CARDIOVASCULAR JOURNAL OF AFRICA • Volume 35, No 1, January – April 2024 10 AFRICA by Elias et al., where type 2 diabetes mellitus status was linked with a significantly higher PWV.21 Studies have shown increased stiffening of arteries in diabetes, and this suggests that it might be due to endothelial dysfunction, low-grade inflammation and oxidative stress, as well as the formation of advanced glycation end-products in the vessel wall, causing cross-linking of collagen molecules and loss of elasticity.22 Continuous increases in blood pressure also stimulate matrix synthesis, causing subsequent elevation in vascular thickness and structural stiffening.23 In addition, chronic hyperglycaemia and hyperinsulinaemia elevate the local activity of the renin–angiotensin–aldosterone system and the expression of angiotensin type I receptors in the vascular tissue, resulting in the development of wall hypertrophy and fibrosis.24 A study by Osuch et al. showed that there was an improvement in arterial elasticity in black patients on angiotensin converting enzyme inhibitors (perindopril 4 mg).9 It would be warranted to investigate further the influence of angiotensin converting enzyme inhibitors on arterial elasticity in obese populations. According to previous studies, Aix can be influenced by an individual’s age, gender and heart rate.21 Our study showed that in obese black participants, Aix was significantly correlated with age, aortic SBP, and radial SBP and DBP, indicating that age and increased BP might lead to an increase in arterial stiffness (Table 2). Increased BP upsurges afterload and the oxygen demand of the myocardium and contributes to left ventricular hypertrophy. This leads to increased arterial stiffness, leading to an imbalance between myocardial oxygen demand and supply.2 A study by Mittchell et al. showed that a healthy individual with no evidence of CVD and low burden of risk factors had age-related increased aortic stiffness.25 Boutouyrie and Vermeersch showed that the enhanced influence of ageing with high BP was gradual, the increase in PWV with BP was more prominent as the subjects got older and that the correlation between PWV and age was highly significant.26 This might be due to the remodelling of the middle tunica, comprising the fragmentation of elastin and its replacement with collagen fibres and calcium deposition, resulting in loss of elasticity and decreased arterial compliance.25,26 The results of this study concur with a number of studies where arterial stiffness increased with increasing age.2,22 The results showed that age was directly correlated with PWV and Aix (Table 2) and that PWV and Aix increased with increasing age (Table 2, Figs 1 and 2). There were limitations to this study. Due to the small sample size, a separate analysis regarding the effect of different antihypertensive and antidiabetic medication on arterial stiffness could not be investigated. The small sample size impacted negatively on the power of the test and therefore it is proposed that the research should be repeated with a larger sample. Anthropometric measurements such as body circumference and waist-to-hip ratio were not done. Conclusion Obese black patients had higher PWV, indicating stiffer arteries and therefore higher risk for CVD. The risk of CVD in the obese patient without additional diseases was increased by 50.7%. Furthermore, aging, increased BP, type 2 diabetes mellitus and increased cholesterol level contributed further to arterial stiffening in these obese patients. The presence of concomitant diseases (diabetes and hypertension) increased arterial stiffness by 11.4% and therefore further increased the risk of CVD by 35.1%. References 1. Yuong OS. Arterial stiffness and hypertension. Clin Hypertens 2018; 24(17): 1–3. 2. De Oliveira AR, Lima Santos PC, Bortolotto LA, Mill JG, da Costa Pereira A. Arterial stiffness: pathophysiological and genetic aspects. Int J Cardiovasc Sci 2017; 30(5): 433–441. 3. O’Rourke MF, Junichiro H. Mechanical factors in mechanical arterial aging: A clinical perspective. J Am Coll Cardio 2007; 50(1): 1–13. 4. Seifalian AM, Filippatos TD, Joshi J, Mikhailidis DP. Obesity and arterial compliance alterations. Curr Vasc Pharmacol 2010; 8: 155–168. 5. Pal S, Radavelli-Bagatini S. Association of arterial stiffness with obesity in Australian women: A pilot study. J Clin Hypertens 2013; 15(2): 118–123. 6. Elias M, Dore A, Davey A, Abhayaratna W, Goodell A, Robbins M. Norms and reference values for pulse wave velocity: one size does not fit all. J Biosci Med 2011; 1(4): 1–9. 7. Obara S, Hayashi SH, Akihirob M, Masahiroa K, Shin-ichirob. Correlation between augmentation index and pulse wave velocity in rabbits. J Hypertens 2009; 27(2): 332–340. 8. Paiva AMG, Mota-Gomes MA, Brandão AA, Silveira FS, Silveira MS, Okawa RTP, et al. Reference values of office central blood pressure, pulse wave velocity, and augmentation index recorded by means of the Mobil‐O‐Graph PWA monitor. Hypertens Res 2020; 43: 1239–1248. 9. Osuch E, Du Plooy WJ, Du Plooy SH, Böhmer L. Effects of perindopril on pulse-wave velocity and endothilin-1 in black hypertensive patients. Cardiovasc J Afr 2012; 23(7): 396–399. 10. Lehman ED, Watts GF, Fateni-Langroudi B, Gosling RG. Aortic compliance in young patients with heterozygous familial hypercholesterolaemia. Clin Sci 1992; 83: 717–721. 11. Naijar S, Scuteri A, Shetty V, Wright GJ, Muler CD, Fleg LJ, et al. Pulse wave velocity is an independent predictor of longitudinal increases in systolic blood pressure and of incident hypertension in the Table 2. Multivariable linear regression analysis for PWV and Aix in the study participants (n = 110) Variables Aix (± SE) p-value PWV (± SE) p-value Age 0.156 ± 0.07 0.04* 0.046 ± 0.021 0.031* Aortic PP 0.11 ± 0.132 0.402 –0.073 ± 0.044 0.101 Radial PP –0.276 ± 0.161 0.089 0.079 ± 0.534 0.15 MAP –0.041 ± 0.170 0.081 –0.067 ± 0.56 0.234 Heart rate 0.398 ± 0.081 < 0.0001* 0.060 ± 0.027 0.03* Aortic SBP 1.595 ± 0.022 < 0.0001* 0.228 ± 0.073 0.003* Aortic DBP 0.920 ± 0.599 0.135 –0.174 ± 0.197 0.383 Radial SBP –1.134 ± 0.214 < 0.0001* –0.097 ± 0.07 0.017 Radial DBP –1.449 ± 0.524 0.009* –0,165 ± 0.178 0.357 BMI –0.045 ± 0.124 0.714 0.07 ± 0.041 0.079 HbA1c –0.013 ± 0.172 0.940 0.192 ± 0.056 0.0009* TC –1.929 ± 1.67 0.251 0.544 ± 0.554 0.329 LDL-C 2.34 ± 1.73 0.183 –0.201 ± 0.577 0.728 TG –1.51 ± 0.827 0.191 –0.124 ± 0.284 0.664 HDL-C 6.92 ± 3.226 0.054 –0.706 ± 1.07 0.512 MAP, mean arterial pressure; PP, pulse pressure; SBP, systolic blood pressure; DBP, diastolic blood pressure; BMI, body max index; HbA1c, glycated haemoglobin; TC, total cholesterol; LDL-C, low-density lipoprotein cholesterol; HDL-C, high-density lipoprotein cholesterol; TG, triglycerides; SE, standard error; Aix, augmentation index; PWV, pulse-wave velocity. *p < 0.05.
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