Pattern of complications and anatomical risk factors for atherosclerosis among black Kenyans

Abstract

Atherosclerotic diseases are emerging major health challenges in Kenya. Data on their patterns and anatomical risk factors vary between countries and populations and are important for informing appropriate management and prevention strategies, but are generally scarce from Kenya. The aim of this study was, therefore, to describe the pattern of complications and anatomical risk factors for atherosclerosis among black Kenyans. The study was done in two phases: Prospective and retrospective. Prospective autopsy examination was undertaken to describe the profile of cardiovascular causes of death including histomorphometry to determine intimomedial thickness, luminal stenosis and diameters, and look out for features of atherosclerosis. Cadaveric dissection and measurements were done to establish branching patterns, bifurcation angles, bifurcation area ratios and lengths of common carotid (CCA), left coronary (LCA), common femoral (CFA) and proximal renal arteries (PRA). Retrospective analysis of records from Kenyatta National Hospital for patients with aneurysm, stroke, myocardial infarction, peripheral vascular and hypertensive renal disease from January 1999 to December 2011 was done for anatomical localization, age and gender distribution, and comorbidities. Data were analysed using the Statistical Package for Social Sciences (SPSS) for windows version 17.0. Descriptive statistics were applied to determine frequencies, means and anges and standard deviations of the studied variables. Data were presented using tables, graphs, pie charts, macrographs and micrographs. Autopsy examination of 1200 cases of natural deaths revealed that cardiovascular disease caused 236 (19.7%) of them. Of these, 102 (43.2%) were atherosclerotic. Complications of atherosclerosis were the cause of 102 (8.5%) of all deaths. The most common complications included myocardial infarction (40; 16.9%), cerebral aneurysms (36; 15.3%), and aortic aneurysms (26; 11.0%). Mean age was 43.2 years, peaking at 40 – 60 years. Fifty two (51%) of the atherosclerotic diseases occured before 50 years. The male: female ratio was 1.5:1. Atherosclerotic plaques, occlusive intimal hyperplasia and severe intimal hyperplasia were present in 20 (9.4%), 34 (16%) and 53 (24.9%) of individuals respectively. Retrospective patient data analysis revealed that aneurysms occured most commonly in the infrarenal aorta, femoral and posterior communicating arteries. Stroke occured at mean age of 58.4 years, affected mainly the territory of middle cerebral artery more commonly in women than in men. Coronary atherosclerosis occured most commonly in the left anterior descending coronary artery (LAD) causing myocardial infarction at a mean age of 56.8 years, more frequently in men than in women. Peripheral vascular disease occured at a mean age of 60.5 years, more commonly in men. Femoral artery was the most commonly affected site. Atherosclerosis of proximal renal artery was the cause of end stage renal disease in 4 out of 114 (3.5%) of cases of hypertensive renal disease. The most frequent comorbidities were hypertension, diabetes mellitus, obesity, dyslipidemia, smoking and infections. From cadaveric dissection of 208 specimens, the highest proportion of variant branching patterns was in the left coronary (94; 45.2%), followed by common carotid (86; 41.3%), renal (123; 40.3%) and femoral (58; 27.8%) arteries. Mean bifurcation angles for respective arteries were 24.10 (common carotid); 24.70 (femoral); 61.90 (left coronary). Mean implantation angle of the renal artery was 940. Mean length of left coronary, femoral and renal arteries was 8.45 mm, 43.1 mm and 31.0 mm respectively. Mean bifurcation area ratio of common carotid artery was 1.05 with 74 (35.6%) of cases being above the optimum of 1.2. Mean intimomedial thickness of the common carotid, left anterior descending, common femoral and renal arteries was 0.86mm; 0.332 mm, 0.76 mm and 0.46 mm respectively. The IMT increased with number of branches, bifurcation area ratio and bifurcation angle, and decreased with arterial length. It was higher in males. Mean luminal arterial diameter for the LAD, CCA, CFA and PRA were 2.72 mm; 7.86 mm; 8.4 mm and 3.6 mm respectively. Diameter increased with number of branches and was higher in males. In conclusion, cardiovascular disease causes nearly 20% of deaths with atherosclerosis constituting over 8% of overall mortality. Myocardial infarction was the most common condition, overlapping with infectious and nutritional conditions. Complications of atherosclerosis frequently occur in individuals aged ≤ 40 years, in males more than females. Comorbidities included modifiable risk and lifestyle factors as well as infections and inborn conditions. Anatomical risk factors comprising abnormal branching patterns, wide bifurcation angles, short arterial stems, suboptimal bifurcation area ratios and high intimomedial ratios existed in over 15% of the population. These observations indicate that atherosclerosis is a significant problem in the black Kenyan population and vulnerability starts from birth. Control measures should commence from early in life