PRINCIPALES CRÍTICAS A LA TEORIA DE PIAGET.

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group. In hypertensive elevated blood pressure level can cause injury/damage to the endothelium of blood vessels with subsequent thickening of intima media complex via medial hypertrophy,^55,61 a process specifically related to the disease. This thickening of the arterial wall is probably an adaptative mechanism to compensate for the persistent increase in blood pressure levels.⁵⁶ and the thickening of the vessel wall have been demonstrated in vivo and vitro.⁴⁸ This effect is not seen in normotensive subjects whose blood pressure levels are essentially normal, and thus normal CIMT is present in this group.^52,53,55 Therefore increase in blood pressure has a significant effect on the intima media thickness.

In this study the overall mean CIMT of 0.89mm±0.13 in hypertensive subjects were higher compared to values from previous studies, Honzikova⁵³ and Plavnik⁵⁶ recorded 0.60 mm and 0.67mm respectively and Lemne⁶⁰ in Sweden had an overall value of 0.73mm. On the contrary, the overall mean CIMT in normotensive subjects in this study was lower than 0.69mm obtained in study by Lemne et al ⁶⁰ but higher than 0.51mm and 0.54mm recorded by Honzikova⁵³ and Plavnik⁵⁶ respectively. The differences in CIMT observed in various studies in both hypertensives and normotensives could be due to sampling methods, sampling size, and racial differences. The sample size in this study was comparably larger than in other studies.^53,56,60 Differences in life styles, diet and social habits, for instance high alcohol intake as well as chronic intake of potato chips in the study environment (Jos) is known to induce a proinflammatory state which is a risk factor for atherosclerosis⁵⁵ and may be responsible for the differences in the CIMT observed in this study and other studies.

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In this study, the method used at arriving at CIMT value involved taking three measurements 1cm proximal to right and left carotid bulb and the mean value of the three measurements were recorded for each side; this was different from the method employed in some other studies.^56,60 This method is simple, reliable, and reproducible.

There is minimal inter and intra observer error.⁶² Using this method allows rapid identification of the target area and ensures that an identical area is assessed on follow-up.⁶² Certain infections such has viral hepatitis and human immunodeficiency virus infection have been shown to be associated with increased CIMT probably due to presence of proinflammatory cells which are risk factor in artherogenesis.^55.61

Bilaterally, there was a noticeably higher right and left CIMT value in hypertensives compared to normotensives (0.89mm±0.13 and 0.89mm±0.18 Vs 0.61±0.10mm and 0.62mm±10) in this study. Many other studies shows similar trend, Sharma⁵¹ recorded 0.968mm and 0.969mm vs 0.551 and 0.555mm; Adaikkappan⁵² recorded 1.01mm and 1.09mm vs 0.74mm and 072mm; Umeh⁵⁴ recorded 0.751mm±0.129 and 0.756mm±0.130 vs 0.670mm± 0.107 and 0.638mm±0.088; Okehialam⁵⁵ recorded 93mm±0.21 and 0.93mm±0.15 vs 0.91mm±0.17 and 0.91mm±0.13; Planvnik⁵⁶ recorded 0.67mm±0.13 and 0.62±0.09 vs 0.54mm±0.09 and 0.52mm±0.11 for hypertensives and normotensives respectively.

The mean CIMT value in the left CCA was higher than the right CCA (0.62mm±10 Vs 0.61mm±10) in normotensive group of patients studied. Although, this findings was not statistically significant (P=0.18). This result was consistent with the study by Sharma⁵¹ but contrary to findings in other studies.^52,54 There was no difference in the measured

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CIMT value between the left and right CCA in hypertensive group (0.89±0.13 Vs 0.89±0.13) and this finding is similar to those in a study in Jos by Okeahialam.⁵⁵ However some other studies showed a difference in values between the measured left and right CIMT with the left CIMT value higher than right.^51,52,54 while another study⁶⁰ showed right CIMT value to be higher than the left. In this study, equal value of CIMT observed on both CCA for hypertensive and the higher value of CIMT recorded in the left CCA in normotensive, are contrary to the findings of Lemme⁶⁰ who recorded higher CIMT value in the right CCA for both hypertensive and normotensive subjects. The reason for such differences between IMT of right and left common carotid artery sides are unknown. However, the left common carotid is a direct branch of the aorta while right common carotid results from division of brachiocephalic trunk. Therefore it is possible that dissimilarities have existed in the arterial growth between both arteries and/or that flow mediated mechanical forces applied to carotid wall differ between the two sides.⁶⁷

The mean CIMT value of male and female hypertensives were higher than the mean CIMT value of male and female normotensive (male and female hypertensives CIMT values were 0.92mm vs 0.87mm, while in normotensive males and females CIMT value were 0.62mm vs 0.61mm. In both groups males have a higher CIMT value than females. This relationship was not statistically significant (Hypertensive P=0.11 and Normotensive P=0.70). This finding was consistent with other studies^38,54,61 and may be explained by the sex variation in the development of artherosclerosis. Males have a higher chance of developing artherosclerosis more often than women^37,38, although the

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reasons are not known but may be due to the fact that males are more prone to psychological and environmental stress than females.^38,55

There was progressive increase in CIMT from age 18 years to 70 years in hypertensive and normotensive groups of patients. The CIMT values in hypertensive subjects were higher than CIMT value of normotensive subjects in each age group. Most of the studies reviewed also consistently showed with increased CIMT with age.51,53,54,56,61 This study also showed that age has a strong correlation with CIMT values recorded in both hypertensive and normotensive subjects investigated (Pearson correlation 0.35 and 0.88 in hypertensives and normotensives respectively). The increase in mean CIMT with age in normotensive subjects could probably be due to specific effect of aging on the arterial wall or probably be due to exposure to risk factor not measured or captured in this study. In hypertensives, higher CIMT value with age could probably be due to the combined effect of increase blood pressure levels and aging process on the intima media. Also the impact of blood pressure levels on the intima media has been considered as an accelerated form of aging and hypertensive patients develop aging process in their arterial walls earlier in life than normotensives.

There was also progressive increase in mean CIMT with BMI in normotensive subjects.

This was statistically significant. Mean CIMT correlated positively with BMI in normotensive but negatively in hypertensive subjects. Similar finding was demonstrated in the studies by Honzikova and Planvik.^53,56 BMI has been shown to influence the CIMT but the role of BMI in arterial wall thickening is poorly understood and its influence is probably independent of age.⁴⁹

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Most studies have suggested that age is the strongest determinant of carotid wall thickness and systolic blood pressure has been considered as a secondary determinant in hypertensive subject.^9,48,57

In this study, CIMT correlated positively with systolic and diastolic blood pressure of hypertensive patient. (Pearson correlation for SBP is 0.22 and DBP 0.21). This was consistent with several other studies^52,53,56 despite differences in the methodology employed in measurement of blood pressure. While blood pressure was taken at presentation in this study; other studies used 24hrs systolic and diastolic blood pressure measurement method.^53,56 Also, CIMT was noticed to increase with increasing blood pressure levels.

A plaque is defined as a focal structure arising from the intima media layer of the arterial wall and encroaching into the arterial lumen.²⁹ Plaques are sometimes found in the wall of the vessel of hypertensive patients. Carotid Plaques were seen in the vascular wall of six hypertensive patients (3%) in this study, while none was noted in the CCA of normotensive subjects. These plaques were more evident in right CCA. This finding is similar to what was recorded by Lemne⁶⁰ et al study where they also recorded higher number of plaques in hypertensives which were also evident in the right carotid arteries. Umeh⁵⁴ et al in Ibadan also recorded a higher number of plaques among hypertensive subjects.

70 CONCLUSION

This study has shown that there is a significant difference in the CIMT of hypertensive compared to normotensive subject. Higher values of CIMT were seen in hypertensive subject compared to normotensive from age groups 18-70 years. Age, sex, BMI and blood pressure levels have significant effect on CIMT of hypertensive patient. CIMT increases with increasing blood pressure levels and advancing age in hypertensive subjects. It also revealed that CIMT increases with age and with increasing BMI in normotensives. Male hypertensives had higher CIMT than the female counterpart. B-mode ultrasound is a reliable, readily available, cheap and noninvasive imaging modality that is useful in the management of hypertension.