Myocardial infarction over a five-year period—I. Prevalence, incidence and mortality experience

J Chron Dis 1973, Vol. 26, pp. 63-84. Pergamon Press. Printed in Great Britain

MYOCARDIAL INFARCTION OVER A FIVE-YEAR PERIOD-I. PREVALENCE, INCIDENCE AND MORTALITY EXPERIENCE JACK H. MEDALIE,HAROLDA. KAHN, HENRYN. NEUFELD, EGON Rrss, URI GOLDBOURT,TAMARPERLSTEINand DVORAORON Department of Family Medicine, National Heart and Lung Heart Institutes, Sheba Hadassah Medical

Tel Aviv University Medical School ; Institute, Bethesda, Maryland ; and Rarnbam Hospitals; and Organization, Jerusalem

(Received 28 February 1972; in final form 14 August 1972)

INTRODUCTION

THE ISCHEMICHeart Disease Project was designed as a prospective study of male adult government and municipal employees in Israel [l]. The first survey examination was performed in 1963 [2] and was followed by the second and third check-ups in 1965 [3 Iv] and 1968 [3 VII], respectively. This information was complemented by careful prospective and retrospective follow-up procedures in the interval periods allowing for the collection of detailed information over a 5-yr period on 10,000 subjects. Among the advantages of this study have been the large numbers of adult males originating in widely scattered areas of the globe who were examined by standardized pretested procedures with defined criteria of diagnosis. The results of the prevalence phase of the study were accepted with caution owing to the inherent biases of this type of survey [2] so it will be interesting to see if, and in what way, the variations in incidence differ from those of prevalence. In this paper we present data on the prevalence, incidence and mortality. STUDY DESIGN AND METHODS The characteristics of the study population and design of the project have been described fully elsewhere [l] so that only a few of the more relevant points will be recapitulated here. The study population was chosen by a random selection of permanent employees within defined strata of the government and municipal workers. These strata were Reprint requests to: J. H. Medalie, Department of Family Medicine, Building 130, Sheba Hospital, Tel Hashomer, Israel. Supported by P.L. 480 Counterpart Funds, Research Agreement No. 375106. 63

64

J.H. MEDALIE~~U~

based on: (1) Sex: males only; (2) Age: those aged 40 and over in 1963; (3) Place of geographic regions were chosen and to insure adequate representation and reasonably comparable numbers a varying sampling ratio was employed ; (4) Place of work: confined to the large urban areas of Tel Aviv, Jerusalem and Haifa. The response rate to the 1963 prevalence examination was 86.2 per cent of the 11,876 subjects invited to participate, i.e. 10,232. Comparing a sample of the non-respondents and respondents, it was found that the former were slightly older, reported slightly more heart attacks and associated diseases and had more unpleasant previous contacts with medical personnel and institutions. For various reasons (errors of identification, etc.) (1) it was decided to omit data of certain individuals, leaving 10,059 subjects for the subsequent follow-up and analysis. The response rate and disposition of these 10,059 subjects are shown in Table 1. Note that 98 per cent of the survivors of the 10,059 subjects were re-examined 5 yr later in 1968, and knowledge whether the subjects were alive or dead was available on everyone.

birth: six international

TABLE1.

DISPOSITIONOF SUBJECTS DURING5-yr FOLMW-UP PERIODFROM1963 TO 1968

Place of birth

Israel Pastern Europe Central Europe Southeastern Europe Middle East North Africa Total

Number examined in 1963

Number died from 1963-68

Number alive but not examined*

Number examined in 1968

(4

@I

6)

(4

Per cent exam in 1968 d [ a-b

1431 1928 1374 1735 2372 1219

49 ;:

42 36 29 z

::

21

1340 1820 1312 1662 2288 1166

97.0 98.1 97.8 97.8 98.7 98.2

10059

276

195

9588

98.0

36

1

*Includes subjects who were out of country at time of examination

The methodology of the study has been detailed in seven methodological manuals [3] published over the years but a few points will be emphasized. The first is that of Quality Control of procedures, particularly in respect of interobserver variation [4, 51.

The second point is the fact that the survey ECG’s were recorded simultaneously on paper and magnetic tapes. The latter were sent to Washington (to Dr. C. Caceres of the Instrumentation Unit, Heart Disease Control Program, U.S. Public Health Service) where they were converted to a digital record for use as input to a digital computer [6]. Printouts were obtained with the measurements of the different components of the tracing as well as a diagnostic interpretation for each subject. A comparison of the ECG interpretations of six of the project physicians and the computer output indicated quite considerable disagreement. After careful study of the bases of these disagreements, the following operational plan was adopted: All the ECG’s interpreted by the computer as ‘Abnormal’ (in whatever respect) plus a 20 per cent sample of those diagnosed as ‘Normal’ were re-read independently by two cardiologists after an intensive joint training program. Where they agreed,

Myocardial Infarction

Over a Five-Year Period-I.

65

their diagnosis was accepted; if there was any disagreement, the tracing was reviewed by our coordinating cardiologists who decided on the final diagnosis. The latter procedure (i.e. two physicians independently interpreting each ECG with their disagreements going to arbitration) was also adopted for all survey ECG’s where for any reason there was no tape recording, as well as for ECG’s obtained from hospital or other sources as part of the follow-up procedure. The diagnostic criteria used in the electrocardiographic interpretations (see Appendix) were developed by the project cardiologists and differ somewhat from the Minnesota code. Each ECG was classified into one of the six major classification codes, viz: left bundle branch block; probable infarct; possible infarct; myocardial ischemia; non-specific T-wave changes and none of the previous categories or normal. In addition other abnormalities such as left ventricular hypertrophy, arrhythmias, etc., were noted. The3nal diagnosis of myocurdial infarction was based on : (a) Definite myocardial infarction (1) An ECG interpretation

of probable or possible infarct.

(2) Autopsy findings showing definite evidence of recent myocardial infarction and/or coronary thrombosis. (b) Probable myocardial infarction (3) Sudden death, i.e. death occurring within 1 hr of onset of symptoms in a person who was not hospitalized or confined to bed. In other words, it was an unexpected death. Autopsy studies have shown that the majority of these are due to myocardial infarction (see Discussion). (4) A composite of clinical, laboratory, and ECG diagnosis. In subjects who were hospitalized and in whom the composite picture of clinical signs and symptoms, changes in laboratory findings (transaminase, sedimentation rates, leucocytes, etc.) and ECG ischemic changes, together, led to the diagnosis of probable myocardial infarction. The interval follow-up morbidity procedures consisted of: (a) A retrospective follow-up of all study subjects who gave a history of a heart attack at a survey examination, but whose ECG taken at that same survey examination did not show definite signs of probable or possible infarct. The hospital summary and ECG tracings were obtained and reviewed by our project physicians in the manner described earlier. (b) A prospective follow-up was done for part of the total period by having a ‘contact man’ in each government department or subdepartment report at regular intervals on the absence from work of any study subject for a period of 3 weeks or more. Personal contacts were also made with all subjects who left the government service or had retired since the 1963 examination [3-Vol. V]. Each of these subjects was then contacted and a medical or hospital report with ECG’s was obtained for each 3-week or more absence or illness period for retired subjects.

J.H. MEDAUEet al

66

Mortality.follow-up was obtained by:

(1) Obtaining a duplicate punch-card from the central government

Bureau of Statistics for all males (aged 40 and over) in the country who died during the period under review and matching these by identity book number to our study population.

(2) Investigating all subjects reported by their employers as having died. (3)

Checking all those who changed their place of work.

(4)

Writing to those subjects who had gone overseas.

(5)

Following-up all non-respondents

to the 1965 and 1968 survey exams.

Copies of death certificates, hospital summaries and autopsy reports were obtained on every notified death. Where the death had occurred at home, the subject’s personal physician was contacted and rarely, when no other reliable source of info~ation was available, the deceased’s family too. Despite this effort a certain number of deaths remained with the diagnosis of ‘cause unknown’ especially if no autopsies were performed. The diagnosis of myocardial infarction on the death certificate was not accepted unless other evidence (see earlier) was available on which to assure the diagnosis. When no other evidence was available, the cause of death for our survey purposes was recorded as ‘unknown’. For the incidence phase of the study all subjects were considered at risk excluding those who : (1) were diagnosed as having myocardial infarction in 1963 (by previously defined criteria), (2) those with left bundle branch block, and (3) those whose diagnosis in respect of myocardial infarction was unknown. RESULTS

The prevalence (1963) and 5-yr incidence rates (1963-1968) are set out in Table 2. The rank-ordering of the areas of birth in the prevalence survey, with Central and Eastern Europe having the highest rates, North Africa and Middle East the lowest and Southeastern Europe and Israeli-born in the middle, is maintained in the incidence rates, although not as widely dispersed. The variation among these areas of birth is statisti~lly si~ificant for both the prevalence and incidence results. Table 3 shows the incidence data from Table 2 classified into three age groups. The incidence rate for those XL59 yr is about twice that of those 4049 and one-half as large as that for those over 60 yr. TABLE2. AGE-ADJUSTED PREVALENCE AND INCIDENCE RATESOF MYOCARDIAL INFARCTION BY AREA OF BIRTH

Area of birth

Israel Eastern Europe Central Europe Southeastern Europe Middle East North Africa Total Significance: p

Age-adjusted prevalence/1000 1963

26 39 37 24

Age-adjusted incidence/1000 5 yr (1963-68)

Annual average

45 49 50 45

9.0 9.8 10.0 9.0

-ii 44

7.4 8.0 8.7

15

16 27 <:O.Ol

co.05

29 20 14

63

726 518 141

1385

Age in 1963

40-49 m-59 6Of

Total

( )=Less

21

56 25 102

762

822 249 1833

40

45

9.0

45

1K

MI cases

No. at risk

Rate

E. Europe

722 485 113 1320

28

68 100 56

9.8

49

1E

No. at risk

Rate

35 16 65

14

MI cases

C. Europe

10.0

50

72 142 49

19

Rate per 1000

683 180 1687

824

No. at risk 29 57 89 47

24 39 16 79

9.0

45

l%l

MI cases

Rate

S.E. Europe

731 164 2338

1443

No. at risk

34 17 79

28

MI cases

7.4

37

47 104 34

19

l?&l

Rate

Middle-East MI cases 19 18 2 39

No. at risk 884 284 33 1201

8.0

40

63 (61) 32

21

l=

Rate

North Africa

MYOCARDIALINFARCTIONINCIDENCE(INCLUDINGSUDDENDEATH) 1963-1968

than 50 at risk and less than 10 cases

Average annual incidence

Age-adjusted total

MI cases

Israel

No. at risk

TABLE 3.

3523 880 9764

5361

No. at risk

427

202 90

135

MI cases

Total

8.7

44

;z.

2

d

1 w cr! _.

i;

25 57 102 44

1E

E F $

Rate

J. H. MEDALIE et al

68

The decision to divide the study population into geographical areas of birth was based on the well-known differences in habits such as diet; physiological parameters such as blood cholesterol; and morbidity and mortality statistics between the various groups of the population [l]. The reason for six areas was based partly on the above differences as well as for historical reasons which led to stable isolated homogeneous communities in some places and heterogeneous mobile ones in others [7]. To validate this in respect of myocardial infarction, we examined the rates for individual countries (Table 4) within the wider areas. The only geographical area of birth in which there was significant inter-country variation (~~0.05) was in the Middle East, where the low rates of those born in Yemen, Aden and Iran contrasted strongly with those from Turkey, Syria and Lebanon. TABLE4.

MYOCARDIAL INFARCTION INCIDENCE RATES(1963-1968) BY COUNTRY OF BIRTH

Area and country of birth

Number at risk

Number of MI cases

Age-adjusted rate/1000

Average annual age-adjusted/l000

Israel

1385

63

45.0

9.0

Eastern Europe Russia Poland

566 1267

55.9 47.8

11.2 9.6

Central Europe Germany Austria Czechoslovakia Hungary Southeastern Europe Yugoslavia Rumania Bulgaria Greece

496 189 369 265

26 11 17 11

47.5 50.1 53.6 43.3

9.5 10.0 10.7 8.7

102 1231 282 72

6 55 12 6

66.8 42.8 40.1 (88.5)

13.4 8.6

Middle East Afghanistan Aden Yemen Iraq Lebanon Iran Turkey Syria

22 132 383 1149 32 157 296 168

0

North Africa Egypt Tunisia Morocco Libya Algeria Total-all countries

536 102 430 98 35 9764

c---j

(1;::)

(-1

2 6 38 6 4 14 9

(21.4) 15.9 37.6 (148.6) 25.7 51.6 65.1

(2;:;) 5.1 10.3 13.0

18 5 13 2

39.0 57.3 44.1 (18.5) (-) 43.7

7.8 11.5 8.8 (3.7) (-) 8.7

427

(4.3) 3.2

Note: ( ) Rates of countries with less than 100 at risk or less than 5 cases

Only 3.3 per cent of the total study population had been in Israel for less than 10 yr when the study began [l], so there was no purpose to be served by trying to compare recent arrivals with more veteran settlers. The incidence rates of the subjects who immigrated from Europe on the one hand and the Middle East or Africa on the other, are compared with the Israeli-born adults

Myocardial Infarction

Over a Five-Year Period-I.

69

whose fathers originated from the same areas of birth as we11as the Israelis born of Israeli-born fathers, i.e. second generation, in Table 5. Note that the incidence rates are higher for the first generation locally born subjects wherever their family origin was, whereas the second generation Israelis have the lowest rate of all. TABLE 5. INTER-GENERATIONAL VARIATION'IN MYOCARDIAL INFARCXON INCIDENCE (1963-1968)

Number at risk 1.

2.

3.

Immigrants Born in Europe Born in Asia/Africa Total : All immigrants

Number of MI cases

Annual age-adjusted incidence rate/1000 at risk

4840 3539 8379

246 118 364

9.4 7.7 8.7

377 326 703

23 14 37

11.6 9.1 10.4

565

21

7.5

First generation Israeli-born* Fathers born in Europe Fathers born in Asia/Africa Total : first generation Second generation Israeli-born* Fathers born in Israel

*The Israeli-born excludes 117 whose fathers’ birthplace is unknown or whose father was born outside of Europe, Asia or Africa. Of these 117, 5 developed infarcts

The well known significant increase of myocardial infarction rates with rise in age as first shown in Table 3 is detailed for both the prevalence and incidence figures in Table 6 with the former rising more steeply than the latter. Turning to general mortality of all 10,059 subjects who were examined in 1963 (Table 7), a number of points stand out:

(1) An approximate annual crude mortality rate (all causes) of 5.5 per 1000. (2) The significant variation (p < 0.02) between the areas of birth with Israelis and Eastern Europeans having the highest average age-adjusted Southeastern Europeans have the lowest.

rates while

(3) The major causes of death are: (a) myocardial infarction and sudden death, 35.2 per cent of all deaths; (b) malignancies, 23.9 per cent; (c) cerebrovascular accidents, 6.9 per cent; and (d) trauma (accidents and suicide), 5.1 per cent. (4) Fourteen per cent (38) of all deaths are sudden (less than 1 hr) while another 7.3 per cent (20) occurred between l-24 hr. TABLE 6. AGE-SPECIFICPREVALENCE AND INCIDENCE RATESOF MYOCARDIAL INFARCTION

40-49

Prevalence (1963) Number of subjects MI rate/1000 Incidence (1963-1968) Number at risk MI rate/1000 Average annual incidence

-

Age in 1963 50-59

60 and over

All ages

5424 10.0

3672 37.6

963 85.2

10059 27.2

5361 25.2 5.0

3523 57.3 11.5

880 102.3 20.4

9764 43.7 8.7

in 1963

37.3

34.2 31.4 6.3

32.9

6.6

average annual mortality rate =

2i 2 8 9

15 12

1928 72

E. Europe

Age-adjusted total mortality rate/1000 Period of observation 5 yr

4.8

24.0

24.0

10 3 1 6 6 5 2

1374 33

3.9

19.7

20.8

9 2 4 6

0

10 5

1735 36

S.E. Europe

5.2

25.8

22.8

3 7 2 15 3 15 9

2372 54

Middle East

(1963-1968) BYAREAOFBIRTH

C. Europe

TOTALMORTW

13 6 7 14 1 4 4

1431 49

Number died x 1000 Number at risk

( ) Rates based on small numbers

tApprox.

*Total mortality rate/looO=

Age-adjusted total mortality rate/1000 Approx. average annual ageadjusted mortality rate/lOOOt

Causes of death: (1) Myocardial infarction (2) Sudden death (under 1 hr) (3) Cerebrovascular accidents (4) Malignancies (5) Trauma (accidents, etc.) (6) Miscellaneous diseases (7) unknown Total mortality rate/lOOO*

Total study population Deaths

Israel

TABLE 7.

(8.9)

(44.6)

26.3

5 3 2 0 8 6

8

1219 32

N. Africa

5.5

27.4

27.4

59 38 19 66 14 44 36

10059 276

Number

Total

21.4 13.8 6.9 23.9 5.1 15.9 13.0

100.0

Per cent

k b % f?.

i

2

Myocardial Infarction

Over a Five-Year Period-I.

71

Using Israel national figures on male mortality from 1965 (the mid-year of the survey), deaths in the study population would have been 345 over a 5-yr period, if the study population had been representative of the country’s adult males of this age. The observed figures were 276, being exactly 80 per cent of the expected total figure and less than 100 per cent in every age group (Table 8). This was probably to be expected because the method of selection of the subjects was that they were well enough to be gainfully employed (see under Discussion). TABLE 8. OBSERVED AND

Age group 40-44 45-49 50-54 55-59 60+ Total

Israel male mortality rate in 1965/1000* 2.7 3.6 7.0 11.6 20.3

EXPECTED MORTALITY (1963-1968)

Number of subjects at risk

Expected

Number of deaths Observed

O/E

3317 2107 2180 1492 963

45 40 15 85 100

33 30 68 71 74

0.73 0.75 0.91 0.84 0.74

10059

345

276

0.80

*Based on Israel national figures for 1965, the mid-year of the survey [38]

Of the 9764 subjects at risk as shown in Tables 4 and 6, 427 were diagnosed as having a first myocardial infarction, and of these, 68 died during the 5-yr observation period. Twenty-four of the 68 (35.3 per cent) died suddenly within 1 hr (Table 9). The remarkable point of the case-fatality rate is the extremely low figure of 15.9 per cent over a 2.5-yr average observation period. The variation in the case-fatality rate between the areas of birth is not significant and could be due to chance. Although the rise with age is statistically significant (Table lo), the figures of the older age groups do not even reach 20 per cent. In Table 11, the basis of diagnosis of the 427 subjects who developed their first infarct after 1963 is presented. The major feature is that 170 of these had not been clinically recognized prior to the subject’s examination in the survey. (See further remarks under Discussion.) The case fatality rate of subjects whose infarcts had been clinically recognized was 66/257 or 25.7 per cent, over the 2.5-yr average observation period, whereas the case fatality rate of subjects with ‘silent’ infarcts was very low, 2/170 or 1.2 per cent. DISCUSSION

Due to small numbers of cases, most epidemiologic studies have combined myocardial infarction and angina pectoris into one group known as coronary or ischemic heart disease. This tends to obscure the epidemiologic differences between these two conditions [8,9]. In our study the large number of subjects observed for 5 yr produced sufficient numbers of both these conditions to allow us to separate them; here we discuss first myocardial infarction only. The validity of the incidence rates of myocardial infarction in a long-term prospective study depends on a number of factors, three of which deserve special emphasis. These are the criteria of diagnosis; the participation in the examination and the C

7 1 17 16.7

9

1833 102

E. Europe

2 1 9 13.8

6

1320 65

C. Europe

BYAREA

4 1 13 16.5

8

1687 79

S.E. Europe

(1963~1968)*

*Average period of observation=Z.fi yr because the 427 developed their infarcts during the entire J-yr period. Number of deaths of new subjects with MI *Case fatality rate= Number of new subjects with MI

1 10 15.9

:

Deaths of MI cases From MI

Sudden deaths (under 1 hr) Other causes Total deaths tie fatality rate per cent

1385 63

Israel

CASE-FATALIZY 0~~~~~~~~~~0~s

Total at risk Number of MI casts

TABOO.

1 9 11.4

:

2338 79

Middle East

OFBIRTH

10 25.6

;

4

1201 39

N. Africa

24 8 68 15.9

36

9164 427

Total

! <

P

k

z

Myocardial Infarction

Over a Five-Year Period-I.

73

TABLE 10. CASE-FATALRYOF MYOCARDIALINFAR~ON (1963-1968)’ BY AGE

Age (yr) 41-49 Total at risk Number of MI cases Deaths of MI cases From MI Sudden death (under 1 hr) Other causes Total deaths t&se

fatality rate per cent

*Average period of observation=2.5

So-59

Total

5361 135

3523 202

6f+ 880 90

9764 421

8 7 0

18 13 6

10 4 2

36 24 8

15

37

16

68

11.1

18.3

17.8

15.9

yr

Number of deaths of new subjects with MI tCase fatality rate = Number of new subjects with MI

extent of the coverage of the screening and follow-up procedures; and the number of previously unrecognized infarcts found. The ECG criteria were specified clearly (Appendix) and are comparable but slightly different (somewhat stricter) from the Minnesota Code. The computer reading of the ECG’s added to the reliability of the interpretations but following a pretest [lo] the validity of the abnormal diagnoses was not accepted without further independent readings by at least two specially trained physicians. The inclusion of sudden death of less than 1 hr from onset of symptoms as part of the myocardial infarction group, is we believe, justified, in that studies have demonstrated that the overwhelming majority (90f per cent) of sudden deaths in less than 1 hr that came to autopsy were due to coronary heart disease, whereas only a little over 50 per cent were attributable to coronary disease in sudden deaths in which the acute episode lasted over 1 hr [1 1, 121. The participation in the tist stage of the survey was 86.2 per cent which compares favorably with many of the long-term American studies which had response rates of less than 70 per cent for the first examination [13-15-J. The latter studies also reported between 89 and 95 per cent participation in the 4 and 5-yr follow-up examination, which is close to the 98 per cent re-examined in this project, 5 yr after the beginning. In addition we had information of the remaining 2 per cent in that we knew whether they were alive or dead. Comparing this population’s rates with studies from other countries is a hazardous undertaking due to the differences in the age structure of the subjects, diagnostic criteria and completeness of follow-up procedures. The latter is an important distinction because some studies rely on clinically diagnosed patients for their case finding, whereas others use population screening procedures in addition. In Table 12 incidence rates of first myocardial infarctions are reported and compared to our findings, which we have recorded in two ways. The first is the rate for clinically recognized infarcts (5.3/1OOO/yr) and comparable to the North Dakota study [26]. The second is the rate for all types of first infarcts detected, whether ‘silent’ or not (8.7/ lOOO/yr) and is in the same high class as studies like Framingham. This high rate of 8.7/1000 is the average of six areas of birth between which there is a significant variation in rates. Even the ‘lowest rate area’-the Middle East, has an incidence rate

257

421

Grand total (a)+(b)

YSilent infarcts’=Subjects

evidence and occasionally

24

1 19 23 44

1

1 1 -

11

18 -I 1 2 4 43

< 1 hr

autopsy

68

5 19 66

1

12 19 8 1

Total

not aware of having infarct or infarct not accepted by survey

suggestive clinical and laboratory

94 103 31 1 1 3 5 19

Probable infarct Possible infarct Myocardial ischemia (+ CLA)* LBBB ( + CLA) Non-specific T-waves (+CLA) None of above (+CLA) No ECG available ( +CLA) Sudden death as only evidence Sub-total

*+CLA=With

n

ECG diagnosis

Died >l hr

(a) Subject aware of infarct

2 4 19 19

-

-

3 8 2

Number autopsied

170

-

-

18 152 -

n

1

1

1

-

1

Died >l hr

(b) ‘Silent infarcts’t
INFARCTIONCASES TABLE 11. BASISOF DIAGNOSISOF 421 MYOCARLXAL

1 2

Total

-

1 -

Number autopsied

F P z P

$

2

Myocardial Infarction TABLE 12.

Over a Five-Year Period-I.

75

INTERNATIONAL COMPARISON OF INCIDENCE RATES OF FIRST MYOCARDIAL AMONGMALES

INFARCTIONS*

Average annual incidence/ 1ooot .-

Study

Number at risk

Number of MI cases

Years of obs.

Yugoslavia [24] Greece [21] Japan [25]

1545 1207 2267

8 10 21

5

40-59

I.1

:.9

40-59 40-70+

I.6 2.8

40-59 4&59 4&59 4fL55 35-75

2.8 3.0 4.4 4.6 4.7

Agerange

(Ave.) Yugoslavia [ 171 Italy [23] Italy [19] U.S.A.-Chicago (W-E) [14] U.S.A.-N. Dakota [26] Israel IHD project (known infarcts} Finland [ 181 Netherlands [20] U.S.A.-Middlesex Co. [27] U.S.A.-Railway j16J U.S.A.-N.Y. (H.I.P.) [28] U.S.A.-Chicago 1291 England-Med. Pratt. [30] U.S.A.-Western Collab. [31] Israel IHD project (all infarcts) U.S.A.-Fr~in~h~ 1321 U.S.A.-Framingham [33] England-Busmen [34]

1365 758 1695 1989 19830

: 5

4.5

9764

257

5

40-70

5.3

1620 864 11559 2454 ilooooo 665 7000 3182

44 28 74 77 613

5

40-59

5

40-59 35-64 40-59 35-64 50-59 40-64 39-59

5.7 6.0 6.4 6.5 6.6 7.0 7.0 7.3

z 104

9764

427

12824 1037 667

234 62 40

5

3 4 5 4.5

14 6 5

40-70

8.7

40-69 45-62 30-69

G 10.0 12.0

*Myocardial infarction=Myocardial infarction and sudden death as defined in each study, except for U.S.A.-Chicago (W-E) which excluded sudden deaths IThese figures are taken from the reports of the studies or were calculated from them. Owing, however, to the ambiguity of some reports, some of these figures might be inaccurate-if so, our apologies f ] Figures in brackets are the reference numbers Some of the above studies, e.g. U.S.A.-N. therefore do not include ‘silent infarctions’

Dakota were not based on population

examinations,

which is very high on the international map! However, there is a substantial intra-area variation within the Middle East, where the Yemenite-born have incidence rates which are reasonabIy low by international standards. The rate of immigrants from Europe and Asia-Africa was then compared with Israeli-born subjects from fathers born in Europe or Asia-Africa. In line with the Chicago [29], Australian [35], Hawaiian [36] and Framingham [37] experience, our first generation Israeli-born adult males had higher incidence rates than the immigrants from the same areas of birth as their fathers. It was not surprising that the Asia-Africa rates rose, but it was interesting to find the already high rates of the European-born went still higher among the first generation locally born subjects. This was unlike the New York [28] results which showed the immigrants from Europe having higher rates than first generation Americans; this heId for both Jews and Catholics. Going one step further, we found that second generation Israeli-born subjects (i.e. whose

76

J. H. MEDALIEet

al

fathers had also been born in Israel) had a reduced incidence rate and dropped to the level of the Asia-Africa immigrants. However, these variations must be accepted with caution as a few more infarct cases in one group or another could change the rates considerably. Therefore at this stage we prefer not to speculate as to the reasons for the variation, but to await further confirmation. Having established that the study population has a high myocardial infarction incidence rate we now turn to examine their mortality experience. The major causes of mortality among the 10,059 subjects examined in 1963 and followed for 5 yr (Table 7) are similar to most countries in which acute infective conditions have ceased to play an important role. The total mortality rate rose markedly with age and varied significantly (p=O.O2) among the six areas of birth with Israeli-born being the highest and Southeastern Europeans the lowest. These results differed from the national figures in that the overall mortality was 80 per cent of the expected and all the areas similarly were below 100 per cent with Israeli-born being 0.91 and Asia-Africa together, being 0.77. The fact that the mortality of the study population differs somewhat from the total population of Israel seems to be a characteristic of all long-term studies for the first few years and might have one of two explanations. The first is that these government permanent employees do, indeed, differ from the total population-it excludes, for example, those people on social welfare relief, the owners of private businesses, most of the farming sector of the community and all persons too sick to be regularly employed. The participants also have the security of permanent employment and because of selection criteria were probably somewhat healthier than the general population. All study populations who are employed groups, insurance policy holders or volunteers should therefore have a more favourable general mortality than the total population, at least in the first few years of the study. Another explanation to be considered is that whenever a selected group of the population is brought under periodic health supervision with a feed-back to their personal physicians for consideration of new conditions discovered, and follow-up of previous ones, the resulting improvement in medical care may be reflected in a reduction of the overall mortality rate. If this hypothesis is correct, it should occur not only in all large scale on-going studies but even in groups at high risk. It is interesting to note, therefore, that in Minnesota where a group of senior business executives were chosen as a high risk group for follow-up, the death rate among them was remarkably low [43]. Leaving this just as a thought for others to examine, we shall turn to the mortality experience of those with infarcts. There were remarkably few deaths among the 427 subjects who developed a myocardial infarction in the 5 yr. The major cause of death of the 68 fatalities (15.9 per cent case fatality rate) was the direct result of the myocardial infarction or sudden death presumably from the same cause. Only eight subjects (11.8 per cent) died from causes definitely unrelated to their previous infarction. Despite the difficulties and limitations inherent in comparing international studies, one is struck by the fact that the results quoted in Table 13 show similar patterns. Between 25 and 30 per cent of all patients with first attacks of myocardial infarction die within the first day following onset of symptoms. This holds for European studies as well as North American despite the fact that in some places in Europe investigators believe that ‘men with coronary disease are less likely to die early from the disease’

Myocardial Infarction

17

Over a Five-Year Period-I.

[8] and indeed the 15.8 per cent of all myocardial infarctions (first and recurrent) who died in the first hour reported from Edinburgh [42] seem to corroborate this view. On the other side of the globe, studies from Japan [25] show a very low incidence and early mortality rate but at the end of 5 yr 18 of 51 new cases of myocardial infarction had died-i.e. a mortality rate of 35.3 per cent. However, since these figures from Hiroshima combine males and females in one set of results, the male rate alone is not available. TABLE

13.

INTERNATIONALCOMPARISON

Study

OF CASE-FATALITY RATESOF AMONGADULTMALFS

Age-range

H.I.P. (N.Y.) [39] Middlesex Co. [27] Framingham [33] Winnipeg [4O] Chicago [29] Du Pont [42] Medical Practitioners [30] Albany [43] Busmen [34] Israel ischemic heart disease project (a) Clinically diagnosed infarcts (b) All infarcts

-65 35-64 30-62 Ave. 46 50-59 17-64 40-64 39-55 30-69

Within 1 hr

FIRST MYOCARDIAL

INFARCTIONS

Deaths as per cent of all MI cases Within Within In 2.5 yr 24 hr 30 days 30.8

27.0 27.3 22.0

29.5

25.2 25.0 20.0 17.5

36.0

28.0* 30.0 38.0

25.0t

25.7 15.9

40-70 40-70

*Time period not clearly specified tDeaths within a few days [ ] Figures in brackets refer to references

With this background of international studies, the remarkably low case fatality rate of this Israeli study stands out most significantly. Whichever way one examines the figures, a rate of 15.9 per cent for all infarcts and 25.7 per cent for previously known infarcts after 2.5 yr of average observation is almost unbelievable. An extremely high myocardial infarction incidence with an extremely low case fatality rate has, as far as we are aware, not been reported before. Questions we asked ourselves are: Is the general mortality very low? Do the males die primarily from other causes and not from cardiovascular diseases? Do patients with infarcts receive medical aid extremely rapidly-within minutes? Do our subjects have a great deal of physical exercise? Most of these have been answered in the negative. However, it does seem that Israel has a low mortality rate from all causes as compared to the United States. Using data from various sources [l, 461, a calculation of the mortality rates for all causes is as follows: Israel

United States (males 1967) Age 4@64

4of

Crude rate Age-adjusted project Crude rate

12.9/1000 to Israel heart

Israel heart project

5.5/1000

National figures : Crude rate

14.9/1000

11.2/1000 27.3/1000

J.H. MEDAJJE~~ al

78

In addition to this relative overall low mortality, could it be that because of our more complete coverage we have found and included so-called milder infarct subjects who tend to have lower mortality rates ? Are ‘silent infarcts’ these milder ones ? Have subjects with ‘silent infarcts’ a better mortality experience and life expectation than those with clinically recognized infarcts ? The ‘silent infarcts’ include those subjects (Table 14) who were: (1) Asymptomatic. These accounted for 50 per cent of the group. Many in this group had serious associated conditions like hypertension, etc. ; (2) Symptomatic. This group included those (a) with atypical symptoms and (b) probably missed cases; and (3) Not accepted by the survey cardiologists. Three subjects had an infarct diagnosed prior to their survey examination, but their ECG and other results were not accepted by the survey cardiologists as evidence of an infarct. TABLE 14.

DISTRIBUTION OF THE‘SILENT INFARCTS'• F 1965 AND 1968

Number 1. 2. 3. 4. 5.

Asymptomatic: Without any other serious disease/condition Asymptomatic: With associated serious condition/disease Symptomatic: Atypical symptoms or missed diagnosis Previous clinical diagnosis rejected by survey cardiologists Type unknown Total

Percentage

32 53 12 3 10

18.8 31.2 42.3 1.8 5.9

170

100.0%

The percentage of these ‘silent infarcts’ of all infarcts was a very high 39.8 per cent (Table 15), almost double that found in the Framingham study [47]. This high percentage varied between the different areas of birth with the Central-European-born having the lowest (27.7 per cent) while the Middle East and Southeastern Europeans were at the other extreme with about 50 per cent of all their first infarcts being of the ‘silent’ type! Of the 170 ‘silent infarcts’, there were 54 found at the 1965 examination and 116 at the 1968. This means that the mortality experience, at this point, can only be gauged by the 54 cases found in 1965. Judging by our case fatality figures, we would have expected at least eight deaths among these 54 subjects. In reality, there were only two in the period 1965-1968. The numbers are small so that at this stage we can only say that our results suggest that ‘silent infarcts’ are of a milder variety with a better mortality experience. If this proves to be the case, it would help to explain some of the low case fatality rates found among those who had a first myocardial infarction in our study population. Finally, it seemed of interest to examine the infarct and mortality experience of Jews living outside of Israel; this, despite the fact that Jews are not a homogeneous group either historically or biologically [43-45]. Nevertheless, it was interesting to note that a calculation based on New York figures [28] shows a somewhat similar picture (Table 16)-a high incidence rate among Jewish males with the lowest case fatality rate in 48 hr. However, this latter rate is still within the range of most international studies and is significantly higher than the Israeli study reported here-23.5 per cent in 48 hr as compared to 15.9 or 25.9 per cent over 2.5 yr! As a concluding thought, could it be that this overall relatively low male mortality and extremely low myocardial infarction case fatality, together, contribute to the

All infarcts: Number

33.3

Silent infarcts as per cent of all infarcts

East

27.7

18

3 1 12 2

7.1

47

10.0

65

Europe

Central

SE.

49.4

39

9 1 29 -

4.6

40

9.0

79

Europe --

51.9

41

14 25 2

3.6

38

7.4

79

East

Middle

North

--

41.0

16

4 11 1

(3.8)t

23

8.0

39

Africa

gives an unreliable figure owing to rarity of numbers

34.3

35

8 4 19 4

6.6

67

9.8

102

Europe

*Silent =Subjects not aware of having infarct or infarct not accepted by survey

tThe straight rate is 3.8/1000 which on age-adjusting

rate for areas of birth

21

All silent infarcts

*Average annual age-adjusted

8 2 10 1

6.0

42

9.0

63

ECG diagnosis 1965 Possible infarct Probable infarct 1968 Possible infarct Probable infarct

Silent infarcts*

Annual rate/lOOO*

Known infarcts: number

Annual rate/lOOO*

Israel

TABLE 15. F~VEYEARINCIDENCEOFKNOWN,SILENTANDTOTALMYOCARWIALINFARCTIONSBY

39.8

170

46 8 106 10

5.3

257

8.7

427

Total

AGE

38.5

52

11 3 36 2

3.1

83

5.0

135

40-49

ANDBIRTHPLACE

36.6

74

22 2 44 6

7.3

128

11.5

202

50-59

48.9

44

13 3 26 2

10.5

46

20.4

90

60+

80

J. H. MEDALIEet al

smaller difference between the sexes in respect of life expectancy? Females in Israel have a life expectancy of 2.7 yr more than their males (73.2-70.5 in 1965), whereas in most Western countries the difference between the sexes at that time was about 5 yr. TABLE 16. MYOCARDIALINFARCTIONINCIDENCEAND EARLY MORTALITY BY RELIGIOUS AFFILIATION(MODIFIEDFROM H.I.P. STUDY [28]) Religious affiliation

MI incidence/1000 age-adjusted

Deaths in 48 hr x 100 first MI cases

Jewish

6.56

23.5

Catholic

4.54

37.7

Protestant

5.03

32.6

SUMMARY

A 5-yr (1963-1968) follow-up of 10,059 male government and municipal employees of Israel aged 40 and over, divided into six regions of birth-Central Europe, Eastern Europe, Southeastern Europe, North Africa, Middle East and Israel-was completed. In the first survey (1963), 86.2 per cent of the invited sample participated in the examination. They were re-examined in 1965 and 1968, with 98 per cent of the original respondents participating in the final examination. There was complete coverage in respect of knowing whether the subjects were alive or dead. The results revealed a significant variation between the birth-areas in respect of age-adjusted prevalence and incidence rates of myocardial infarction as well as total mortality for all causes. The infarct incidence rates were higher in the first generation Israelis than in immigrants from the same areas of origin, but were substantially lower for second generation subjects. The age-adjusted annual myocardial infarction rate of 8.7/1000 at risk, places this study population among the highest in the world. In contrast to this, the case-fatality rate of 15.9 per cent after an average period of 2.5 yr of observation is one of the lowest in the world and contrasts markedly with many international studies which report higher figures for deaths within 1 hr after onset of symptoms. One of the possible reasons for this apparent anomaly might be the fact that 39.8 per cent of the 427 first myocardial infarcts were of the ‘silent’ type. The latter seem to have a lower mortality experience than the clinically recognized infarcts.

REFERENCES Groen JJ, Medalie JH, Neufeld HM et al: An epidemiologic investigation of hypertension and ischemic heart disease within a defined segment of the adult male population of Israel. Israel J Med Sci 4: 177, 1968 Medalie JH, Neufeld HN, Riss E et al: Variations in prevalence of ischemic heart disease in defined segments of the male population of Israel. Israel J Med Sci 4: 775, 1968 Methodological Research Manuals published by the National Heart Institute (U.S.A.), Hadassah Medical Organization (Israel), and Ministry of Health (Israel), Jerusalem, Israel Volume I: Examlnatlon Procedures. Medalie JH, Bachrach C, Smith H et al: 1963 Volume II : Coding and Poncbing Instructions with Key of Codes and Classification of Variables. Bachrach C, Smith H, Kay PAJ et al: 1964 Volume III: Food Composition Tables. Balogh M, Groen JJ, Medalie JH et af: 1964

Myocardial Infarction Over a Ftve-Year Period-I,

4.

5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.

81

Volume IV: Ineidenee Study, 1965. Medalie JH, Tzur B, Tamir S e# al: 1965 Volume V: Follow-up Prneedures. Perlstein T, Sive P, Medalie JH et al: 1967 Volume VI: Sociological Aspects. Shamgar L, La&u A, Medalie JH et al: 1967 Volume VII: Incldenee Study, 1968. Medalie JH, Perlstein T, Tamir S et al: 1968 Medalie JH, Riss E, Neufeld HN ei aJ: Some Praetlcal Problems of Observer Variation In a Large Survey in Cardiology-Current Topies and Progress. Eliakim M and Neufeld HN, Eds. Academic Press, New York and London. pp. lW104, 1970 Medalie JH, Neufeld HN, Riss E et al: The Israel ischemic heart disease project: description and selected prevalence findings. Prnced Tel Hashomer Hospital 6: 41, 1967 Caceres CA, Steinberg CA, Abraham S et at: Computer enteaction of eiectro-cardiographic parameters. Circulation 25: 356, 1962 Medalie JH: Classification of Israeli Jews for medical-scientific purposes. Israel Med J 21: 118, 1962 Epstein FH: The epidemiology of coronary heart disease. J Chroo Dis 18: 735, 1965 Meade TW: The epidemiology of ischemic heart disease. Tram See Occup Med 18: 127, 1968 Neufeld HN, Riss E, Sive PH et al: The use of computerized E.C.G. interpretation system in an epidemiological study. Methods Inf Med 10: 85, 1971 Kuller L, Lilienfeld A, Fisher R: An epidemiological study of sudden and unexpected deaths in adults. Me&&e 46: 341, 1967 Kuller L: Sudden and unexpected non-traumatic deaths in adults. J Chron Dis 19: 1165, 1966 Dawber TR, Moore FE, Mann GV: Coronary heart disease in the Framingham study. AJPH 47: 4, 1957 Paul 0, Lepper MH, Phelan WH et al: A longitudinal study of coronary heart disease. Circulation 28: 20, 1963 Keys A (Editor). Coronary heart disease in seven countries. Circufation 51,4, Supplement 1,197O Taylor HL, Blackburn H, Keys A et al: Five year follow-up of employees of seIected U.S. railroad companies. Ibid pp. 20-39 Buzina R, Keys A, Mohacek I ef al: Five year follow-up in Delmetia and Slavonia (Yugoslavia). Ibid pp. @51 Karvonen MJ, Orma E, Punsar S et al: Five year experience in Finland. Ibid pp. 52-62 Fidanza F, Pudda V, Imbimbo B et al: Five year experience in rural Italy. Ibid pp. 63-75 Van Buchem FS: Zutphen, a town in the Netherlands. Ibid pp. 76-87 ~8~~~is C, Corcondiias A, Dontas AS et al: The Greek islands of Crete and Corfu. Ibid pp.

Kiarura N, Keys A: Rural southern Japan. Ibid pp. 101-l 12 Taylor HL, Menotti A, Puddu V et ai: Five years of follow-up of railroad men in Italy. Ibid pp. 113-122 24. Djordjevic BS, Balog B, Bozinovic L et al: Three cohorts of men followed five years in Serbia. Ibid pp. 123-137 25. Johnson KG, Yano K, Kato H: Coronary heart disease in Hiroshima, Japan. AJPH 58: 1355, 1968 26. Zukel WJ, Lewis RH, Enterline PE et al: A short-term community study of the epidemio~o~ of coronary heart disease. AJPH 49: 1630, 1959 27. Eisenberg H, Feltner WR, Payne GH et al: The epidemiology of coronary heart disease in Middlesex County, Conn. J Chron Dis 14: 221, 1961 28. Shapiro S, Weinblatt E, Frank CW et al: Incidence of coronary heart disease in a population insured for medical care (HIP). AJPH 59,6 Supplement, l-101, 1969 29. Stamler J, Lindberg HA, Berkson DM et al: Prevalence and incidence of coronary heart disease in strata of the labor force of a Chicago industrial population. J Chmn Dis 11: 405, 1960 30. Morris JN, Gardner MJ: Epidemiology of ischemic heart disease. J Am J Med 46: 674, 1969 31. Rosenman RH, Friedman M, Straus R et al: Coronary heart disease in western collaborative group study. J Chron Dis 23: 173, 1970 32. Feinleib M: The Framingham Study: an Epidemiological Investigation of Cardiovascular Disease. Section 7, 1968. Stencilled tables issued by National Heart Institute, Bethesda, Maryland 33. Karmel WB, Dawber TR, Kagan A et al: Factors at risk in the development of coronary heart disease-six years of follow-up experience. Annals Int Med 55: 33, 1961 34. Morris JN, Kagan A, Patterson DC et al: Incidence and prediction of ischemic heart disease in London busmen. Lancet 1: 553, 1966 35. Rose G quoting Stenhouse and McCall-1969 in Current Developments of Atherosclerosis in Europe from ‘Atherosclerosis’: Proceedings of the Second International Symposium. R. J. Jones, Ed. pp. 310-314. Springer-Verlag; Berlin-Heidelberg-New York, 1970 36. Gordon T: Mortality experiences among the Japanese in the U.S., Hawaii and Japan. PubI Health Rep 72: 543, 1957

J. H. MEDALIEet al

82 37. 38a. 38b. 39. 40. 41. 42. 43. 44. 45. 46. 47.

Dawber TR, Kamel WB, Revoskie N et al: Some factors associated with the development of coronary heart disease. AJPH 49: 1349, 1959 Statistical Abstract of Israel No. 19-1968. Central Bureau of Statistics. Government printer, Jerusalem Vital Statistics: Special Series No. 318. Central Bureau of Statistics, Government printer, Jerusalem _ Weinblatt E, Shapiro S, Frank CW et al: Prognosis of men after the first myocardial infarction. AJPH 58: 1329, 1968 Mathewson FA, Brereton CC, Keltie WA et al: The University of Manitoba follow-up study: a prospective investigation of cardio-vascular disease. Canad Med Ass J 92: 947, 1965 Pell S, D’Alonzo CA: Immediate mortality and five year survival of employed men with a first myocardial infarction. New Eng J Med 270: 915, 1964 Fulton M, Julian DG, Oliver MF: Sudden death and myocardial infarction. Circulation 40: 182, 1969 Keys A, Taylor HL, Blackbum H et al: Coronary heart disease among Minnesota business and professional men followed fifteen years. Circulation 28 : 381, 1963 Shapiro HL: The Jewish People-a Biological History. UNESCO, Thone, Liege, Belgium, 1960 Medalie JH, Kahn HA, Neufeld HN et al: Physicians’ Fact Book: Selected Measurements on 10,080 Israeli Males. Published by the Israel Ischemic Heart Project. Jerusalem, 1968 NCHS and Current Population Reports. p. 25. No. 441. March 19, 1970. Table 2. Bureau of the Census, Washington, D.C., U.S.A. Stokes J, III, Dawber TR: The ‘silent coronary’; the frequency and clinical characteristics of unrecognized myocardial infarction in the Framingham study. Ann Int Med 50: 1359, 1959

APPENDIX CRITERIA

FOR

ELECTROCARDIOGRAM

INTERPRETATION

6.

Left bundle branch block (probable): QRS 2 0.12 in any 3 leads and Rd > 0.08 set in leads V. or V. and Sd 2 0.04 set and Ta negative in lead I or AVL or STe of -0.1 mV or deeper in lead I or AVL and no Q in V, or V,

5.

Probable infarct: (a) Consistent 4 (a) plus @) Consistent 4 (a) plus

with anterior myocardial infarction of undetermined Coronary T-waves 3 (b). with acute anterior myocardial infarction STo elevated 2 0.15 mV in 3 or more leads.

Cc) Consistent with diaphragmatic myocardial (1) 4 (b) plus coronary T-waves 3 (b). (2) Q-waves in all three leads II, III and 0.05 set or more, another a duration be l/5 the amplitude of the following

age

infarction of undetermined

age

AVF one of which must have a duration of of 0.04 set or more, and at least one must R.

Consistent with acute diaphragmatic myocardial infarction Q-waves in any two of leads II, III and AVF plus STo elevation 2 0.15 mV in 3 or more leads. Any diagnosis of diaphragmatic myocardial infarction requires a peak-peak voltage of 0.21 or greater in all QRS complexes considered. (4 Consistent with myocardial infarction of undetermined age 4 (a), 4 (b) or 4 (c) plus coronary T-waves 3 (b). (f ) Consistent with acute myocardial infarction Q-waves plus STo elevation of 0.15 mV in 3 leads. (4

4.

Possible infarct: (a) Possible old anterior myocardial infarction (1) R wave I 0.1 mV in leads Va - V, (any two leads) or (2) Q-wave present in lead Vz or V, unless Ra 2 Sa in the same lead (RVH suppresses this diagnosis).

Myocardial Infarction

Over a Five-Year Period-I.

83

(b) Possible old diaphragmatic

myocardial infarction Q-waves in all three of leads II, III and AVF of which two Q-waves must have a duration of 2 0.04 set and at least one of these must be l/S amplitude of following R, or tbe R is absent.

Cc) Possible old myocardial infarction Q-waves in leads I and AVL, each with a QRS voltage 0.21 or greater one Q 0.04 sec. or greater and l/5 the height of R; the other Q 0.03 set or greater or l/5 the height of R.

(4

3.

Parietal block Left axis deviation - 30” or greater and QRS > 0.12 in any two leads (standard, V,, V,).

Myocardial ischemia:

(4

Ischemic T-waves Ta of -0.1 mV or deeper in (1) lead I or V, or (2) 2 leads (excluding leads III, V, and V,).

(b) Coronary T-waves Ta of - 1.O mV or deeper in any one lead (excluding lead AVR).

Cc) Pathological S-T depression (1) STo, STm and STe depressions of -0.1 mV or deeper in any one of leads I, II, AVL, AVF, V1, V4, V,, V,: or (2) STo depression of -0.1 mV or deeper in any three of leads I, II, AVL, AVF, Vs. V4, V, and V,. _. . (This diagnosis is suppressed if heart rate is 100 or more in at least 3 leads). (d) Incomplete left QRS > -0.12 and Sd I 0.04 and absence of 2.

bundle branch block in any 3 leads set and Ta negative in lead I or AVL Q-waves in all the following leads - I, II, AVL, AVF, V, and V,.

Non-specific T-wave abnormality (scalar): (a) Ta < +O.l mV in lead I or V,, or (b) Ta of -0.05

mV or deeper in lead I or V6, or

(c) Ta 2 + 1.O mV in any two leads, or (d) Ta I 0.05 mV or Ta I 0.01 mV in 3 leads (excluding leads III, AVR, V, and V,). Other: P-Pulmonale

Pa 2 0.2 mV in any 2 leads.

P-Mitrale Short PR interval All PR intervals < 0.11 set (one exception allowed and rate less than 100). Conduction defect consistent with Myocardial infarction Emphysema S-l, 2, 3 Syndrome Biphasic complexes in all standard leads i.e. Mean QRS amplitude I 0.15 mV (one exception allowed). Possible conduction defect QRS 2 0.12 in any two standard leads. Right bundle branch block QRS 2 0.12 (any 2 standard leads) and Sd 2 0.04 sec. Lead I or AVL and R’ or QR present V, or V,. Possible right ventricular hypertrophy

RV1 > SV,.

84 A.

J. H. MEDALIEet al Lejt ventricular hypertrophy, probable or possible: (a) AVF voltage consistent with LVH

Ra 2 2.0 mV AVF

(b) AVL voltage consistent with LVH

Ra 2 1.3 mV AVL

(c) Possible left ventricular hypertrophy SVr + RV5 2 3.5 mV or WI + RV8 2 3.5 mV (d) Voltage consistent with left ventricular hypertrophy SV, + RV6 2 4.6 mV or SVr + RVB 2 4.6 mV or WI + RV, 2 4.6 mV or SVI + RV,, 2 4.6 mV B.

Electrocardiographic

low voltage

Neither the height of R wave nor the depth of the S wave must exceed 0.5 mV in any standard lead, at least four standard leads must be present. C.

Atria1 fibrillation Irregular R-R intervals in 5 or more leads that are not low voltage and P amplitude=O.OO in 5 or more leads.

D.

Arrhythmias

(a) Multifocal extrasystoles,

or

(b) Bigemini or Trigemini in any two leads. E.

Atrioventriculur block: first (PR z 0.21 set in any 2 leads, heart rate 60) second and third degree.

F.

Technically unsatisfactory.