Coronary artery pathology of 111 consecutive Nigerians

TRANSACTIONS OF THE

ROYALS~CIETV OFTROPICAL MEDICINE ANDHYGIENE (1986)

Coronary

artery

pathology

80, 923-926

of 111 consecutive

923

Nigerians

P. 0. OGUNNOWO’*, W. 0. ODESANMI’ AND J. J. ANDY’ Dept. of Medicine and Dept. of Pathology, University of Ife, Ile-Ife, Nigeria Abstract

A detailed study of the coronary arteries of 111 consecutive necropsies at Ile-Ife, Nigeria is reported. Coronary occlusive diseaseoccurred in eight (7.2%) subjects and involved <50% of huninal size in five, and ~50% of luminal size in three subjects. Previous medical history was available in four of eight subjects and all four had hypertension. All three subjects with >SO%luminal occlusion were hypertensive patients and professionals, one was additionally diabetic and a heavy smoker and serum cholesterol (available in one) was 250 mgiml. The mean age of the subjects with moderate and severe diseasewas 54 (range 35 to 71) years. Thus coronary occlusive diseaseamong Nigerians occurred in elderly, affluent and hypertensive patients exposed to Western diets and habits. Introduction

Our clinical study of symptomatic coronary heart diseaseand of myocardial infarction has revealed no significant increase in the prevalence of this diseasein Nigeria in the last one and a half decades(Ogunnowo & Andy, 1984, unpublished observations). However since nearly 75% of the lumen of an artery has to be occluded before severe symptoms and complications are manifested, this clinical study has not excluded some significant sub-clinical increase in severity of coronar$ atherosclerosis in Nigeria. Pathological-studies from South Africa (ISAACSON.19771 found a 13-fold increased incidenie of myocardial ‘infarction among black South Africans. A sizeable number of Nigerian urban elites are acquiring dietary habits, smoking habits and other predisposing factors to coronary artery disease.It was of interest to study the coronary pathology of Nigerians, and to compare the findings with those previously reported (WILLIAMS, 1971) in order to establish any changes in frequency and severity of coronary atherosclerosis. Subjects and Methods

The heartsexaminedwerefrom 111consecutiveautopsies at Ife during a period of fwo years.All heartswerefixed in 10%form01saline beforeexamination.The cardiacchambers and aortawere openedand washedin distilled wafer. Eachheart chamberwassystematicallyexaminedmacroscooicallv for mvocardialinfarction. Cut sectionsof susoected areas‘were siained with haematoxylinand eosin aid examined for infarction. After careful examination of the coronary ostia for occlusive lesions, the right and left coronaryarteriesand all their majorbrancheswerecarefully dissectedoff their beds.Sectionsof thesearteriesweremade approximatelyat 0.5 cm intervalsfor macroscopicexamination. Sectionsfor histological examinationwere taken at 1 cm intervals, exceptin diseasedarterieswhere the most severelyaffectedareawassectioned,stainedand studied.All sectionstaken were embeddedin paraffin or Carbowax. Multiple sections,7 p thick, weretakenfrom the par&in blocks and stained with haematoxylin and eosin. The preparedslides were examinedunder the microscope. For this study, the following characteristicswere looked for macroscopicallyand microscopically:fatty streakswere consideredflat or slightly raised internal lesions which containedelongatedcells and large ovoid cells filled with lipid droplets(ovoid foamcells);fibrousplaqueswereraised lesionscharacterizedby smoothmuscle cell proliferation, accumulationof connectivetissuefibresandmatrix andlipid deposition.

Complicatedlesionsincluded calcification,haemorrhage and ulceration.The lesionswerefurther classifiedasstreaks; mildly raised lesions which included fibrous lesions and streaks;moderatelesions which included complicatedlesions that occupiedless than 50% of the lumen size; and severe lesions which included complicated lesions that occupied50% or more of the lumen size. Results There were 111 cases (69 males and 42 females) ranging in age from 5 to 71 (mean 34.3) years. The distribution of all atherosclerotic lesions ranging from plaques to fibrous and complicated lesions affecting all the major coronary arteries are tabulated in Table 1. The distribution of moderate and severeCAD and the features of the affected patients are tabulated in Table 2. 32 129%) of all uatients studied had some degree of co;onar$ artery-pathology, but only eight (7.2%) had moderate to severe coronary occlusion (Fig. 1). In most of the patients the pathology did not progress beyond streak lesions. Of those with moderate disease(Table 2), one was known to have hypertension. All three patients with severe diseasehad hypertension but one of them was also a known diabetic and a heavy cigarette smoker. Two patients with severe coronary artery diseasehad three vessels disease but in the other only the left anterior descending artery was affected. Both patients with three vessels disease were professionals in the high income bracket, one of them in whom serum cholesterol was measuredhad a level of 250 mn%. and the other was a known diabetic and hype;tehsive patient. Discussion

This study found five cases with moderate and three cases with severe coronary atherosclerosis among 111 consecutive and unselected patients. One of the three severecaseswas complicated by myocardial infarction, but in the remaining two severe coronary atherosclerosis was an incidental autopsy finding. WILLIAMS (1971) from Ibadan, Nigeria, did not find a single casewith coronary thrombi in a study of 279 consecutive autopsies. FLORENTINet al. (1963) studied 161autopsied New Yorkers (106 males and 55 *Address for correspondence:Dr. J. J. Andy, Dept of Medicine, Collegeof Medical Sciences,University of Calabar, Calabar,Nigeria.

CORONARY

924 Table

l-Involvement

of coronary

arteries

ARTERY

PATHOLOGY

in relation

OF NIGERIANS

to age (minimally

raised to severe

41-50 51-60 60-70 71-80

lesion)

Percentageof patients in each decade

No. of cases with lesions

l-10 11-20 21-30 31-40

and complicated

No. of patients 5

LM+LAD -

LCX -

RCA -

:“o

-i 6 (1)

-i

7

23

ii!

4 ':'

5 :2)

:ij

4

2 \l’

3-k

3

‘:I

LM+LAD -

LCX -

RCA -

153 26.1

;6 13.0

73 13.0

22.2

27.8

;:;

G1 100

7s 100

75

100 33.3 33.3 1: 55.5 : ; 2: unknown 15.3 12.6 25.0 17 111 Total LM = Left Main CoronaryArtery, LAD = Left Anterior DescendingArtery, LCX = Left CircumflexArtery, RCA = tight Coronary Artery. Numbers in parenthesesrepresentthose with moderateor severedisease.

Table

Pharacteristics

of patients

with moderate

OccupaSex ation M Professional

Initials V.O.

Age 48

A.A.

50

F

Middle

O.L.

50

M

F.O.

35

F

Low income Middle

0.0.

66

M

J.A.

64

M

K.A.

52

M

1.0.

71

Low income -

and severe coronary

atherosclerosis

Se:F athero- Vessels

Known predisposing factor Diabetes, hypertension and smoking

Causeof death Seoticaemia ad pyelonephritis

sclerosis involved Severe RCA. LCX. LAD. No myo&dial infarction

Hypertension -

Hypertension with C.V.A. R.T.A.

Severe LAD, No myocardialinfarction Moderate LCX

Hypertension

Complications of childbirth

Moderate LAD

-

R.T.A.

Moderate RCA

-

R.T.A.

Moderate LCX

-

R.T.A.

Moderate RCA

Professional

Hypertension, Severe RCA, LCX, LAD, LM+ cholesterol myocardialinfarction 250 mg% M = Male, F = Female, R.T.A. = Road Traffic Accident, C.V.A. = CerebrovascularAccident, RCA = Right Coronary Artery, LCX = Left Circumtlex, LAD = Left Anterior Descending,LM = Left Main CoronaryArtery. M

females) matched for age and sex with 161 autopsied Africans, and found 28 casesof myocardial infarction among the American males and six casesof myocardial infarction among the American females. No infarcts were seenin any of the Africans. HIGGINSON & PEPPLER(1954), in a series of 1328 consecutive necropsies carried out at Beragwanath non-European hospitals, South Africa, over a period of five and a half years, found seven casesof coronary thrombosis or of myocardial infarction. BECKER(1946) found only one death due to coronary artery thrombosis among a seriesof 352 predominantly Bantu post-mortem cases over the age of 50 years. Compared with the findings of WILLIAMS (1971), the findings in this series indicate a significant

increase in complicated, coronary artery thrombotic lesions among Nigerians during the last 14 years. Our observations are similar to those of ISAACSON (1977) from South Africa, who did a retrospective autopsy analysis of cardiac pathology in 1959, 1960 and 1976, in one hospital in South Africa. He showed that the most dramatic alterations in the incidence of cardiac disorder among black South Africans occurred in the caseof myocardial infarction. Although the incidence of myocardial infarction was still very low among black South Africans compared with whites, he found that there was already a lffold increase in incidence of the diseasebetween 1959/60 and 1976. The only patient with moderate coronary atherosclerosisin our serieswho did not die from road traffic

925

a

Fig 1. Sectionsthrough coronaryarteriesof Nigeriansshowing: (a) mild complicatedcoronaryatheroscleroticlesion;(b) complicatedthromhoticlesionoccupyingless than 50%of luminai size;(c) complicatedthromhoticlesionoccupyinggreaterthan 50%of luminalsize;(d) total coronaryocclusionwith haemorrhageand recanahzation.

accident., was a known hypertensive. All three patients with severe coronary artery diseasehad hypertension, one of them was also diabetic and a heavy cigarette smoker. Two of the three with severedisease were males in the professional class and serum cholesterol was high in the only one in whom it was available. Only one of the five moderate lesions occurred in a female (Table 2). Thus coronary atherosclerotic occlusive lesions occurred more commonly in the Nigerian male who was hypertensive and around the fifth to seventh decade of life. Hypertension is common in Nigeria (Akinkugbe, 1971)but the generally low prevalence of coronary atherosclerosis in Nigeria confirms the suggestion that hypertension by itself is not an important predisposing factor of coronary artery disease, except in the presence of other major predisposing factors (SEEDAT & PILLAY, 1977).

Of the known major predisposing factors to coronary artery disease, the ones that appeared to have offered relative protection against coronarv arterv disease in Nigeria include: (a:, a low level of serum cholesterol (EDOZIEN. 1965: TAYLOR. 19711 and Cb) a low incidence of cigarette smokers @EMI+EARS~ ‘& ELEGBELEYE, 1973). However, recent studies (TAYLOR & AGBEDANA. 1983) from Ibadan. Nieeria.

indicate that there is a relatively higher levelof s&m cholesterol among Nigerians in the high socio-economic class than in those in the low socio-economic class. Also they found that, whereas those in the low socio-economic class manifested no significant rise of serum cholesterol with age, this rise was significant in those of the high socio-economic class. Thus in the

age group of 21 to 30 years, the serum cholesterol values were 170 f 29 (males) and 189 + 24 (females) versus 144 + 26 (males) and 165 k 28 (females) respectively in the high and low socio-economic groups. In the age group 41 to 50 years, the serum cholesterol values were 217 f 35 (males) respectively in the high and low socio-economic groups. Also a survey carried out in 1973 in the city of Lagos (FEMI-PEARSE & ELEGBELEYE, 1973), reported the prevalence rate of cigarette smokersas 9*2%, whereas a preliminary survey of about two thousand subjects at Ile-Ife, Nigeria showed the prevalence of cigarette smoking to be 16.8% (OGUNNOWO & ANDY, 1984). As the socio-economic conditions of black Africans and their life expectancy improve, more subjects are likely to acquire most of the major factors that predispose to coronary artery disease. Some urban elites appear to have already acquired most of these major factors, and, as this preliminary observation and the observations of ISAACSON (1977) from South Africa indicate, the prevalence rate and the severity of coronary thrombosis and its major complications is likely to increase proportionately. The clinical manifestations of the diseasemay lag behind the pathological changes for a while, mainly becauseof the time required between exposure and development of coronary lesions severeenough to produce symptoms and complications. Findings in this study do not support any genetic protection of the African from coronary artery disease. Physicians in Africa should be on the look-out

fooe;ky -increases in prevalence of coronary artery

CORONARY

926

ARTERY

PATHOLOGY

References

Becker, B. J. P. (1946). Cardiovascular diseasein the Bantu and Coloured races of South Africa IV. Atberomatosis. South African Journal

of Medical Sciences, 2, 97-102.

Edozien. 1. C. (1965). A biochemical evaluation of the state of nutrition h Nigeria. West Ajiican MedicalJoumul, 10, 3-21 and 23-28. Femi-Pearse & Elegbeleye, C. M. (1973). Respiratory symptoms and their relationship to cigarette smoking, dusty occupations and domestic air pollution. Studies in random samples of an urban African population. West Ajiican Medical 3ouma1, 22, 57-65. Florentin, R. A., Lee, K. T., Daoud, A. S., Devis, J. N. P., Hall. E. W. & Goodale. F. (1963). Geoeraahical pathology of atherosclerosis: A study of’the ageo
THE

ROYAL

SOCIETY

OF NIGERIANS

coronary artery disease.3oumal of Clinical Investigation, 33. 1366-1371. Isaacson, C. (1977). Changing pattern of heart disease in South African blacks. South Ajiican MedicalJournal, 52, 793-798.

Seedat, Y. K. & Pillay, N. (1977). Myocardial infarction in the African hypertensive patient. American Heart Journal, 94, 388-389.

Taylor, G. 0. (1971). Studies on serum lipids in Nigerians. Tropical and Geographical Medicine, 23, 158-166. Taylor, G. 0. & Agbedana, E. 0. (1983). A comparative study of plasma high density lipoprotein cholesterol in two groups of Nigerians of different socio-economic status. Ajican 3oumal of Medical Science, 12, 23-28. Williams, A. 0. (1971). Coronary atherosclerosisin Nigeria. British Heart 3ourna1, 33, 85-100.

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