DESARROLLO DEL TALLER Nº 3.

This study showed that despite a wide spread advanced atherosclerosis (types IV-VI), the coronary arteries appeared to be protected against the lesion as there was only a case (0.5%) of type IV atherosclerosis out of the 202 coronary arteries examined. In 2001, Falase et al⁷⁰ showed that incidence of myocardial infarction was still relatively low in Nigerians suggesting that Nigerians are at an early stage of ‘epidemiologic transition’. Rotimi et al^{71, 72} examined cases of sudden unexpected deaths over a ten year period of which 79 deaths were found to be cases of sudden cardiac deaths. Out of these, 20% had coronary atheroma of less than 50% lumina occlusion suggesting that coronary artery disease (CAD) may be on the rise in Nigerians. Akinboye et al⁷³ examined the trend in coronary artery disease and associated risk factors in sub-Saharan Africans by conducting a Medline search of English language articles on CAD in Africans from 1966 to 1999. They concluded that there is a gradual upward trend in the prevalence of CAD but that it is unclear whether the increase was as a result of improved diagnostic ability or a true increase in the prevalence of CAD. These findings are contrary to the results of this study. This is so because unlike the index study, only those with clinical or radiological evidence of CAD were studied by the Akinboye group.

Most of the lesions seen in this study were in the early stage (72.4%). This is in agreement with the work done by Williams⁷ who examined coronary atherosclerosis in autopsy cases Ibadan and showed that 71% had early lesions. In Ethiopia, Maru,³¹ in his work on atherosclerosis in unselected autopsy cases had similar results. Yazdi et al²⁸ had a different finding when they examined prevalence of atherosclerotic plaques in autopsy cases in which

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case early lesion was found to be 40%. Prevailing risk factors such as diet, sedentary life style, tobacco exposure etc. were likely the reason for this difference.

This study demonstrated atherosclerosis in all the age groups. There was a gradual increase in severity of atherosclerosis with increasing age. The advanced lesion attained a peak in the 6^th decade in both abdominal aorta and basilar artery. The only case of advanced coronary artery atherosclerosis was seen in the 8^th decade. The detection of early atherosclerosis in this study as seen in the age group between 14 and 19 years is consistent with a model shown by McGill et al⁷⁴ in their work on origin of atherosclerosis which concluded that atherosclerosis began relatively early in life (age 10–20 years) with deposition of fatty streak, progressing (age 20–

30 years) to the fibrous plaque, and that further advances seen from ages 30–50 years was due to age but also the action of traditional risk factors such as cigarette smoking, unfavourable blood lipid, etc. While there are few local studies demonstrating the mean ages of different atherosclerotic type, Rotimi at el^{71, 72} in Ile-Ife showed the mean age for advanced lesions among hypertensive to be 53.7±11.2. The age in Ile-Ife’s study is lower than the result obtained this study because only hypertensives with heart disease were studied and these have been shown to develop advanced lesion earlier than the general population. In UCH Ibadan, Erete et al⁷⁵ in their autopsy study of prevalence and severity of atherosclerosis in extra-cranial carotid artery showed the mean age for advanced lesions to be age group above 60 years. This is in line with the index study as their study population was not limited to people with cardiac conditions alone, unlike the Rotimi et al study group.

In the index study males had more advanced disease when compared to females. Seventy-nine percent of advanced lesions were in males as compared to females with twenty-one percent of the advanced lesions. This difference was not statistically significant. This finding is consistent with the autopsy work done by Erete et al in Ibadan to demonstrate the prevalence and severity of atherosclerosis in extra cranial carotid artery in Nigeria in which

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30 autopsies were studied. They demonstrated that though males were affected by more severe types of the lesion than females, the difference was not statistically significant. A similar result was demonstrated by Thej et al⁷⁶ in India who examined atherosclerosis in coronary artery and aorta in a semi urban population. To date, the causes of this gender difference remain unclear. Such observations have produced considerable interest in the potential role of sex hormones in atherogenesis.⁷⁷

In this study, the abdominal aorta had more severe (type IV, V and VI) atherosclerosis than the basilar and the coronary artery. The high frequency of advanced lesions in the abdominal aorta as compared with the other vessels is thought to be as a result of its exposure to

haemodynamic turbulence because of the numerous arterial branches from the abdominal aorta.¹⁴

The coronary artery had the least advanced lesion with only a case of advanced lesion. This finding is not in line with the general teaching³⁶ that coronary arteries has more advanced lesions as compared with the circle of Willis. This teaching is however true in western climes but not in Nigeria as other investigators have shown that coronary atherosclerosis is low in this environment.^70,77

This study showed a significant association between hypertension and advanced atherosclerotic lesion in the abdominal aorta and basilar artery. Olusakin et al⁷⁸ evaluated some risk factors for atherosclerosis in the circle of Willis observed at autopsy in University College Hospital (UCH) Ibadan and found that hypertension had a significant association with atherosclerosis. Alexander in Atlanta USA reviewed published articles on atherosclerosis and hypertension and came to a conclusion that hypertension predisposes to and accelerates atherosclerosis.⁷⁹ Aram et al demonstrated the influence of hypertension on atherosclerosis by inducing hypertension in Watanabe rabbits. Three months after inducing

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hypertension, 77.0% of the rabbits have developed significant atherosclerosis.⁸⁰ This is in line with this study in which 98.7% of the hypertensives had advanced aortic atherosclerosis.

There was also a strong association between diabetes mellitus and atherosclerosis in the index study. Olusakin et al. had a similar result in his work on autopsy cases. Chen et al.⁸¹ in their study on the association between metabolic syndrome, diabetes mellitus and atherosclerosis concluded that diabetes mellitus and metabolic syndrome are independent associated with an increased risk of atherosclerosis. The quoted works above along with the index study have been able to show that diabetes mellitus and hypertension are important factors among others in the pathogenesis of atherosclerosis. The index study showed a strong association between the development of advanced lesions with hypertension and diabetes mellitus. The duration of exposure to these risk factors have a direct relationship with the severity of the lesion.²⁸ The duration of exposure of blood vessels to risk factors was however not documented in this study because most of the cases employed were brought in dead with little or no history.

There were however strong evidence in keeping with long standing or uncontrolled hypertension/diabetes mellitus (atherosclerosis, organomegally, benign nephrosclerosis etc.).

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