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Characteristics of South African Bantu who have suffered from myocardial infarction∗
Characteristics
of South
Have
from Myocardial
Suffered
HARRY C. SEFTEL,
M.B.,
KEVIN J.
KEELEY,
African
Bantu
Infarction*
M.B. and ALEXANDER R.
Johannesburg,
Who
P. WALKER, PH.D.
South Africa
A
MONGmost white populations, heart disease caused by coronary atherosclerosis or thrombosis is the greatest single cause of death. In New York’ in 1955, according to death certificates, the disease (classification 420) accounted for 34 per cent of deaths. In Edinburgh2 the corresponding figure for 1956 was 30 per cent. In Johannesburg3 in 1959, for the white population the figure was 22 per cent. Among the South African Bantu, judging from necropsy studies undertaken at several urban centers, mortality from the disease is extremely 10w.~-Q At this hospital (2,200 beds), up to the present, there have been 3 to 5 cases per year from an urban population of about two thirds of a million. The favorable situation depicted has received ample confirmation from extensive electrocardiographic studies undertaken on elderly Bantu, lo also from clinical impressions on of angina pectoris in hospital the rarity practice.8s10 Although very few deaths among Bantu are caused by coronary heart disease, we regard it imperative that the characteristics of known sufferers be examined carefully. Primarily this will aid in learning whether the factors associated with high mortality from the disease among white people,11~‘2 such as elevated serum choleshypertension, overweight and terol level, diabetes, also prevail in the very few affected among the relatively underdeveloped Bantu population. The Johannesburg urban Bantu population, although largely unsophisticated, includes all strata ranging from the near primitive to the almost completely Westernized. The population, furthermore is continually changing socioeconomically, almost invariably in the direction of increasing sophistication. This dynamic state of a population in transition lends added significance to the investigation in
mind. As far as we are aware, no study of this type has been reported on similar populations. Briefly, we have sought to analyze the characteristics of our Bantu patients, living or dead, with myocardial infarction in which all evidence pointed to coronary atherosclerosis or thrombosis as the cause. Patients were examined in regard to clinical state, blood biochemistry, pathology (when possible), as well as habitual diet, alcohol intake, smoking habits, physical activity, socioeconomic state and other factors. SUBJECTS AND METHODS Thirty pure Bantu subjects,
27 men and 3 women, with proved myocardial infarction were studied. These constituted all cases discovered by an intensive search of our clinical and pathologic records for the years 1951 to 1961. This hospital serves a population of between 600,000 and 700,000 Bantu living in and around Johannesburg. In the period mentioned the annual admission rate increased from 26,000 to 48,000. Diagnosis: In 15 patients the diagnosis was proved post mortem by the detection of recent or old myocardial infarcts associated with atherosclerotic or thrombotic occlusion of the coronary arteries. In the other 15 patients, the diagnosis of infarction was made during life and was based primarily on Eleven unequivocal electrocardiographic evidence. of these patients had signs of anterior myocardial infarction-pathologic Q waves in leads I, aVL and the precordial leads, and 4 patients had signs of posterior infarction-Q waves in leads II and III and aVF. In all but 1 of the 15 cases, the Q waves were associated with elevated S-T segments, and serial electrocardiograms revealed the sequence of S-T segment and T wave changes characteristic of recent infarction.13 The single exception had striking Q waves in leads I, aVL and all the precordial leads; these changes were discovered during routine electrocardiography in a patient who had never had cardiac symptoms. In the other 14, apart from electrocardiographic evidence, there was good clinical or
* From the Baragwanath Non-European Hospital and the Human Institute for Medical Research, Johannesburg, South Africa. 148
Biochemistry
THE
Research
AMERICAN
Unit,
JOURNAL
South
African
OF CARDIOLOGY
Myocardial
Infarction
laboratory evidence of infarction. Thirteen presented with chest pain strongly suggesting myocardial infarction or angina of effort, while the fourteenth was admitted with aphasia and hemiplegia, almost certainly caused by cerebral embolism. Four patients had intermittent claudication with impalpable or diminished femoral, popliteal, tibia1 or pedal pulses. Serum transaminase (glutamic oxalacetic or glutamic pyruvic) or lactic acid dehydrogenase activity was determined in 11 cases, and in all, the level of activity of at least one of these enzymes was raised. Nine of the patients diagnosed during life were seen by us personally; 4 others were examined by colleagues at this hospital. In none of the 15 cases was there any evidence to suggest that the myocardial infarction was due to causes other than coronary atherosclerosis or thrombosis. In particular, no patient showed signs, clinical or serologic, of syphilis. Clinicopatholo,yic Investicqation: All 30 cases were analyzed in respect to a number of clinical, biochemical, pathologic and personal characteristics. The clinical information was based on our own observations in 11 cases and was extracted from hospital records in the remaining 19. Data on the levels of one or more blood lipid fractions were available in In all patients the diagnosis of myocardial 14 cases. infarction had been made or suspected during life, and certain blood lipid components were determined as routine investigational procedures. For the blood lipid component data we are indebted to Dr. I. Bersohn, Head of the Ernest-Oppenheimer Research Unit for Cardiovascular Disease. The pathologfc information on the 15 deceased patients was based on the records of routine postmortem examinations performed at this hospital by pathologists of the South African Institute for Medical Research. In the investigation of personal characteristics such as diet and socioeconomic status, we were aided by trained Bantu social workers who interviewed the patients or their relatives in their homes. They were able to trace the present or past addresses of 26 of the 30 patients and to obtain reliable information in 20. Information was regarded as reliable only if obtained from the patients themselves (11 cases), or, in case of death, from their wives (5 cases) or their adult offIn most instances the information spring (4 cases). Nine of the 20 was checked at a second interview. patients were interviewed independently by ourselves, and our findings agreed well with those of the social workers. In the case of 1 patient, relatives could not be traced, but his background was sufficiently well documented since he had been a long term prisoner (on account of habitual violence) who suffered his myocardial infarction during the seventeenth year of his sentence. The patients pared
with myocardial
with controls,
will be described to men
since
infarction. AUGUST
1963
later.
they
infarction
the manner
of whose
Comparisons
comprised
were comselection
were confined
27 of the 30 cases
of
in Bantu
149 RESULTS
Table
I summarizes
CLINICrlL Sex
INFORMATION
and Age at Time of Diagnosis:
predominance can
of men,
be explained
higher
most of the findings.
only
admission The
wards.
out
partly
rate
great
27 for
The of
30
striking patients,
by the 20 per cent men
majority
to our of
medical
patients
(24)
65 years of age when myocardial infarction was first diagnosed, but 3 were aged 31, 35 and 37 years, respectiv-ely. All 3 women were postmenopausal. Perzod qf Diagnosis: Eighteen of the 30 patients were diagnosed during the four-year period, 1958 to 1961 (total admissions being 185,000), as compared with 12 in the previous seven-year period, 1951 to 1957 (total admissions, 232,000). This suggests that myocardial infarction in the Bantu, although rare, may- be increasing. Blood Pressure: Nine (33’%) of the 27 men having with infarction were hypertensive, diastolic pressures varying between 100 and 150 mm. Hg. This proportion probably is an underestimate, since most of the blood pressure readings were recorded during the acute stage of myocardial infarction when the pressure tends to fall. Nevertheless, the proportion is significantly greater than the figure of 14 per cent, which we have found in the general Johannesburg male Bantu population of similar age. One of the 3 women was hypertensive. Diabetes Mel&us: Urine was examined for reducing substances in 25 of the men; 3 (12y0) had glycosuria, subsequent blood tests revealing the patients to be diabetic. This proportion exceeds by 20 times the incidence of diabetes found in 756 male Bantu of similar age attending our Casualty Department.‘* A fourth man had glycosuria, but his blood sugar was not estimated. One of the 3 women with infarction was diabetic. This feature was arbitrarily- asConstitutiorl: sessed as obese, average or thin and was known in 24 of the men. Eight (33yc) were obese, whereas of 100 controls drawn from the Casualty Department, only 12 per cent were obese. were
between
PERSONAL
40
and
CHARACTERISTICS
Nineteen of the 21 patients for information was considered reliable and each was matched for age with drawn at random from the hospital’s register.
whom this were men, 5 controls admission
Seftel,
150
Keeley
and Walker
TABLE I Characteristics
-p
p---Clinical No., Sex
of 30 Bantu Cases of Myocardial
Data---
.7Diastolic B.P.
Age
Build
(mm.
Hg)
Standard of Educadon
Diabetes
1M
31
Fat
90
2M
47
Fat
80
+
3M
59
Fat
15
?*
I
Occupation
Infarction
-Personal DaraWage per MO. (a
Commercial traveler School principal School principal
is:. 10
Physical Activity
Diet
5?.
Light
Western
105
Light
Western
50
Light
Western
B. 4M
53
Thin
80
5M
50
Thin
80
6M 7h4 EM
45 42 48
Fat Medium Fat
90 RO 90
9M
62
Thin
115
10M 11M 12M
52 46 48
Medium Medium Medium
140 140 70
_
8 4 2 3 2 6 4 Nil Nil
r _ 5 _ -
23 20 25 16 15 9 10 11 15
Priest Cook Constable Laborer Cook Baker Cook Cook Laborer
Light Light Mod. Mod. Light Light Light Light Mod.
Intermediate Intermediate Intermediate Intermediate Intermediate Intermediate Intermediate Intermediate Intermediate
c. 13F 14M 15M 16M 17M 18F 19M 20M 21M
58 70 60 52 48 62 64 45 75
Fat Thin Thin Fat Medium Medium Fat Medium Medium
22M 23F 24M 25M
64 61 56 40
Medium Fat Medium
80 100 80
+ _ _
85 80 100
_
100 100 90
_ -
85 60 100 85
_ _ _
27M 26M
35 52
Medium
150 70
II
28M 29M 30M
42 45 37
Medium
120 75 85
_ _ _
t Means and standard Mod. = moderate.
Thin
deviations
for normal
urban
Bantu.l6-1*
Nil 2 Nil 3
Housewife Laborer Watchman Watchman Prisoner Housewife Laborer Laborer Laborer
Nii 1 Nil 4
Mod. Mod. Light Light Heavy Mod. Mod. Heavy Mod.
14 17
‘is 11
Q Carrr
Q Cores
Ban&l Bantu Bantu Bantu Bantu Bantu Bantu Bantll Bantu
I i
1::
:.:
..:
* Glycosuria
Tribe and Birthplace: Most tribal groups were represented, and the distribution of the patients was similar to that of the controls. Birthplace largely was in keeping with tribal distribution. Period of Urbanization: All 19 male patients had lived in a city for periods varying between 11 and 60 years before their infarction was first On the average, two thirds of their diagnosed. lives before diagnosis had been spent in a city. Figures for the controls were similar.
present
but
blood
suqnr
not estimated,
Cholest.
=
cholesterol
Educational Status: This was known in all but 1 of the 19 male patients and varied considerHowever, 4 (22%) had reached standard ably. 8 or higher (standard 10 being that of matriculants), whereas only 4 per cent of the controls had reached this level. If the attainment of standard 5 or more be used as the criterion, the difference between the patients with infarction (27yc) and the controls (21%) is not impressive. Occupation: Although a number of patients THE
AMERICAN
JOURNAL
OF
CARDIOLOGY
Myocardial
Infarction TABLE
--Total (mg. “;)
t6OO i
Phospholipid cmg.?)
110 220 zt 38
934
Cholest. (mg.%I
150 i
Cholest./ Phospho.
33 0.70 f
0.09
TOtZ,l Fatty Acids (mg. 0”)
500 zk 80
151
I (continued)
Lipids-------
--Blood
in Bantu
-----
_ ------~Lipoproteins----7 Triglycerides img. %c)
75 f
20
370
t
S,
40 zt 9
60 i
12
a Cholest.
B Cholest.
(mg. %I
(mg. %)
31 f7
69f14
20
X0
22
78
X32
246
208
0.85
536
264
23
77
10
90
804
271
202
0.90
4.51
140
28
72
13
a7
815 518 710 590 835
264 182 200 202 294
254 160 189 180 2-‘4
0 96 0 88 0.95 0.89 0 93
473 287 508 342 482
165 98 250 113 ._.
30 5 17.5 21.8 19
69.5 82.5 78.2 81
12 22 17 14 13
88 78 83 86 87
c-Coronary Athcroma
Pathology---Thrombus
Mod.
Recent
SeWJre
Old
kid Mild Mild Mild Mild Mild
Recent ReCtXlt R‘XSlt Recent ReWlt Old
on II Hantu Diet
391 454 540 451
158 219 212 211
?9 156 192 148
0.50 0.71 0.91 0.71
257 212 276
135
.::
38 31
6;
G.5 17
69
“’ 60.5 83
.
... ... ... ...
... ... ... ...
... ... ... ...
... ... ... ...
... ... ... ...
...
Severe
... ...
SWCTC SWCX Mod.
655
226
208 “’ 190
0.92 “.
370
116 ‘.’
Old Suhintimal
Mod.
had been employed in more than one occupation, in most instances one particular type of work predominated, and this was used as the basis of classification. Twenty-one per cent of the men with infarction were skilled (school principal, priest, commercial traveler), 32 per cent semiskilled (cook, baker, police constable) and 47 per cent unskilled (manual laborer, watchman). Among the controls there were fewer (10%) in the skilled and more (64%) in AUGUST 1963
1’;
83’
1’0
90
the unskilled groups, the proportions of semiskilled in the two groups being similar. Five of the 19 men (26$!&) were employed as cooks in homes or institutions of white South i\fricans or in a bakery, whereas only 2 per cent of the controls were so employed. Monthly Wage: Apart from those of the school principals and commercial traveler, the monthly earnings fell within the range of g9 to s25. The mean for the whole group of men
152
Seftel,
Keeley
with infarction was g23; but if the far higher salary of one of the school principals is excluded, the mean is Zl8. This is little more than the mean of Zl4 earned by the controls. Physical Activity: This was assessed by inquiring about the degree of physical exertion associated with the subject’s occupation, hobbies and sporting activities and was arbitrarily classified as light, moderate or heavy. It was light in 58 per cent, moderate in 32 per cent, and heavy in 10 per cent of the male cases of infarction. Among the controls it was light in only 27 per cent, moderate in 30 per cent, and heavy in 43 per cent. Diet: Subjects or their relatives were asked to describe an average day’s diet, giving the number of meals eaten and foodstuffs consumed. Particular attention was paid to the amount and frequency that animal protein and fatty foods were eaten. Subjects were also asked whether their recent diets differed in any way from those in the past and, if so, in what respects. From this information we were able to obtain a reasonable idea of the patients’ habitual diets prior to seeking medical attention. The subjects were divided into three dietary categories: (A) Western. Three men with infarction (16%) enjoyed a diet high in animal protein and fat, essentially similar to that of the average local white population. Only 3 per cent of the controls lived on this Western diet. (B) Bank Seven (37oj,) men with infarction consumed a diet high in carbohydrate, i.e., mostly maize meal, bread sugar and potatoes, and relatively low in animal protein and fatty foods. Meat was eaten three to seven times a week; milk was consumed in small quantities, usually with tea, coffee or porridge; and other dairy products such as butter, cheese, and also eggs were seldom eaten or not at all. Peanut butter or margarine were sometimes eaten. Eighty-four per cent of the controls lived on this type of diet, which is characteristical of almost all rural Bantu.15 (C) Intermediate. In 9 men (47%) with infarction, the diet was intermediate between Western and Bantu. Thus, although carbohydrate was still the major constituent, meat or fish was eaten at least once, and often, twice a day; butter, cheese or eggs were also eaten daily. Two subjects drank one pint of milk 1 was particularly fond of beef fat, 1 of a day; pork, and another of chocolate. Only 13 per cent of the controls consumed an intermediate diet. Alcohol and Tobacco Consumption: Characteris-
and Walker tics of patients in this regard were the same as those of the control group. Family History of Myocardial Infarction: Replies on this point were all negative, both in patients with infarction and in the controls, but their reliability is uncertain. BLOOD
LIPIDS
In 14 of the 30 cases a number of blood lipid fractions had been determined. The data, together with the mean and standard deviation values for normal urban South African Bantu,16-19 are listed in Table I. Most of the determinations were performed between one and four weeks after the episode of infarction while patients were receiving coumarin-type anticoagulants, only 1 patient being on heparin. The results show that in 11 cases, the level of at least one of the lipid fractions was elevated; in 9, three or more fractions were raised. PATHOLOGY
Of the 15 patients examined post mortem, the myocardial infarcts were old in 7, including 2 with aneurysms, recent in 6, and both old and recent in 2. All infarcts were left ventricular, being predominantly apical in 6, anterior in 3, posterior in 5 and septal in 1. In all but 1, the infarct was the direct cause of death, i.e., congestive cardiac or left ventricular failure, aror the indirect cause, rhythmia or shock, The excepcerebral or pulmonary embolism. tion died of pyococcal meningitis, and at necropsy an old aneurysmal infarct was found. All 15 cases showed occlusion of at least one Six had severe, of the major coronary arteries. extensive atherosclerosis resulting in complete or nearly complete obstruction of the right, left or left anterior descending coronary arteries. In 2 of these patients the atheroma was complicated and in 2 others, by old by calcification, thrombus. In 3 cases coronary atherosclerosis was In 2 of these, occlusion resulted moderate. from a superimposed recent thrombus, while in the third it was caused by hemorrhage into an atheromatous plaque. In the remaining 6 cases, the occlusive lesion consisted largely of thrombus, recent in 5 and old in 1. In all 6 the thrombus was superimposed on a small, localized, atheromatous plaque which in no case encroached upon more In all 6 patients, than one third of the lumen. the rest of the coronary arterial tree was either normal or showed atheroma which was deTHE AMERICAN
JOURNAL
OF
CARDIOLOGY
Myocardial
Infarction
In all patients the the left anterior descending
scribed as mild or minimal. occlusion coronary
involved artery.
CORRELATION
BY
DIET
When the 21 patients, for whom reliable information personal was available, were grouped into (a) those enjoying a Western or intermediate type of diet and (b) those consuming a Bantu diet, the following correlations emerged (Table I). The 12 patients in group A had a relatively high educational, occupational and economic status and were largely sedentary workers. Blood lipids were examined in 8, and in all these patients the levels of at least three of the fractions were raised. Three patients definitely, and a further patient possibly, were diabetic. Of the 4 who came to necropsy, 3 showed severe coronary atherosclerosis; in 2 this was the sole, and in the third, the major cause of coronary occlusion. In the fourth case, atheroma and thrombosis appeared to contribute equally to the occlusion, One of the 4 suffered also from gangrene due to severe femoral atherosclerosis. Four other patients in this group had intermittent claudication with absent or diminished femoral, popliteal, tibia1 or pedal pulses, and in 1 of these patients, calcified atherosclerotic plaques had been demonstrated radiologically along the popliteal artery. The 9 subjects on the Bantu diet were of low socioeconomic status and were relatively active physically. The blood lipids in 4 cases tended to be low or normal, with occasionally a raised value. In all of 6 patients examined post mortem, the lesion causing the coronary occlusion consisted largely of thrombus superimposed on a small plaque of atheroma along the course of the left anterior descending artery, IhSCUSSION
A partly retrospective study based on a relatively small number of patients, some of whom are incompletely documented, has obvious limitations. There are a number of trends, nevertheless, which appear to be significant, and whose bearing on the problem of coronary heart disease in white populations merits consideration. It is widely believed that Western modes of living, particularly when associated with certain conditions common among Western communities, such as diabetes mellitus, hypertension AUGUST
1963
in Bantu
153
and obesity, are important factors in the pathogenesis of the modern epidemic of ischemic heart disease. This view receives much support from the present study. In comparison with control groups, the Bantu patients with infarction showed a higher incidence of hypertension, diabetes and obesity, were more advanced socioeconomically, were less active physically, and more often were habituated to a diet higher in animal protein and fat. There was a marked preponderance of men, who in general have greater opportunities to become sophisticated. In the majority of patients whose blood lipids were determined, the levels were higher than average values in urban Bantu. In addition, some evidence was forthcoming that the frequency of coronary heart disease atnong the Johannesburg Bantu is rising, this occurring simultaneously with a period remarkable for the acceleration of Westernization of these people. All these findings, therefore, are in accord with the marked increase in the prevalence of ischemic heart disease which has followed the Westernization of other such peoples previously habituated to relatively primitive diets, like the Japanese settlers in Hawaii and California,20 Yemenites in Israekz’ and Indians in Central and Southern Africa.22a23 Allowing that Westernization is associated with an increase in coronary heart disease, the important question, as yet unanswered, is which of the variety of concomitant changes bears chief responsibility. White populations are characterized by consumption of a diet rich in animal fat and protein, lack of physical exercise, advanced socioeconomic status with its emotional stress deriving from heavy occupational responsibilities and increasingly- complex modes of living. Each of these factors has its protagonists; yet, despite intensive study, no unanimity has been reached on their relative significance. In large measure, controversy stems from the fact that all these features tend to occur simultaneously, so that the influence and specific responsibility of each adverse component is not easily assessed. The present study is similarly limited, but two factors, a diet rrlatively high in animal fat and a sedentary manner of life, appear to be more important than advanced socioeconomic status. This is demonstrated by the high proportion of cooks in the series, who by virtue of their occupation were sedentary and had ready access to a Western type of diet but whose socioeconomic status was relatively low. This situation is consistent with the oft repeated
Seftel,
Keeley
war-time experience of several European countries (Scandinavia,*4 Holland,25 Germany26) in which the converse occurred; during the period of food privation, a concomitant decrease in severity of atheroma and deaths from coronary heart disease was reported. In addition, the situation is in harmony with observations on long term white prisoners at Pretoria Gaol, where the diet, inter alia, is low in fat and where, for several decades, deaths from coronary heart disease have been remarkably infrequent.27 As to the factors of hypertension, diabetes me&us and obesity, all were found to be significantly associated with the Bantu cases of infarction. In white populations it is commonly held that each may accelerate the development of atherosclerosis, but none is regarded as primary, if only because atherosclerosis usually develops in their absence. Furthermore, all three factors occur in a proportion of the general urban Bantu population among whom the more severe grades of atherosclerosis are uncommon. These considerations suggest not only that hypertension, diabetes and obesity may be limited to the secondary role of aggravational factors in atherogenesis, but that even then their deleterious influence is conditional to a Western type of environment.28 Such is the case in white communities in general, and in our Bantu cases of infarction in particular. Tile pattern of coronary occlusive lesions in the 15 cases examined post mortem is of considerable interest. Although atherosclerosis was found in all, in only 6 was it the main factor causing occlusion. In 3 it was moderate, and thrombosis or subintimal hemorrhage appeared to be equally important. In the remaining 6, it was mild and the occlusion consisted largely of thrombus. In these cases, the thrombus was superimposed on a small plaque of atheroma, but the latter is unlikely to have caused the thrombus. Such mild atheroma must be extremely common in both white and Bantu subjects, and it may be speculated that increased coagulability or decreased fibrinolytic activity of the blood was mainly responsible. It would a.ppear, then, that the majority of fatal coronary occlusions in the Bantu are divisible into two groups: one caused mainly by atherosclerosis and the other, mainly by thrombosis. This pattern diff‘ers considerably from that found in white populations. Thus, in recent studies both in Britain*9 and the United States,30 it was demonstrated unequivocaliy that the crucial lesion
and Walker in white subjects dying from ischemic heart disease is severe atheroscierosis; thrombosis was never observed in the absence of advanced atherosclerosis. Some workers31-34 have considered or implied that the current increase in mortality and morbidity from coronary heart disease in white populations is related to a rising incidence of coronary thrombosis, rather than to atherosclerosis, which it is thought may even be decreasing; 31 but in neither of the former cited studies2g,30 was there evidence to support this view. Correlation of Anatomic Lesions with Diet: That the Bantu pattern of lesions is not fortuitous is suggested by the correlations which emerge when the cases of infarction are classified according to diet. Those enjoying a Western type of diet were advanced socioeconomically, were largely sedentary and showed relatively high blood lipid levels; the occlusion of their coronary vessels appeared to be largely atherosclerotic. In those patients on the Bantu diet, the opposite obtained in respect of socioeconomic physical activity and blood lipids; status, their lesions were mainly thrombotic. The number of cases is small and the number esamined at necropsy smaller still, but the trend seems definite. It would, therefore, appear as stated that coronary occlusion in the Bantu is not a homogeneous condition but includes at least two moieties. The first clearly involves Bantu who have been, or are in the process of being Westernized, and almost certainly they are affected by the occlusive atherosclerosis as seen in white populations. This suggests that Westernization increases the prevalence of coronary occlusion primarily by promoting atherogenesis. In passing, it should be indicated that we are somewhat puzzled by the infrequency of infarction among these people. There is a by no means insignificant proportion of Johannesburg Bantu who have high serum cholesterol levels, long blood clot lysis times, occupations; hypertension, obesity, sedentary )-et cases of infarction remain rare.“j The primitive second moiety, involving relatively Bantu, is mysterious, and we have no explanation to offer for the occurrence of their predominantly thrombotic lesions. In fact, the characteristics of these Bantu generally are such as are currently believed to militate against thrombosis. The sufferers in this second group have little or no counterpart among white subjects, among whom coronary thrombosis rarely occurs in the absence of advanced atherosclerosis. THE AMERICAN
JOURNAL
OF
CARDIOLOGY
Myocardial
Infarction
SUMMARY
Thirty cases of myocardial infarction in Bantu subjects were analyzed in respect to a number of clinical, personal, biochemical and pathologic characteristics. The findings varied considerably, but in comparison with control groups, the Bantu cases of infarction showed a marked predominance of males, had a higher incidence of hypertension, diabetes and obesity, a higher educational, ocand economic status, cupational were less active physically, and were more often habituated to a diet relatively high in animal protein and fat. In the majorit)- of cases in which blood lipid components were determined, levels were found to be elevated. Fifteen of the 30 patients were examined In 6 cases the lesion occluding the post mortrm. coronary arteries was largely atherosclerotic, with or without superimposed thrombosis. In another 6, coronary atherosclerosis was mild, and the occlusive lesion consisted mainly of In 3 cases the occlusion was due to thrombus. a combination of moderate atheroma with thrombosis or subintimal hemorrhage. When the Bantu cases of infarction were classified according IO the type of diet consumed, Those the following correlation emerged. living on a diet high in animal protein and fat relatively advanced socioeconomically, were were largely sedentary and had high blood lipid levels; and, in cases coming to necropsy, the coronary occlusion was due mainly to atheroSubjects on a diet low in animal prosclerosis. tein and Sat were of low socioeconomic status, were relatively active physically and had low or normal blood lipid levels (for Bantu); and at necropsy the occlusive lesion was predominantly thrombotic. The bearing of these findings on the problem of ischemic heart disease in white populations is discussed.
2. City and Report 1956.
REFERENCES 1. Summary of Vital Statistics. Department The (:ity of New York, 1956.
AUGUST
1963
of Edinburgh: Annual Health Dcpartmrnt for
Register of Draths: Department nesburg Municipaiity, 1959.
4.
RECKER. B. .J. P. Cardio-vascular discase in the Bantu and coloured races of South .4frica. IV. Athcromwtosis. South iffrican J. M. SC.. 11
of Health,
Johan-
Athcrosclcrosis
and its cerebral complications in thr South .Ifrican Bantu. Lnnwt, 1 : 231, 1958. Aortic and coronary 7. SAWS> M. I. Cirin the thrw racial groups in Cape Town. c,ilu/ion, 22 : 06. 1960. Atheroma in thr African (Bantu) 8. \YAIN!\RIGH?.. .r. in Natal. I,ant.r(, 1 : 366, 1961. 9. REW, H. and IS.UCSON, C. in the Bantu: thr distribution of athrromatous lesions Circulation, 25: in Africans over 50 years of age. 66. 1962. 10. SEFTEI,. H. C.. KEEI.EY. K. .I., WALKER. A. K. P.. THERON. J. .I. and DE LANGE, D. J. Unpublished work ( 1962 ). 11. DR.WB. R. M.. BUECHLEY, R. W. and BRESLOW, L. \‘. An rpidemiological investigation of coronary heart disrasr in the Califorma Health Survey P opulation. Am. J. Pub. Health. 47: 43 (Suppl.), 1957. 12. DAWBER. T. R.. KANNEL, W. B., Rwors~~s, N. and KAGAN, A. The epidemiology of coronary heart disease-The Framingham enquiry. Proc. Roy.
Sm. .k’~d., 55: 265, 1962. 13. Hypertension and Coronary Hmlth Or,qanization Tech. p. 25. World Health
Heart
Rep.
ltrorld
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168, 1959.
Ccncva. Diabetes in the SEF.~EI., H. C. and ABRAMS, G. J. Bantu. &it. M. J., 1 : 1207, 1960. 15. \YALKER. A. R. P. Certain biochemical findings A1211.:v
s-.. 69: 989, 1958. 16. ANTONIS. A. and BERSO~XN, I.
17.
18.
19. 20.
21.
22. of Health,
Royal Borough of the Public
1.55
3.
ACKNOWLEDGMENT 1%‘e are grateful to the Superintendent of this hospital, Dr. I. Frack, and to our fellow physicians and pathologists for permission to use the case reports of the patients Much of the eliciting of information on the concerned. patients’ antecedents was carried out by Bantu social workers, Mr. John Ketlele and Mr. Igantius Tsoku. Considcrablv assistance in collating observations was given by medical student Marie Andre. The expenses of the investigation were met in part by a grant (H-4244) from the National Heart Institute, c’. S. Public Health Service.
in Bantu
Annual Report of the South African Institute for Medical Research. Johannesburg, p. 11. 1959. ANYONIS. A. and BERSOHN. I. Serum t+lyceride lrvels in South African Europeans and Bantu, and in ischaemic heart disease. Lancet, 1 : 998: 1960. The influence of diet :\NI.ONIS, A. and BERSOHN, I. on strum lipids in South African Bantu and white prisoners. ilm. J. Clin. Nutrition. 10: 484. 1962. J\NTONIS.A. and BERSOHN, I. Personal communication. KEYS, A. Field studies in 1955. In: Cardiovascular Epidemiology, p. 175. New York. 1956. Hoeber-Harper. TOOR. M., KATsCHALSKY, A., Ac~oa. .I. and ;ZI.LALOUF, D. .4therosclerosis and related factors in immigrants to Israel. Circulation, 22 : 265. 1960. CIIARTERS, A. D. and ARYA, B. P. Incidence of ischarmic heart disease among Indians in Krnya. Imwt, 1 : 288, 1960.
Seftel, 23.
WALKER,
disease 1961. 24.
25.
26.
27.
28.
A.
in
Keeley
R. P. Mortality from coronary heart Indian populations. Lmc~t, 1 : 512,
G. 6Var time lessons on arteriosclerotic heart disease from northern Europe. In: Ref. 20. p. 8. SCHORNAOEL. H. B. The connection between nutrition and mortality from coronary sclerosis during and after World War II. Down. med. Gag. et trap., 5: 173, 1953. Nutrition Abstr. 3 Rev., 24: 193, 1954. P~zor.o, F. A. In: Atherosclerosis and Nutrition, p. 246. Darmstadt, 1959. Verlag Dr. Dietrich Steinkopff. Reviewed in ilm. J. Clin. Nutrition, 8: 384, 1960. WALKER, A. R. P. et al. Coronary heart disease in South African “poor whites” and white prisoners habituated to a Bantu type of diet. Am. .J. Clin. Nutrition, 9: 643, 1961. WALKER, A. R. P. Fat, calcium and coronary disease. hit. M. J., 1 : 1660, 1960. RIORCK:
and Walker 29. CRAWFORD, T., DEXTER, D. and TEARE, R. D. Coronary artery pathology in sudden death from myocardial ischaemia. Lancet, 1: 181, 1961. 30. SPAIN, D. M. and BRADESS, V. A. The relationship of coronary thrombosis to coronary atherosclerosis and ischaemic heart disease (a necropsy study covering a period of 25 yrars). Am. J. Al. SC., 240: 701, 1960. 31. MORRIS, .J. N. Recent history of coronary disease. Lancet 1: 1, 69, 1951. 32. MORRIS, .I. N. and CRAWFORD, M. D. Coronary heart disease and physical activity of work. Rrit. M. J., 2: 1485, 1958. 33. ROBERTSON, W. B. Atherosclerosis and ischaemic heart disease: observations in Jamaica. Lancet, 1: 444, 1959. 34. ACHESON, R. M. Atherosclerosis and coronary heart disease. Law, 2: 706, 1960. 35. WALKER, A. R. P. Anomalies in the prediction of nutritional disease. Nutrition Rev., 19: 257, 1961.
THE AMERICANJOURNAL OF CARDIOLOGY
of South
Have
from Myocardial
Suffered
HARRY C. SEFTEL,
M.B.,
KEVIN J.
KEELEY,
African
Bantu
Infarction*
M.B. and ALEXANDER R.
Johannesburg,
Who
P. WALKER, PH.D.
South Africa
A
MONGmost white populations, heart disease caused by coronary atherosclerosis or thrombosis is the greatest single cause of death. In New York’ in 1955, according to death certificates, the disease (classification 420) accounted for 34 per cent of deaths. In Edinburgh2 the corresponding figure for 1956 was 30 per cent. In Johannesburg3 in 1959, for the white population the figure was 22 per cent. Among the South African Bantu, judging from necropsy studies undertaken at several urban centers, mortality from the disease is extremely 10w.~-Q At this hospital (2,200 beds), up to the present, there have been 3 to 5 cases per year from an urban population of about two thirds of a million. The favorable situation depicted has received ample confirmation from extensive electrocardiographic studies undertaken on elderly Bantu, lo also from clinical impressions on of angina pectoris in hospital the rarity practice.8s10 Although very few deaths among Bantu are caused by coronary heart disease, we regard it imperative that the characteristics of known sufferers be examined carefully. Primarily this will aid in learning whether the factors associated with high mortality from the disease among white people,11~‘2 such as elevated serum choleshypertension, overweight and terol level, diabetes, also prevail in the very few affected among the relatively underdeveloped Bantu population. The Johannesburg urban Bantu population, although largely unsophisticated, includes all strata ranging from the near primitive to the almost completely Westernized. The population, furthermore is continually changing socioeconomically, almost invariably in the direction of increasing sophistication. This dynamic state of a population in transition lends added significance to the investigation in
mind. As far as we are aware, no study of this type has been reported on similar populations. Briefly, we have sought to analyze the characteristics of our Bantu patients, living or dead, with myocardial infarction in which all evidence pointed to coronary atherosclerosis or thrombosis as the cause. Patients were examined in regard to clinical state, blood biochemistry, pathology (when possible), as well as habitual diet, alcohol intake, smoking habits, physical activity, socioeconomic state and other factors. SUBJECTS AND METHODS Thirty pure Bantu subjects,
27 men and 3 women, with proved myocardial infarction were studied. These constituted all cases discovered by an intensive search of our clinical and pathologic records for the years 1951 to 1961. This hospital serves a population of between 600,000 and 700,000 Bantu living in and around Johannesburg. In the period mentioned the annual admission rate increased from 26,000 to 48,000. Diagnosis: In 15 patients the diagnosis was proved post mortem by the detection of recent or old myocardial infarcts associated with atherosclerotic or thrombotic occlusion of the coronary arteries. In the other 15 patients, the diagnosis of infarction was made during life and was based primarily on Eleven unequivocal electrocardiographic evidence. of these patients had signs of anterior myocardial infarction-pathologic Q waves in leads I, aVL and the precordial leads, and 4 patients had signs of posterior infarction-Q waves in leads II and III and aVF. In all but 1 of the 15 cases, the Q waves were associated with elevated S-T segments, and serial electrocardiograms revealed the sequence of S-T segment and T wave changes characteristic of recent infarction.13 The single exception had striking Q waves in leads I, aVL and all the precordial leads; these changes were discovered during routine electrocardiography in a patient who had never had cardiac symptoms. In the other 14, apart from electrocardiographic evidence, there was good clinical or
* From the Baragwanath Non-European Hospital and the Human Institute for Medical Research, Johannesburg, South Africa. 148
Biochemistry
THE
Research
AMERICAN
Unit,
JOURNAL
South
African
OF CARDIOLOGY
Myocardial
Infarction
laboratory evidence of infarction. Thirteen presented with chest pain strongly suggesting myocardial infarction or angina of effort, while the fourteenth was admitted with aphasia and hemiplegia, almost certainly caused by cerebral embolism. Four patients had intermittent claudication with impalpable or diminished femoral, popliteal, tibia1 or pedal pulses. Serum transaminase (glutamic oxalacetic or glutamic pyruvic) or lactic acid dehydrogenase activity was determined in 11 cases, and in all, the level of activity of at least one of these enzymes was raised. Nine of the patients diagnosed during life were seen by us personally; 4 others were examined by colleagues at this hospital. In none of the 15 cases was there any evidence to suggest that the myocardial infarction was due to causes other than coronary atherosclerosis or thrombosis. In particular, no patient showed signs, clinical or serologic, of syphilis. Clinicopatholo,yic Investicqation: All 30 cases were analyzed in respect to a number of clinical, biochemical, pathologic and personal characteristics. The clinical information was based on our own observations in 11 cases and was extracted from hospital records in the remaining 19. Data on the levels of one or more blood lipid fractions were available in In all patients the diagnosis of myocardial 14 cases. infarction had been made or suspected during life, and certain blood lipid components were determined as routine investigational procedures. For the blood lipid component data we are indebted to Dr. I. Bersohn, Head of the Ernest-Oppenheimer Research Unit for Cardiovascular Disease. The pathologfc information on the 15 deceased patients was based on the records of routine postmortem examinations performed at this hospital by pathologists of the South African Institute for Medical Research. In the investigation of personal characteristics such as diet and socioeconomic status, we were aided by trained Bantu social workers who interviewed the patients or their relatives in their homes. They were able to trace the present or past addresses of 26 of the 30 patients and to obtain reliable information in 20. Information was regarded as reliable only if obtained from the patients themselves (11 cases), or, in case of death, from their wives (5 cases) or their adult offIn most instances the information spring (4 cases). Nine of the 20 was checked at a second interview. patients were interviewed independently by ourselves, and our findings agreed well with those of the social workers. In the case of 1 patient, relatives could not be traced, but his background was sufficiently well documented since he had been a long term prisoner (on account of habitual violence) who suffered his myocardial infarction during the seventeenth year of his sentence. The patients pared
with myocardial
with controls,
will be described to men
since
infarction. AUGUST
1963
later.
they
infarction
the manner
of whose
Comparisons
comprised
were comselection
were confined
27 of the 30 cases
of
in Bantu
149 RESULTS
Table
I summarizes
CLINICrlL Sex
INFORMATION
and Age at Time of Diagnosis:
predominance can
of men,
be explained
higher
most of the findings.
only
admission The
wards.
out
partly
rate
great
27 for
The of
30
striking patients,
by the 20 per cent men
majority
to our of
medical
patients
(24)
65 years of age when myocardial infarction was first diagnosed, but 3 were aged 31, 35 and 37 years, respectiv-ely. All 3 women were postmenopausal. Perzod qf Diagnosis: Eighteen of the 30 patients were diagnosed during the four-year period, 1958 to 1961 (total admissions being 185,000), as compared with 12 in the previous seven-year period, 1951 to 1957 (total admissions, 232,000). This suggests that myocardial infarction in the Bantu, although rare, may- be increasing. Blood Pressure: Nine (33’%) of the 27 men having with infarction were hypertensive, diastolic pressures varying between 100 and 150 mm. Hg. This proportion probably is an underestimate, since most of the blood pressure readings were recorded during the acute stage of myocardial infarction when the pressure tends to fall. Nevertheless, the proportion is significantly greater than the figure of 14 per cent, which we have found in the general Johannesburg male Bantu population of similar age. One of the 3 women was hypertensive. Diabetes Mel&us: Urine was examined for reducing substances in 25 of the men; 3 (12y0) had glycosuria, subsequent blood tests revealing the patients to be diabetic. This proportion exceeds by 20 times the incidence of diabetes found in 756 male Bantu of similar age attending our Casualty Department.‘* A fourth man had glycosuria, but his blood sugar was not estimated. One of the 3 women with infarction was diabetic. This feature was arbitrarily- asConstitutiorl: sessed as obese, average or thin and was known in 24 of the men. Eight (33yc) were obese, whereas of 100 controls drawn from the Casualty Department, only 12 per cent were obese. were
between
PERSONAL
40
and
CHARACTERISTICS
Nineteen of the 21 patients for information was considered reliable and each was matched for age with drawn at random from the hospital’s register.
whom this were men, 5 controls admission
Seftel,
150
Keeley
and Walker
TABLE I Characteristics
-p
p---Clinical No., Sex
of 30 Bantu Cases of Myocardial
Data---
.7Diastolic B.P.
Age
Build
(mm.
Hg)
Standard of Educadon
Diabetes
1M
31
Fat
90
2M
47
Fat
80
+
3M
59
Fat
15
?*
I
Occupation
Infarction
-Personal DaraWage per MO. (a
Commercial traveler School principal School principal
is:. 10
Physical Activity
Diet
5?.
Light
Western
105
Light
Western
50
Light
Western
B. 4M
53
Thin
80
5M
50
Thin
80
6M 7h4 EM
45 42 48
Fat Medium Fat
90 RO 90
9M
62
Thin
115
10M 11M 12M
52 46 48
Medium Medium Medium
140 140 70
_
8 4 2 3 2 6 4 Nil Nil
r _ 5 _ -
23 20 25 16 15 9 10 11 15
Priest Cook Constable Laborer Cook Baker Cook Cook Laborer
Light Light Mod. Mod. Light Light Light Light Mod.
Intermediate Intermediate Intermediate Intermediate Intermediate Intermediate Intermediate Intermediate Intermediate
c. 13F 14M 15M 16M 17M 18F 19M 20M 21M
58 70 60 52 48 62 64 45 75
Fat Thin Thin Fat Medium Medium Fat Medium Medium
22M 23F 24M 25M
64 61 56 40
Medium Fat Medium
80 100 80
+ _ _
85 80 100
_
100 100 90
_ -
85 60 100 85
_ _ _
27M 26M
35 52
Medium
150 70
II
28M 29M 30M
42 45 37
Medium
120 75 85
_ _ _
t Means and standard Mod. = moderate.
Thin
deviations
for normal
urban
Bantu.l6-1*
Nil 2 Nil 3
Housewife Laborer Watchman Watchman Prisoner Housewife Laborer Laborer Laborer
Nii 1 Nil 4
Mod. Mod. Light Light Heavy Mod. Mod. Heavy Mod.
14 17
‘is 11
Q Carrr
Q Cores
Ban&l Bantu Bantu Bantu Bantu Bantu Bantu Bantll Bantu
I i
1::
:.:
..:
* Glycosuria
Tribe and Birthplace: Most tribal groups were represented, and the distribution of the patients was similar to that of the controls. Birthplace largely was in keeping with tribal distribution. Period of Urbanization: All 19 male patients had lived in a city for periods varying between 11 and 60 years before their infarction was first On the average, two thirds of their diagnosed. lives before diagnosis had been spent in a city. Figures for the controls were similar.
present
but
blood
suqnr
not estimated,
Cholest.
=
cholesterol
Educational Status: This was known in all but 1 of the 19 male patients and varied considerHowever, 4 (22%) had reached standard ably. 8 or higher (standard 10 being that of matriculants), whereas only 4 per cent of the controls had reached this level. If the attainment of standard 5 or more be used as the criterion, the difference between the patients with infarction (27yc) and the controls (21%) is not impressive. Occupation: Although a number of patients THE
AMERICAN
JOURNAL
OF
CARDIOLOGY
Myocardial
Infarction TABLE
--Total (mg. “;)
t6OO i
Phospholipid cmg.?)
110 220 zt 38
934
Cholest. (mg.%I
150 i
Cholest./ Phospho.
33 0.70 f
0.09
TOtZ,l Fatty Acids (mg. 0”)
500 zk 80
151
I (continued)
Lipids-------
--Blood
in Bantu
-----
_ ------~Lipoproteins----7 Triglycerides img. %c)
75 f
20
370
t
S,
40 zt 9
60 i
12
a Cholest.
B Cholest.
(mg. %I
(mg. %)
31 f7
69f14
20
X0
22
78
X32
246
208
0.85
536
264
23
77
10
90
804
271
202
0.90
4.51
140
28
72
13
a7
815 518 710 590 835
264 182 200 202 294
254 160 189 180 2-‘4
0 96 0 88 0.95 0.89 0 93
473 287 508 342 482
165 98 250 113 ._.
30 5 17.5 21.8 19
69.5 82.5 78.2 81
12 22 17 14 13
88 78 83 86 87
c-Coronary Athcroma
Pathology---Thrombus
Mod.
Recent
SeWJre
Old
kid Mild Mild Mild Mild Mild
Recent ReCtXlt R‘XSlt Recent ReWlt Old
on II Hantu Diet
391 454 540 451
158 219 212 211
?9 156 192 148
0.50 0.71 0.91 0.71
257 212 276
135
.::
38 31
6;
G.5 17
69
“’ 60.5 83
.
... ... ... ...
... ... ... ...
... ... ... ...
... ... ... ...
... ... ... ...
...
Severe
... ...
SWCTC SWCX Mod.
655
226
208 “’ 190
0.92 “.
370
116 ‘.’
Old Suhintimal
Mod.
had been employed in more than one occupation, in most instances one particular type of work predominated, and this was used as the basis of classification. Twenty-one per cent of the men with infarction were skilled (school principal, priest, commercial traveler), 32 per cent semiskilled (cook, baker, police constable) and 47 per cent unskilled (manual laborer, watchman). Among the controls there were fewer (10%) in the skilled and more (64%) in AUGUST 1963
1’;
83’
1’0
90
the unskilled groups, the proportions of semiskilled in the two groups being similar. Five of the 19 men (26$!&) were employed as cooks in homes or institutions of white South i\fricans or in a bakery, whereas only 2 per cent of the controls were so employed. Monthly Wage: Apart from those of the school principals and commercial traveler, the monthly earnings fell within the range of g9 to s25. The mean for the whole group of men
152
Seftel,
Keeley
with infarction was g23; but if the far higher salary of one of the school principals is excluded, the mean is Zl8. This is little more than the mean of Zl4 earned by the controls. Physical Activity: This was assessed by inquiring about the degree of physical exertion associated with the subject’s occupation, hobbies and sporting activities and was arbitrarily classified as light, moderate or heavy. It was light in 58 per cent, moderate in 32 per cent, and heavy in 10 per cent of the male cases of infarction. Among the controls it was light in only 27 per cent, moderate in 30 per cent, and heavy in 43 per cent. Diet: Subjects or their relatives were asked to describe an average day’s diet, giving the number of meals eaten and foodstuffs consumed. Particular attention was paid to the amount and frequency that animal protein and fatty foods were eaten. Subjects were also asked whether their recent diets differed in any way from those in the past and, if so, in what respects. From this information we were able to obtain a reasonable idea of the patients’ habitual diets prior to seeking medical attention. The subjects were divided into three dietary categories: (A) Western. Three men with infarction (16%) enjoyed a diet high in animal protein and fat, essentially similar to that of the average local white population. Only 3 per cent of the controls lived on this Western diet. (B) Bank Seven (37oj,) men with infarction consumed a diet high in carbohydrate, i.e., mostly maize meal, bread sugar and potatoes, and relatively low in animal protein and fatty foods. Meat was eaten three to seven times a week; milk was consumed in small quantities, usually with tea, coffee or porridge; and other dairy products such as butter, cheese, and also eggs were seldom eaten or not at all. Peanut butter or margarine were sometimes eaten. Eighty-four per cent of the controls lived on this type of diet, which is characteristical of almost all rural Bantu.15 (C) Intermediate. In 9 men (47%) with infarction, the diet was intermediate between Western and Bantu. Thus, although carbohydrate was still the major constituent, meat or fish was eaten at least once, and often, twice a day; butter, cheese or eggs were also eaten daily. Two subjects drank one pint of milk 1 was particularly fond of beef fat, 1 of a day; pork, and another of chocolate. Only 13 per cent of the controls consumed an intermediate diet. Alcohol and Tobacco Consumption: Characteris-
and Walker tics of patients in this regard were the same as those of the control group. Family History of Myocardial Infarction: Replies on this point were all negative, both in patients with infarction and in the controls, but their reliability is uncertain. BLOOD
LIPIDS
In 14 of the 30 cases a number of blood lipid fractions had been determined. The data, together with the mean and standard deviation values for normal urban South African Bantu,16-19 are listed in Table I. Most of the determinations were performed between one and four weeks after the episode of infarction while patients were receiving coumarin-type anticoagulants, only 1 patient being on heparin. The results show that in 11 cases, the level of at least one of the lipid fractions was elevated; in 9, three or more fractions were raised. PATHOLOGY
Of the 15 patients examined post mortem, the myocardial infarcts were old in 7, including 2 with aneurysms, recent in 6, and both old and recent in 2. All infarcts were left ventricular, being predominantly apical in 6, anterior in 3, posterior in 5 and septal in 1. In all but 1, the infarct was the direct cause of death, i.e., congestive cardiac or left ventricular failure, aror the indirect cause, rhythmia or shock, The excepcerebral or pulmonary embolism. tion died of pyococcal meningitis, and at necropsy an old aneurysmal infarct was found. All 15 cases showed occlusion of at least one Six had severe, of the major coronary arteries. extensive atherosclerosis resulting in complete or nearly complete obstruction of the right, left or left anterior descending coronary arteries. In 2 of these patients the atheroma was complicated and in 2 others, by old by calcification, thrombus. In 3 cases coronary atherosclerosis was In 2 of these, occlusion resulted moderate. from a superimposed recent thrombus, while in the third it was caused by hemorrhage into an atheromatous plaque. In the remaining 6 cases, the occlusive lesion consisted largely of thrombus, recent in 5 and old in 1. In all 6 the thrombus was superimposed on a small, localized, atheromatous plaque which in no case encroached upon more In all 6 patients, than one third of the lumen. the rest of the coronary arterial tree was either normal or showed atheroma which was deTHE AMERICAN
JOURNAL
OF
CARDIOLOGY
Myocardial
Infarction
In all patients the the left anterior descending
scribed as mild or minimal. occlusion coronary
involved artery.
CORRELATION
BY
DIET
When the 21 patients, for whom reliable information personal was available, were grouped into (a) those enjoying a Western or intermediate type of diet and (b) those consuming a Bantu diet, the following correlations emerged (Table I). The 12 patients in group A had a relatively high educational, occupational and economic status and were largely sedentary workers. Blood lipids were examined in 8, and in all these patients the levels of at least three of the fractions were raised. Three patients definitely, and a further patient possibly, were diabetic. Of the 4 who came to necropsy, 3 showed severe coronary atherosclerosis; in 2 this was the sole, and in the third, the major cause of coronary occlusion. In the fourth case, atheroma and thrombosis appeared to contribute equally to the occlusion, One of the 4 suffered also from gangrene due to severe femoral atherosclerosis. Four other patients in this group had intermittent claudication with absent or diminished femoral, popliteal, tibia1 or pedal pulses, and in 1 of these patients, calcified atherosclerotic plaques had been demonstrated radiologically along the popliteal artery. The 9 subjects on the Bantu diet were of low socioeconomic status and were relatively active physically. The blood lipids in 4 cases tended to be low or normal, with occasionally a raised value. In all of 6 patients examined post mortem, the lesion causing the coronary occlusion consisted largely of thrombus superimposed on a small plaque of atheroma along the course of the left anterior descending artery, IhSCUSSION
A partly retrospective study based on a relatively small number of patients, some of whom are incompletely documented, has obvious limitations. There are a number of trends, nevertheless, which appear to be significant, and whose bearing on the problem of coronary heart disease in white populations merits consideration. It is widely believed that Western modes of living, particularly when associated with certain conditions common among Western communities, such as diabetes mellitus, hypertension AUGUST
1963
in Bantu
153
and obesity, are important factors in the pathogenesis of the modern epidemic of ischemic heart disease. This view receives much support from the present study. In comparison with control groups, the Bantu patients with infarction showed a higher incidence of hypertension, diabetes and obesity, were more advanced socioeconomically, were less active physically, and more often were habituated to a diet higher in animal protein and fat. There was a marked preponderance of men, who in general have greater opportunities to become sophisticated. In the majority of patients whose blood lipids were determined, the levels were higher than average values in urban Bantu. In addition, some evidence was forthcoming that the frequency of coronary heart disease atnong the Johannesburg Bantu is rising, this occurring simultaneously with a period remarkable for the acceleration of Westernization of these people. All these findings, therefore, are in accord with the marked increase in the prevalence of ischemic heart disease which has followed the Westernization of other such peoples previously habituated to relatively primitive diets, like the Japanese settlers in Hawaii and California,20 Yemenites in Israekz’ and Indians in Central and Southern Africa.22a23 Allowing that Westernization is associated with an increase in coronary heart disease, the important question, as yet unanswered, is which of the variety of concomitant changes bears chief responsibility. White populations are characterized by consumption of a diet rich in animal fat and protein, lack of physical exercise, advanced socioeconomic status with its emotional stress deriving from heavy occupational responsibilities and increasingly- complex modes of living. Each of these factors has its protagonists; yet, despite intensive study, no unanimity has been reached on their relative significance. In large measure, controversy stems from the fact that all these features tend to occur simultaneously, so that the influence and specific responsibility of each adverse component is not easily assessed. The present study is similarly limited, but two factors, a diet rrlatively high in animal fat and a sedentary manner of life, appear to be more important than advanced socioeconomic status. This is demonstrated by the high proportion of cooks in the series, who by virtue of their occupation were sedentary and had ready access to a Western type of diet but whose socioeconomic status was relatively low. This situation is consistent with the oft repeated
Seftel,
Keeley
war-time experience of several European countries (Scandinavia,*4 Holland,25 Germany26) in which the converse occurred; during the period of food privation, a concomitant decrease in severity of atheroma and deaths from coronary heart disease was reported. In addition, the situation is in harmony with observations on long term white prisoners at Pretoria Gaol, where the diet, inter alia, is low in fat and where, for several decades, deaths from coronary heart disease have been remarkably infrequent.27 As to the factors of hypertension, diabetes me&us and obesity, all were found to be significantly associated with the Bantu cases of infarction. In white populations it is commonly held that each may accelerate the development of atherosclerosis, but none is regarded as primary, if only because atherosclerosis usually develops in their absence. Furthermore, all three factors occur in a proportion of the general urban Bantu population among whom the more severe grades of atherosclerosis are uncommon. These considerations suggest not only that hypertension, diabetes and obesity may be limited to the secondary role of aggravational factors in atherogenesis, but that even then their deleterious influence is conditional to a Western type of environment.28 Such is the case in white communities in general, and in our Bantu cases of infarction in particular. Tile pattern of coronary occlusive lesions in the 15 cases examined post mortem is of considerable interest. Although atherosclerosis was found in all, in only 6 was it the main factor causing occlusion. In 3 it was moderate, and thrombosis or subintimal hemorrhage appeared to be equally important. In the remaining 6, it was mild and the occlusion consisted largely of thrombus. In these cases, the thrombus was superimposed on a small plaque of atheroma, but the latter is unlikely to have caused the thrombus. Such mild atheroma must be extremely common in both white and Bantu subjects, and it may be speculated that increased coagulability or decreased fibrinolytic activity of the blood was mainly responsible. It would a.ppear, then, that the majority of fatal coronary occlusions in the Bantu are divisible into two groups: one caused mainly by atherosclerosis and the other, mainly by thrombosis. This pattern diff‘ers considerably from that found in white populations. Thus, in recent studies both in Britain*9 and the United States,30 it was demonstrated unequivocaliy that the crucial lesion
and Walker in white subjects dying from ischemic heart disease is severe atheroscierosis; thrombosis was never observed in the absence of advanced atherosclerosis. Some workers31-34 have considered or implied that the current increase in mortality and morbidity from coronary heart disease in white populations is related to a rising incidence of coronary thrombosis, rather than to atherosclerosis, which it is thought may even be decreasing; 31 but in neither of the former cited studies2g,30 was there evidence to support this view. Correlation of Anatomic Lesions with Diet: That the Bantu pattern of lesions is not fortuitous is suggested by the correlations which emerge when the cases of infarction are classified according to diet. Those enjoying a Western type of diet were advanced socioeconomically, were largely sedentary and showed relatively high blood lipid levels; the occlusion of their coronary vessels appeared to be largely atherosclerotic. In those patients on the Bantu diet, the opposite obtained in respect of socioeconomic physical activity and blood lipids; status, their lesions were mainly thrombotic. The number of cases is small and the number esamined at necropsy smaller still, but the trend seems definite. It would, therefore, appear as stated that coronary occlusion in the Bantu is not a homogeneous condition but includes at least two moieties. The first clearly involves Bantu who have been, or are in the process of being Westernized, and almost certainly they are affected by the occlusive atherosclerosis as seen in white populations. This suggests that Westernization increases the prevalence of coronary occlusion primarily by promoting atherogenesis. In passing, it should be indicated that we are somewhat puzzled by the infrequency of infarction among these people. There is a by no means insignificant proportion of Johannesburg Bantu who have high serum cholesterol levels, long blood clot lysis times, occupations; hypertension, obesity, sedentary )-et cases of infarction remain rare.“j The primitive second moiety, involving relatively Bantu, is mysterious, and we have no explanation to offer for the occurrence of their predominantly thrombotic lesions. In fact, the characteristics of these Bantu generally are such as are currently believed to militate against thrombosis. The sufferers in this second group have little or no counterpart among white subjects, among whom coronary thrombosis rarely occurs in the absence of advanced atherosclerosis. THE AMERICAN
JOURNAL
OF
CARDIOLOGY
Myocardial
Infarction
SUMMARY
Thirty cases of myocardial infarction in Bantu subjects were analyzed in respect to a number of clinical, personal, biochemical and pathologic characteristics. The findings varied considerably, but in comparison with control groups, the Bantu cases of infarction showed a marked predominance of males, had a higher incidence of hypertension, diabetes and obesity, a higher educational, ocand economic status, cupational were less active physically, and were more often habituated to a diet relatively high in animal protein and fat. In the majorit)- of cases in which blood lipid components were determined, levels were found to be elevated. Fifteen of the 30 patients were examined In 6 cases the lesion occluding the post mortrm. coronary arteries was largely atherosclerotic, with or without superimposed thrombosis. In another 6, coronary atherosclerosis was mild, and the occlusive lesion consisted mainly of In 3 cases the occlusion was due to thrombus. a combination of moderate atheroma with thrombosis or subintimal hemorrhage. When the Bantu cases of infarction were classified according IO the type of diet consumed, Those the following correlation emerged. living on a diet high in animal protein and fat relatively advanced socioeconomically, were were largely sedentary and had high blood lipid levels; and, in cases coming to necropsy, the coronary occlusion was due mainly to atheroSubjects on a diet low in animal prosclerosis. tein and Sat were of low socioeconomic status, were relatively active physically and had low or normal blood lipid levels (for Bantu); and at necropsy the occlusive lesion was predominantly thrombotic. The bearing of these findings on the problem of ischemic heart disease in white populations is discussed.
2. City and Report 1956.
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ACKNOWLEDGMENT 1%‘e are grateful to the Superintendent of this hospital, Dr. I. Frack, and to our fellow physicians and pathologists for permission to use the case reports of the patients Much of the eliciting of information on the concerned. patients’ antecedents was carried out by Bantu social workers, Mr. John Ketlele and Mr. Igantius Tsoku. Considcrablv assistance in collating observations was given by medical student Marie Andre. The expenses of the investigation were met in part by a grant (H-4244) from the National Heart Institute, c’. S. Public Health Service.
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