmHg [10]. This was contrasted by Vasan et al. with mean systolic blood pressure of 122±17 mmHg and mean diastolic blood pressure of 74±10 mmHg [2]. Concerning the systolic blood pressure variation, 68.2% of participants had a systolic blood pressure ≥ 140 mmHg, and up to 43.4% had grade 3 systolic hypertension. For the diastolic blood pressure variation, 61.2% had diastolic blood pressure ≥ 90mmHg and 41.6 with grade 3 diastolic hypertension. For both systolic and diastolic blood pressure, grade 3 hypertension was mainly present in newly diagnosed hypertensive patients, but was not statistically significant (p=0.093). All these results can be explained by the fact that our study was hospital-based, involving the emergency unit where hypertensive presentations are generally grade 3, newly diagnosed have at least systolic blood pressure ≥ 140mmHg and others present with hypertensive crisis.

We found that 87.4% of participants had at least one target organ damage. Among these participants, 62.6% had two target organs damaged, and 29.0% had three or more. This result is comparable to Nganou-Gnindjio et al. (84.6%), who evaluated the target organ damage in newly diagnosed hypertensive patients [5]. This may be explained by the late diagnosis and data collection settings. Vasan et al. and Lembo et al. had a slightly lower prevalence. In their studies, the prevalence of hypertension-mediated organ damage was 75% and 64.4% respectively [2,10]. This can be explained by a larger sample size and the methodology used where only left ventricular hypertrophy and an eGFI <60 mL/min/1.73 m² were used to characterise heart and kidney damage, respectively [2,10]. The prevalence of hypertension-mediated organ damage varies widely across various studies according to the methodology, the race and the choice of the screening tests. Concerning the stratification of hypertension-mediated organ damage, kidneys and the retina were the most affected organs, with a prevalence of 58.3% and 57.7%, respectively. The search for hypertensive retinopathy is not often carried out systematically in our context. In view of its high prevalence, it should be included in the organ damage assessment of every hypertensive patient.

Heart and brain damage were intermediate at 49.2% and 44.9%, respectively, and peripheral artery disease had the least prevalence with 2.1%. Wang et al. and Sun Oh et al. also found the kidneys as the most affected organ damage. This was followed by the heart (left ventricular hypertrophy) [9,17]. This can be explained by the fact that these manifestations are usually symptomless, and discovery is based on results from investigations that generally reveal a greater prevalence than expected. Results from Vasan et al. were contrasted to this, where increased carotid-femoral pulse wave velocity was the most frequent hypertension-mediated organ damage [2]. This can be justified by the fact that carotid-femoral pulse wave velocity is not frequently performed in our context, and it is a known indicator of the development of hypertension and its evolution [2,19]. Other studies have shown that heart damage with left ventricular hypertrophy was the most common manifestation of target organ damage. This can be explained by the fact that most of those studies were carried out in the cardiology units, some using just microalbuminuria and/or chronic kidney disease and/or eGFR (estimated glomerular filtration rate) <60 mL/min/1.73 m² as markers of kidney damage [3,20-22]. The most typical manifestation of each target organ damage was increased creatinaemia (47.2%), diffuse arteriolar narrowing (40.2%), left ventricular hypertrophy (33.6%) and ischaemic stroke (15.9%) were the most representative for the retina, kidneys, heart and brain respectively. This can be explained by the fact that most of those presentations are asymptomatic, allowing the continuous effect of high blood pressure on different organs before diagnosis.

Also, it was shown in our study that target organ damage was linked with the duration of hypertension, patients whose hypertension had been present for 6 months or more were 3.24 times more likely to have a target organ lesion, renal damage being the most closely related to the duration of hypertension (OR = 4.65; p = 0.001) followed by cardiac damage (OR = 3.07; p = 0.015). This can be explained by the fact that hypertension, in its evolution, leads to glomerular sclerosis with results in decreased eGFR, proteinuria and chronic kidney disease. The same results were seen by Sun Oh et al. despite our smaller sample size because we used the same methodology to define kidney damage [17]. Cardiac damage is due to the fact that hypertension leads to remodelling of the cardiac cavities, which, if left untreated, will worsen over time. Patients with grade 3 hypertension had a 2. 70 times greater risk of target organ damage, specifically retinal damage (OR=4.66; p = 0.001) and cerebral damage (OR: 3.80; p = 0.006). The same results have been seen by Vasan et al. and Wang et al. relating hypertension-mediated organ damage to the severity of hypertension [2,9]. There is a proportional relationship between the grade of hypertension and the degree of target organ damage [23]. In view of all this, patients with severe and long-lasting hypertension should benefit from a more thorough investigation of target organ damage.

The limitations of our study are the relatively small sample size and its design, which does not allow us to completely eliminate the confounding factors of target organ lesions, for example, since around 20% of the population is diabetic, we were unable to formally differentiate between diabetes-related and hypertension-related target organ damage. Nevertheless, this study gives us an idea of the state of HMOD in Cameroon and the factors associated with target organ damage.

Conclusion     

The prevalence of hypertension-mediated organ damage is high in Cameroonian urban setting and is linked with cardiovascular risk factors, duration, and grade of hypertension. The kidneys, retina, and heart are the target organs most involved, with increased serum creatinine, diffuse arteriolar, and left ventricular hypertrophy as the most typical manifestations. Much remains to be done to reduce target organ damage from hypertension, and patients with severe and long-lasting hypertension should benefit from a more thorough investigation of target organ damage.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

Concept and design of the study: Chris Nadège Nganou-Gnindjio, Maimouna Mahamat. Acquisition of data: Chris Nadège Nganou-Gnindjio,Jordan Ridley Donfack Djiloung, Maimouna Mahamat, Jules Thierry Elong. Analysis and interpretation of data: Chris Nadège Nganou-Gnindjio, Jordan Ridley Donfack Djiloung, Maimouna Mahamat, Jules Thierry Elong. Drafting the article: Loïc Alban Mbosso Tasong, Chris Nadège Nganou-Gnindjio. Revising paper critically for important intellectual content: Chris Nadège Nganou-Gnindjio, Maimouna Mahamat, Loïc Alban Mbosso Tasong. All the authors have read and agreed to the final manuscript.

Tables and figure     

Table 1: sociodemographic characteristics and general characteristics of hypertension

Table 2: stratification of organ damage

Table 3: the relationship between duration of diagnosis of hypertension and target organ damage

Table 4: the relationship between grade 3 hypertension and target organ damage

Figure 1: participant flow chart

References