1. Introduction
Human immunodeficiency virus (HIV) is a global health challenge. An estimated global population of 40.8 million was documented to be HIV-positive at the end of 2024, with 65% in the African region [
1]. South Africa ranks among the countries with the highest prevalence, with a national prevalence of 18.8% among adults aged 15–45 years old [
2]. Before the era of antiretroviral therapy (ART), HIV reduced the quality of life and was associated with high morbidity and mortality worldwide [
3]. The widespread access to ART has significantly improved the quality of life, allowing HIV-positive individuals to live longer [
4].
In South Africa, ART was introduced in 2004 and improved the quality of life and life span of those infected [
5]. Women were previously discouraged from having children due to safety concerns about the transmission of HIV to their offspring [
6]. However, with ART widely available, they can now bear children with minimal risk to themselves and offspring [
7]. Although ART has reduced the prevalence of vertical transmission, there are concerns of it contributing to cardiovascular diseases through the promotion of cardiovascular risk factors [
8].
Cardiovascular risk factors such as obesity, dyslipidaemia, hypertension, insulin resistance, and renal dysfunction are major contributors to systemic endothelial dysfunction, a central driver of vascular complications [
9]. Obesity and insulin resistance increase the release of pro-inflammatory cytokines and plasma fatty acids, inducing oxidative stress and endothelial activation [
10]. Dyslipidaemia, in particular elevated low density lipoprotein cholesterol (LDL-c) and reduced high density lipoprotein cholesterol (HDL-c) contribute to the oxidation of lipids, directly injuring endothelial cells [
11]. Chronic hypertension places mechanical strain on vessel walls that disrupts the endothelial integrity, while renal dysfunction results in increased levels of uremic toxins, known to be strongly associated with vascular damage [
12,
13]. Together, these factors impair the synthesis of nitric oxide (NO), shifting endothelium to prothrombotic and pro-inflammatory state, increasing the susceptibility of macrovascular and microvascular damage [
14].
Endothelial dysfunction plays an important role in the development of retinal microvasculature impairment. Damaged endothelial cells in the retina diminish NO synthesis, limiting vasodilation and impairing autoregulation of retinal blood flow, thereby promoting retinal microvascular dysfunction and localised ischaemia and the development of cardiovascular diseases [
15,
16]. The standardised parameters of retinal vessel calibre include central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) derived from fundus photographs. CRAE and CRVE reflect the average diameter of retinal arterioles and the average of retinal venules, respectively [
17]. These indices are used as non-invasive markers of systemic microvascular health. The ratio of CRAE to CRVE, which is the arteriolar venular ratio (AVR), integrates both into a single indicator of retinal microvascular status, with lower values indicating the narrowing of arterioles or the widening of venules, which may indicate retinal microvascular dysfunction and potential risk for the development of cardiovascular diseases [
18].
Although cardiovascular risk factors such as hypertension, dyslipidemia, obesity, and insulin resistance are well-known contributors to vascular dysfunction, there is little evidence on their predictive potential for impaired retinal microvascular health, especially in pregnant women infected with HIV on ART. Therefore, this study aimed to assess the effect of ART and HIV on cardiovascular risk factors in predicting retinal microvascular impairment in HIV-positive pregnant women in Mthatha, South Africa.
4. Results
A total of 78 pregnant women (25 HIV-positive and 53 HIV-negative) were recruited into the study. Pregnant women from the HIV-positive group were older (
p < 0.05) than their HIV-negative counterparts. Weight, height and WC were similar (
p > 0.05) between the two groups (
Table 2).
SBP and HR were similar between the HIV-positive group and the HIV-negative group (
p ≥ 0.05), while DBP and MAP were higher in the HIV-positive group (
p ≤ 0.05). Moreover, HIV-positive pregnant women had increased cfPWV (
p ≤ 0.05) compared to their HIV-negative counterparts, whereas FMS and ABI were comparable (
p > 0.05) between the two groups. The UtA was higher in the HIV-positive group (
p ≤ 0.05). The HIV-positive group had increased levels of ADMA, whereas HEMS1 was similar between the HIV-positive and HIV-negative groups. The uCr, uALB and uACR were similar between the two groups (
p > 0.05). Lipid parameters such as TC, TG and HDL-c were comparable between the HIV-positive group and HIV-negative group (
p > 0.05). However, LDL-c was higher in the HIV-positive group (
p ≤ 0.05) (
Table 3).
The CRAE and CRVE were similar between the two groups (
p > 0.05), while AVR was higher in the HIV-negative group (
p ≤ 0.05) (
Table 4).
The HIV-positive group had a higher prevalence of pre-hypertension/hypertension (pre-HT/HT) compared to the HIV-negative group (
p < 0.05). Hypercholesterolaemia, Hypertriglyceridaemia and low HDL-c were comparable between the HIV-positive group and the HIV-negative group (
p > 0.05). However, high LDL-c was prevalent in the HIV-positive compared to the HIV-negative group (
p < 0.05). The HIV-positive group and HIV-negative group had similar high cfPWV and high FMS (
p > 0.05). Low ABI was prevalent among the HIV-positive group compared to the HIV-negative group (
p < 0.05) (
Table 5).
The relationship between retinal microvascular function and macrovascular function is presented in
Figure 1. The DBP correlated positively (
p ≤ 0.05) with CRVE in the HIV-positive group. Further, MAP had a positive correlation (
p ≤ 0.05) with CRVE in the HIV-positive group. A positive correlation (
p ≤ 0.05) was observed between cfPW and CRVE in the HIV-positive group. There was a negative correlation (
p ≤ 0.05) between urinary creatinine and AVR in the HIV-positive group.
Increased DBP, cfPWV, ABI, and LDL-c were likely to predict significant (
p < 0.05) reduction in AVR in HIV-positive pregnant women. Moreover, increased HDL-c predicted the likelihood for significant (
p < 0.05) reduction in AVR in HIV-positive pregnant women (
Table 6). These results suggest cardiovascular risk factors to predict microvascular dysfunction defined by reduced AVR in HIV-positive pregnant women on ART.
An association (β = 1.43 (95%CI = 0.24:2.63),
p = 0.022) was observed between DBP and CRVE in the HIV-positive group. The MAP in the HIV-positive group also showed a positive association (β = 1.26 (95%CI = 0.20:2.33),
p = 0.023) with CRVE. No significant association was observed between CRVE and cfPWV in both groups (
Table 7). These findings suggest DBP and MAP to predict increased CRVE in HIV-positive pregnant women on ART.
5. Discussion
The present study investigated the effect of HIV and ART on cardiovascular health to predict retinal microvascular impairment in pregnant women. Macro-cardiovascular riskparameters, including DBP, cfPWV, ABI, HDL and LDL-c were significant predictors of retinal microvascular dysfunction in pregnant women infected with HIV.
Pregnancy is a physiological state characterised by increased cardiovascular demand and endothelial activation [
31]. Exposure to HIV and ART before or during pregnancy, both of which have been linked to heightened cardiovascular risk, could accelerate vascular dysfunction in this population [
32,
33]. The adaptation of the maternal vascular function during pregnancy is important to increase the flow of blood through the uteroplacental unit to meet the requirements for foetal development. The inability of the maternal circulation to adjust can lead to microvascular complications [
34]. To better understand the vascular alterations among pregnant women in the present study, vascular function was assessed comprehensively using a combination of circulating biomarkers and hemodynamic techniques.
ART has been reported to cause damage in the endothelium of the placenta and blood vessels, leading to endothelial dysfunction, which may lead to macrovascular damage or dysfunction. ADMA, an inhibitor of NO production has been reported as one of the primary indicators of endothelial dysfunction, demonstrated by its ability to decrease vasodilation [
35]. In the present study, HIV-positive pregnant women on ART had significantly higher levels of ADMA compared to HIV-negative pregnant women. Similar finding was observed in a study carried out in Austria that reported high levels of ADMA among HIV-positive patients [
36]. A study documented that HIV causes endothelial dysfunction through chronic inflammation and consequent buildup of ADMA [
37]. Impaired vasodilatory capacity resulting from endothelial dysfunction reduces the ability of blood vessels to dilate, promoting arterial stiffness [
38]. The speed of the pressure wave along the arterial wall, called pulse wave velocity, can be used to assess arterial stiffness [
39]. The pulse wave travels at a low speed in a compliant arterial wall. The reflection wave also travels slowly to the aorta, thus augmenting the diastolic blood pressure. However, in arterial stiffness, the pressure wave travels at a higher speed, and the reflected pressure wave also travels to the aorta quickly, augmenting the systolic blood pressure [
40]. HIV-positive pregnant women had a higher cfPWV compared to the HIV-negative pregnant women in this study. Our finding concurs with a study carried out in the United Kingdom, which reported that aortic stiffness was increased among HIV-positive patients [
41].
Arterial stiffness impairs the ability of the endothelium to detect and respond to mechanical pressures, thereby compromising the integrity of the endothelial barrier, permitting LDL-c to penetrate the vessel wall. This forms a vicious cycle of stiff arteries and vascular injury [
42]. In the present study, HIV-positive pregnant women on ART exhibited increased levels of LDL-c, suggesting vascular damage due to ART. This finding aligns with a study carried out in Turkey that reported significantly increased levels of LDL-c, TC, and triglycerides among the HIV-positive patients compared to the HIV-negative group. ART has been documented to disrupt lipid metabolism, particularly elevating TG levels and decreasing HDL-c [
43]. In the present study, a high prevalence of low HDL-c was observed among the HIV-positive group. Certain antiretroviral therapies are linked with endothelial dysfunction and alterations in lipid profiles [
44]. Together, these vascular changes increase vascular resistance and eventually lead to the development and progression of hypertension [
45]. A study conducted in the Western Cape, South Africa, reported a high prevalence of de novo hypertensive disorders among pregnant women infected with HIV compared to those without HIV [
46]. In this study, a high prevalence of pre-hypertension or hypertension was observed among HIV-positive pregnant women compared to HIV-negative pregnant women. This finding suggests that HIV-positive pregnant women are at heightened risk of developing hypertensive complications such as pre-eclampsia. High blood pressure can reduce blood flow to the placenta, elevating the risk of pregnancy outcomes such as foetal growth restriction and preterm birth, among others [
47]. Uterine artery Doppler is an accurate method for assessing uteroplacental resistance to blood flow [
48]. In this study, the maternal UtA PI was significantly higher in the HIV-positive group. A study reported that some ART could directly contribute to the placental damage, uteroplacental pathology and maternal malperfusion [
49,
50]. Impaired vascular function can limit blood flow to the tissues and elevate damage to the end organs [
51].
Microcirculation through microvascular vessels plays a role in delivering nutrients and draining blood from all tissues and organs in the body. Because the retina and other end organs, including the brain and kidney, have similar structural characteristics and functional properties, the retinal microvascular vessels provide distinct and easy visualisation to assess human health and disease of the human microcirculation [
52]. Mitochondrial toxicity resulting from ART administration may affect the retinal pigment epithelium, resulting in retinal vessel damage or vascular dysfunction [
53,
54]. ART and viral load have been reported to decrease the tone of the retinal vessels [
55]. A study conducted in Cape Town, South Africa, reported that decreased retinal arteriolar diameter was associated with the duration of ART use and viral load [
56]. In this study, both the CRAE and CRAE were similar between the two groups. However, AVR was lower in the HIV-positive pregnant women on ART, suggesting that ART could induce vascular damage and dysfunction of the retina. Reduced AVR has been documented to be a predictor of cerebral atrophy, stroke and other cardiovascular complications in adults [
57]. A study carried out in Singapore also found decreased AVR among HIV-positive patients [
58].
Macrovascular and microvascular dysfunction are both independent but related predictors of cardiovascular events [
59]. A study reported that wider retinal venular was independently associated with hypertension [
60]. The DBP, MAP and cfPW positively correlated with CRVE among HIV-positive pregnant women on ART in this study. This correlation implies that small microvascular vessels and macrovascular vessels are affected by similar pathophysiological processes in the HIV-positive pregnant women on ART. A negative correlation was observed between uCr and AVR among the HIV-positive group on ART implying increased uCr is associated with reduced AVR. This finding suggests a link between renal dysfunction and retinal microvascular impairment. Retinal microvascular changes often indicate systemic endothelial impairment, a known effect of both ART and HIV [
61].
Cardiovascular risk factors, such as DBP, were shown to predict microvascular dysfunction, revealed by decreased AVR in the HIV-positive pregnant women on ART. These findings support the notion that increased BP contributes to elevated vascular resistance and microvascular impairment [
62]. In addition, markers of peripheral resistance and arterial stiffness, ABI and cfPWV, respectively were associated with lower AVR, suggesting that macrovascular alterations related to cardiovascular risk may negatively affect microvascular function [
63,
64]. High levels of LDL-c, which are known to promote atherosclerosis, emerged as a significant predictor of low AVR in this study. LDL-c has been reported to intensify microvascular damage in HIV-positive individuals [
65]. Overall, these findings suggest a potential link between cardiovascular risk factors and microvascular impairment in HIV-positive pregnant women on ART, highlighting the need for comprehensive cardiovascular monitoring to improve pregnancy outcomes in this population.