Acta Medica Scandinavica. Vol. 172, fasc. 2, 1962

From the Department of Medicine, University of Lund, Allmanna Sjukhuset (Head: Jan Waldenstrom, M. D.), Malmo, Sweden

Continued Studies on Myocardial Infarction in Malmo

Our 1935 to 1954 Material Completed for the Years 1955 to 1959

BY

J. SIEVERS a n d G. BLOMQVIST

Based on a material of 1,612 patients, hospitalized during the years 1935-54 for acute myocardial infarction in Malmo, Sweden, we have, in a number of earlier publications (1-6) presented some epi- demiological, clinical a n d prognostic considerations as to the mentioned con- dition. Though a more comprehensive study on this subject is under prepara- tion (7) we have found it feasible already now to present some findings concerning the cases of acute myocardial infarction hospitalized in our clinic during the sub- sequent 5 year period of 1955-59.

As has been pointed out in our earlier publications, Malmo is a town of now about 220,000 inhabitants with good opportunities for epidemiological research since the town has only one large univer- sity hospital a n d no private ones. The pa- tient material in the hospital is solely derived from the town. Furthermore the autopsy frequency a t the hospital is 92.5 yo which gives good opportunities to check the accuracy of the clinical diagnoses.

Submitted for publication January 15, 1962.

During the years 1935-54 a total number of 1,821 acute myocardial infarctions were hospitalized. Of these 1,530 were primary infarcts, as estimated from the hospital re- cords, 238 second infarcts, 47 third infarcts, 5 fourth infarcts while 1 patient had at least five infarctions. We have now undertaken to go through the hospital record material from the years 1955-59 incl. to follow up the trends found in the earlier 20 year material. During the last 5 year period another 1,067 cases of acute myocardial infarction were hospitalized. Of these 936 were primary infarcts, 120 second infarcts and 11 third infarcts.

A short summary will be given as to the criteria used for the diagnosis of acute myo- cardial infarction. For further details see one of our previous papers (1).

These criteria have been : 1. The observation at autopsy either of a

fresh myocardial infarction or of a fresh cor- onary occlusion in the presence of typical and acute clinical symptoms.

2. Typical electrocardiographical pattern either alone or - more often - together with a typical case history and typical laboratory data.

Supported by a grant from Svenska National- foreningen. mot hjart- och lungsjukdomar, which is gratefully acknowledged.

1 Q7

188

150.

100 I

50 .

J. SIEVEFU AND G. BLOMQVIST

- 1935

Fig. 1. No. of cases by sex and years 1935-1959. - First inf. .... Second inf. --Additional inf.

3. In the absence of typical electrocardio- graphical changes we have accepted cases with a typical clinical case history, typical clinical picture and laboratory data consistent with the diagnosis of myocardial infarction.

The frequency per calendar year during the entire 25 year period in males and females is given in fig. 1. Before the figures for the last five years were available we have in earlier papers discussed the possibility of a rather steep increase in

300

200

100

I a

1933 1945 1959 Fig. 2. No. of cases per year in some Scandinavian materials. --- UllevPl (Oslo, Norway).

------- Ekvall (UmeP, Sweden). ---- Lindtn (Uppsala, Sweden). -- Own material (Malmo, Sweden).

the frequency during the late forties and we have thought that our material gave basis for the assumption that a reasonably steady state was reached in the year 1949. Fig. 1 reveals that this assumption was not too accurate. Apparently a continuous increase has prevailed during the entire 25 year period as to the ab- solute numbers of acute infarctions hos- pitalized.

Fig. 2 is once again a figure from an earlier paper (1) where the last 5 year figures are added. Until the late forties the increase of primary infarctions in our material seems to follow that of the Ullev51-material (8) in Oslo fairly well, whereas after that no information is available for the Oslo material.

The mean sex ratio was 1.66 males versus 1 female in the 20 year material 1935-54 and has shown a slight increase during 1955-59, being on an average

CONTINUED STUDIES ON MYOCARDIAL INFARCTION IN MALMO 189

- 1935 1945 1959

Fig. 3. Sex ratios for the years 1935-1959.

1935 1645 . 1659

Fig. 4. Average age. - Males. -- Females.

2.09 : 1. Fig. 3 gives the sex ratios for the entire 25 year material. The figure for the first year, 1935, is based on very few cases and has to be considered a chance variation. Our figures correspond fairly well with those found in other Scandinavian series where sex ratios be- tween 1.2 : 1 and 2.3 : 1 are found (9, 10, 11, 12, 13, 14, 15).

The mean age for the primary infarc- tion also shows for the last 5 year period good continuity when compared with the earlier 20 year material. As can be seen from fig. 4 there has been, during the entire 25 year period, a continuous in- crease in the mean age as well for males as for females. During the last 5 year

% % 50 50

25 25

I I1 111 IV v I II 111, IV v

Fig. 5. Age adjusted 4 weeks mortality rates. I y 1935-39. I1 1940-44. 111 = 1945-49. IV = 1950-54. V = 1955-59.

period there has been an overall mean age for males of 63.9 with slowly in- creasing tendency. Among the females the overall mean age during the last 5 year period was 69.3. Also here a certain increase per calendar year was noted.

The acute mortality during the hos- pitalization for primary infarctions during 1955-59 was 31.3 % as compared with 35.7 for the previous 20 year material. The corresponding figures for females were 42.6 and 38.1 respectively. Since the acute mortality correlates positively with age at infarction and since the mean age has changed slightly these figures are not quite comparable. In fig. 5 the mortality rates are therefore presented, corrected for the discrepancy as to age composition.

Figures for acute mortality vary con- siderably in the literature, most certainly in many cases due to differences as to composition of the material and com- parisons with other investigations are here even more hazardous than usual. However our figures seem to be of about the same magnitude as those in some

190 J. SIEVERS AND G . BLOMQVIST

Group I1 Medi-

% urn

Table I . Severity groups according to Helander. Frequency distribution in Jiveyear periods

Group No. of I11 patients Mild Yo

Years

79.0 79.5 76.2 75.8 76.8

1935-39 1940-44 1945-49 1950-54 1955-59

1.2 86 5.0 181 5.0 357 4.3 532 4.1 844

Group I Severe YO

10.9 3.9

15

8.0 4.4 4.1

19.8 15.5 18.8 18.9 19.1

0 0 6.5

4 2.0 0

60.1 75.2 42

68.2 76.7 76.8

22.4 23.5 35

27 28.3 22.7

other Scandinavian materials (e. g. 15) while others find higher acute mortality (e. g. 11, 16).

For severity grouping we have been using throughout a classification first put for- ward by Helander (10). The grouping system consists of 3 groups, group I severe cases, group I1 medium cases and group I11 mild cases. For details concerning grouping criteria the reader is referred to Helander’s original paper.

As can be seen from table I we had during the first 20 year period a fairly uniform distribution of our cases in the 3 different groups. In this last 5 year period also this distribution corresponds

fairly well, not to say extremely well, with the previous figures. Thus 19.1 yo was assigned to group I, severe cases, while 76.8 Yo was assigned to group 11, medium cases, and finally 4.1 yo to group 111, mild cases.

We find it important to stress the fact that there has been no substantial change in the severity distribution with calendar year in this investigation. One of the major objections in the literature to the “reality” of the frequency increase of myocardial infarction is that the diagnosis of the condition was not made during earlier years and that the increase found in many countries throughout the civ- ilized world is only a result of more cor- rect diagnoses. In our opinion the pres- ent material gives us reason to believe that this assumption does not hold true for Malmo. If it were so, we would have found an increasing frequency of milder infarctior , during later periods. Table I shows tnat this is by no means the fact.

The percentage of cases in each se- verity group, as well as the mortality within 4 weeks in these groups are given in table 11, together with the correspond- ing figures from some other Swedish materials.

Table II. Severity groups according to Helander. Frequency distribution and mortality in some Swedish materials

Helander (1950) (10) . . . . WAllgren (1950) (12) . . . . LindCn (1952) (13) . . . . . . Helander & Levander (1959) (15) .............. Own material 1935-54 (1 ) Present material 1955-59

I Group I (severe)

% of all cases

-- 29.0 20.9 43

23.8 18.9 19.1

Mortal- ity YO

57 62.5 71

54 79.8 85.7

Group I1 (medium)

yo of all Mortal- cases I ity

Group 111 (mild) No. of patients

193 163 512

286 1,156 844

CONTINUED STUDIES ON MYOCARDIAL INFARCTION IN MALMO

Mean value f S.E.

191

No. of obser- vations

Table III. Transaminase values

202.7 k 42.4 119.3 f 5.3 67.0 & 14.8

~~

Severity group according to Helander

Severe . . . . . . . . . . Medium . . . . . . . . Mild ..........

35 289

15

Another obvious reason for the found increase in exact figures would be the increase of the population in Malmo. In an earlier paper (1) we have presented a figure giving the increase for males and females both in separate age groups and with all age groups taken together. The figures were given as cases of myo- cardial infarction per 1,000 inhabitants in corresponding age groups. Fig. 6 pre- sents the same picture with the curves extended for the last 5 year period. Ap- parently the increase prevails even when the age composition and the increase in total number of inhabitants in Malmo is taken into consideration.

The glutarnic-oxalacetic transarninase (GOT) in cases of myocardial infarc- tion has been studied by a large number of investigators, among others by Hanson and Biorck at this Department (17, 18). For detailed literature references in this connection the reader is referred to the extensive literature survey by Wr6blewski

In the present material the GOT in serum was determined in 36.7 yo of the material on the second, third (or both) day after clinical onset. In table I11 the mean values and the standard errors are given for the 3 severity groups. A statistically significant correlation ap- pears between the GOT mean values and the severity, as judged by the Helander grouping criteria. This was to be ex- 13-623003. Acta M e d . Scand. Vol. 172.

(19).

%. 9

1/ 5 3 // 1 MALES / /

1 :I 3 5

&. ,

'T 1935-39 40-44 45-49 50-54 55-59

Fig. 6. No. of hospitalized cases of myocardial infarction per 1,000 inhabitants by sex and age groups, Malmo 1935-1959. 1 ) Males 30-49. 5) Females 30-49. 2) D 50-69. 6) )> 5&-69. 3) D > 69. 7) >> :> 69. 4) B total. 8) D total.

pected, since a correlation between the extent of the infarction and the GOT- levels has been shown by a number of investigators.

Finally some figures concerning the frequency of myocardial rupture might be of interest.

The total number of deaths 1955-59 was 373 (224 males and 149 females). 94.2 yo of the males and 89.9 yo of the females were autopsied, which gives a total autopsy rate of 92.5 yo.

Thirty-five ruptures were observed in 345 autopsies, giving a rupture frequency of 10.1 yo. In table IV the percentage of ruptures in different age groups for males and females is given.

192 J. SIEVERS AND G . BLOMQVIST

Age

In our previous 20 year material the overall frequency of rupture was slight- ly higher, 13.0 yo. The increasing fre- quency with age, obvious in the present material, was also noted in our previous series and is well in agreement with the fiildings of other investigators (e. g. 20).

A higher incidence of rupture among females than among males is reported previously. This is also the fact in the present material, the age adjusted sex difference being highly significant (p =

0.001). No definite explanation to this difference is agreed upon in the liter- ature, though some suggestions as to the mechanism have been put forward (e. g. 20).

Males Females

Ruptures No. of au- Ruptures 70 topsies 70

Summary As a complement to a previously re-

ported 20 year material of 1,821 hos- pitalized cases of myocardial infarction the following 5 year period of 1955-59 is reviewed and an additional material of 1,067 cases is presented, bringing our total 25 year material to a number of 2,888 cases.

The present paper is a preliminery report only giving figures on a selectcd number of items. A more extensive study of the material is under preparation.

The continuous increase with calendar y e a , both in absolute figures and cor-

I Total

No. of au- 1 Ruptures topsies ~ yo topsies

No. of au-

51 1 ::: 1 12:

134 1 10.1 1 345

80 12.2 164 - 33.3 3

related to a well defined base population, is presented and the distribution within severity groups during different time periods is discussed.

The sex ratio is found to be 2.09 males to 1 female.

The mean age is slowly increasing during the entire 25 year period and the figure for males 1955-59 is 63.9, for females 69.3.

The acute mortality is 31.3 yo in the present material, compared with 35.7 in the preceding 20 year series.

Figures on the glutamic-oxaloacetic transaminase content of serum are pre- sented and the positive correlation be- tween these and the severity of the in- farction, as judged clinically, is demon- strated.

Finally figures are given on myocardial rupture. A frequency of 10.1 yo is found in our autopsy material. The earlier known increase with age is demonstrated as is the statistically higher rupture fre- quency among females than among males.

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CONTINUED STUDIES ON MYOCARDIAL INFARCTION IN MALMO 193

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