THE DISTRIBUTION AND SEVERITY OF ATHEROSCLEROSIS IN ADULT NIGERIANS: A 12 MONTH PROSPECTIVE AUTOPSY STUDY

Abstract

Background & Objectives: Atherosclerosis is characterized by lesions in the intima called
atheromas (also called atheromatous or atherosclerotic plaques) that protrude into vessel
lumina. Atherosclerosis causes far more morbidity and mortality (roughly half of all deaths) in
the Western world than any other disorder but although ubiquitous in developed nations,
atherosclerosis is much less prevalent in Central and South America, Africa and Asia. The
composition of the plaque rather than the extent of luminal occlusion has been said to be of
more value in predicting ischaemic events. Factors such as hypertension, diabetes mellitus,
obesity and racial differences have been noted to affect the distribution and severity of
atherosclerotic lesions as well as their composition. The objective of this study was to assess
the severity and distribution of atherosclerotic lesions amongst Nigerians as well as document
the composition of atherosclerotic plaques seen in this population.
Materials and Methods: All patients aged 18 years and above who had post-mortems carried
out at the Department of Anatomic and Molecular Pathology, Lagos University Teaching
Hospital had their cerebral, coronary and descending aorta assessed for extent and severity of
atherosclerosis. Sections were taken from the coronary arteries and were histologically
examined using H&E and elastin van Gieson special stain. Immunohistochemistry was also
done using CD3, CD68 to highlight lymphocytes and macrophages. The data was analysed
using SPSS 20 and correlations were attempted between the age of the patient, history of
diabetes and hypertension, obesity and the severity and composition of atherosclerotic lesions

Results: A total number of 103 subjects were studied with 67 males and 36 females giving a
M:F ratio of 1.9:1. The age of the subjects ranged from 18 to 86 with an average age of 50.47
(SD=14.12) years. Grade 1 lesions were found in 100% of the aortas, Grade 2 lesions in 74%,
Grade 3 in 25%, Grade 4 in 8.7% and Grade 5 in 4%. The most severe occlusions were present
in the left anterior descending (LAD) coronary artery. The lumen of the LAD artery showed
occlusion ranging from 0 to 60% with an average of 13.40 (SD=13.40). Intimal xanthoma
lesions were the most common accounting for 48 (46.6%) of the atheromas seen. Intimal
thickening accounted for 33 (32.0%), pathological intimal thickening 10 (9.7%), fibrous cap
atheroma 6 (5.8%), while thin fibrous cap atheroma and fibrocalcific plaques accounted for 4
(3.9%) and 2 (1.9%) respectively. The age of the subject, BMI (Basal Metabolic Index), WHR
(Waist hip ratio) and a positive history of hypertension significantly affected the severity and
composition of atherosclerotic plaques.
Conclusion: From this study, the descending aorta was the most frequently and severely
affected vessel. The left anterior descending artery was the most affected of the coronary
arteries and the maximum extent of luminal occlusion seen was 60%. The cerebral vessels were
the least affected. Furthermore increasing age, obesity and hypertension all significantly
contributed to the occurrence and severity of atherosclerotic lesions. However, significant
correlation could not be found between a positive history of diabetes mellitus and
atherosclerotic lesions.

THE DISTRIBUTION AND SEVERITY OF ATHEROSCLEROSIS IN ADULT NIGERIANS: A 12 MONTH PROSPECTIVE AUTOPSY STUDY