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Hospital registration in patients with acute myocardial infarction
Hospital acute
registration myocardial
in
patients
infarction
Graeme Sloman, M.B., B.Sc., F.R.C.P.(Edin.)., F.A.C.C.* Roger Brown, M.B., B.S., M.R.A.C.P. Victoria, Australia
I
n the last six years, a considerable amount of information has accumulated from the study of patients with acute myocardial infarction in coronary care units. This information has been well reviewed in a Rand Corporation Publication (Rockwelllo). At the present time, there is very little known about the outcome of all patients presenting at a hospital with a provisional diagnosis of a “heart attack.” Some information has been provided in a retrospective study by Cross,’ however, prospective information would be more valuable in viewing the problem in perspective. We here present a review of all patients admitted to the Royal Melbourne Hospital during a six-month period with a provisional diagnosis of acute myocardial infarction, as well as those patients who, while in hospital, were shown to have a recent myocardial infarction. Methods
and
with
materials
Since March 1, 1968, a register has been kept of all patients admitted to the Royal Melbourne Hospital with a provisional diagnosis of acute myocardial infarction.
F.R.A.C.P.,
M.R.C.P.(Lond.),
In order to obtain a near complete cover of all patients, the hospital and autopsy records were also searched, electrocardiograms were reviewed, and a personal liaison was established with the medical wards in an attempt to obtain complete registration of all patients with definite or suspect acute myocardial infarction. Each registered patient was seen by one of us and a special pro forma designed for the study was completed. The reviewer took no part in the management of the patients but saw the patients on two or three occasions during the hospital stay to confirm the clinical observations and to obtain standardization in the reports on chest x-rays and electrocardiograms (ECG’s). The Minnesota Code” was used for reporting the ECG’s. Electrocardiograms with Q and Q-S changes coded as l:l, 1:2, 1:3, together with sequential S-T and T-wave changes (9-2) were recorded as having unequivocal electrocardiographic evidence of infarction. T-wave changes alone (5-1 to 5-4) were regarded as equivocal electrocardiographic evidence of acute myocardial infarction. Enzyme levels of serum glutamic oxalacetic transaminase greater than
From the Cardiac Department. The Royal Melbourne Hospital, Victoria. Australia. Received for publication July 22. 1969. Reprint requests to: Dr. Sloman, Cardiac Department. The Royal Melbourne Hospital, 3050 Victoria, Australia. *Supported in part by a grant from the National Heart Foundation of Australia. No. C524/428, and agrant from the United States Public Health Service.
1701. 79,
NO. 6, pp. 761-768
June,
1970
American Heart Journal
761
762
Slomtr
I1 11 rtd
lrlli~r-. llcarl .I. .~1rrtc, 1970
13rowtr
40 units, serum lactic dehydrogenase greater than 250 units, and creatine phosphokinase activity levels greater than 70 units were regarded as positive levels. By considering the history, ECG, and enzyme studies, the patients were classified into one of the following six diagnostic groups according to World Health Organization classification : Class 1. Dejinite acute myocardiul infurction. This group includes patients with: (a) unequivocal ECG evidence of recent infarction (sequential changes of injury current, or the observed development of abnormal Q waves) with or without a typical history; (b) equivocal ECG evidence of recent infarction with abnormally high level(s) of the appropriate serum enzyme(s) with or without a typical history; (c) normal ECG with abnormally high level(s) of appropriate serum enzyme(s) and a typical history; (d) postmortem evidence of acute myocardial infarction. Class 2. Probable acute myocardiul infarction. This group comprises cases with a typical history but with equivocal ECG evidence of recent infarction and equivocal elevation of serum enzyme level(s). Class 3. Possible ncute myocardial infarction. This class comprises cases with a typical history but either equivocal or no ECG changes of infarction and with no elevation of serum enzyme level(s). Class 4. Atypical cases.The patients in this class have histories which were atypical and there were no significant abnormalities of the ECG or serum enzyme level(s). Class 5. No acute myocardial infarction. In this class, another definite diagnosis was made. Class6. Insuficient data. This group comprises cases with insufficient items of evidence to allocate to the categories 1,2,3, or 4, but where no other diagnosis was positively made. No attempt was made to classify the infarction on the basis of severity, but the following clinical features noted on admission were recorded. Pulse rate and rhythnl, blood pressure, presence of peripheral vasoconstriction, cyanosis, degree of consciousness, cardiac enlargement, added heart sounds, pulmonary crepitations, elevation of systemic venous pressure, edema, peri-
cardial friction rub, and/or cardiac bruits. Cardiogenic shock was diagnosed when the systolic blood pressure was below 90 mm. Hg and there was evidence of “shock” as manifest by peripheral vasoconstriction and oliguria. The coronary care unit at the hospital consisted of a two-bed ward with ECG monitoring and continuous nursing observation. Patients were admitted to the unit on a bed-available basis or referred because of some severe complication of myocardial infarction. Results
In the six months under review, 278 patients were registered. Of these, 79 (28.4 per cent) were treated in the coronary care unit. The over-all incidence, sex, and mortality rate in each World Health Organization class is shown in Table I. Of the total of 27% patients, 96 (34.5 per cent) were females and 182 were male, but females constituted only 17.7 per cent of the coronary care unit groups. The 222 patients (80 per cent of the groups) who were classified into Class 1 (definite acute myocardial infarction) had a hospital mortality rate of 24.3 per cent. There were 6, 18, 12, 10, and 10 patients in Classes2 to 6, respectively. The 10 patients admitted with a provisional diagnosis of acute myocardial infarction who were later found to have another definite diagnosis (Class 5) had the following conditions: pulmonary embolism, cholelithiasis, abdominal pain with epilepsy, thyrotoxic cardiomyopathy, chest infection, pericarditis, and acute pulmonary edema without identified cause, and two had influenza. The only death in this group occurred in the remaining patient, a woman with a dissecting aortic aneurysm. The ten patients in Class 6 were all admitted moribund and died soon after. No clinical diagnosis was made, investigations were not begun, and autopsy was not performed in any case. It was considered that the majority of these had nevertheless suffered an acute myoc-ardial infarction, however, this could no1 l)e confirmed. ‘I‘he incidence and mortality of the 2.58 patients in Classes 1 to 4 as related to age are shown in Table II. The mean age of all
Volume
73
Number
6
reyistmtion
Hospital
Table 1. Sex, incidence, und mortulity
Hosfiital
Class I (Definite)
or C.C. U.
Hospital Males Females (Mortality Total Deaths (Mortality
of myocurdial
rate of each of the W.H.O.
Class 2 (Probable)
Class 3 (Possible)
Class 4 (At#kal)
infarction
patients
groups Class 5 (No. A.M.I.)
Class 6 (I?m@cient data)
Total
90 60
3 2
13 4
4 7
3 4
4 5
117
150
5
17
11
7
9
(MY&) 199
(loo!%)
(26.?%)
1 0 1
65
rate)
rate)
763
(24.:;)
(35;)
c.c.u. Males Females Total (Mortality
rate)
Deaths (Mortality
rate)
Total (Hospital Males (Mortality Females (Mortality Total Deaths (Mortality
C.C.U.
(23.&)
rate)
(lOA)
2 1 3
(17.!%)
(2Z%)
(33;;)
149
4
14
5
5
5
182
73
2
4
7
5
5
222
6
18
12
10
10
(65t?) (34.5%) 278
(24?%)
(16.!6%)
(26.y%)
(39k)
care unit.
or C.C. U.
rate
in Classes 1 to 4 grouped by age / 30-39
yr.
1 40-49
yr.
1 50-59
yr.
and
area
/ 60-69
yr.
in which treated 1 70-79
yr.
1 80-89
(%)
1.5 1 6.6
26 4 15.4
27 10 37
4 1 25
0 0 0
75 18 24
6 2 33
38 1 2.6
65 8 12.3
a9 29 32.6
51 21 41
9 1 11.1
258 62 24
14
25
37
19
3
100
39.4
40
30
8
0
29
care unit.
62 19 30.6
47 20 42.5
9 1 11.1
Total
3 2 66
50
39 4 10.3
1
(%)
2
23 0 0
yr.
3 0 0
Total (Hospital and C.C. U.) Deaths Mortality rate (%) Per cent of total no. of patients Per cent of group in C.C.U. = Coronary
1 0 1
rate
Hospital group Total Deaths Mortality rate
C.C.U.
1 0 1
rate)
Table II. Patients
C. C. U. group Total Deaths Mortality
1 0 1
and C. C, U.)
= Coronary
Hospital
59 13 72
383 44 24
764
Slomun
und Brows
patients in Classes 1 to 4 was 61.1 years, while that of the 75 patients admitted to the coronary care unit was 56.2 years. Table II shows that a greater proportion of the younger patients was treated in the coronary care unit. If we exclude the first and last age grouping, where the numbers are small, it can be seen that there is a rising mortality rate with age from a low of 2.6 per cent in the 40 to 49 age groups to a high of 41 per cent in the 70 to 79 age groups. The highest mortality rate in the coronary care unit patients (37 per cent) was in the age group 60 to 69 years, while the hospital ward patients registered their highest in the next older decade (42.5 per cent). Table III compares the sex incidence and the age. Although female patients constituted roughly one third of the total, they made up a greater proportion of the older
age groups, 70 to 79 years and 80 to 89 years. Their hospital mortality rate, 33.3 per cent, was higher than the mortality rate of the male groups (19.3 per cent). If one looks at the mortality under and over 60 years of age, we find 6 of 29 females under the age of 60 dying (20 per cent) while 5 of 80 males died (6.0 per cent). The male mortality is noticeably different (p > 0.1). Over 60 years, 28 of 91 males died (31 per cent) while 23 of 58 females died (40 per cent). In this situation there was no statistical difference between the two groups (p > 0.70). The period between the onset of infarction and the time of admission to hospital is shown in Table IV. (Three per cent of the infarctions occurred in hospital and the majority of these were associated with acute surgical blood loss.) Ninety-eight patients (38 per cent) were admitted to hospital
Table III. Age of registration related to sex trnd hospital mortality rate
Age groufis
1 30-39
1 40-49
/
SO-59
1
60-69
1
70-79
1
80-89
1
Total
/ ZC?$~
Females Males Per cent of group being female Deaths: Female (Mortality rate) Deaths: Male (Mortality rate)
Table IV. Outcome in patients admitted within six hours of the onset of severepain (Classesl--f) Hospifal or C.C. U. / O-l hr. 1 Hospital Deaths rate)
C.C.U.
/ 2-3 hr.
3
3
9
0 wz)
1 (33%)
1 (1lYd
4
8
)
3-4 hr. 17
/
4-5 hr. 10
/ 5-6 hr. 17
1
Total 59 (60%)
(Mortality
C.C.u. Deaths rate) Total Deaths rate)
l-2 hr.
10
1
W%,)
7
0 (0%)
2 (12%)
6
4
5 (8.80/b) 39 (40%)
(Mortality 1 (25%) 7
1 (12.5%) 11
1 (14%)
2 WV3
(Mortality
= Coronary
care unit.
4 (40%) 19
5 (26%)
1 (14.3%) 24 2 (8.3%)
2 (25%) 16
2 (12.5%)
1 (25%) 21
3 (14%)
10W.60/,) 98
15 (15Yo)
Hospital
registration
within six hours of the onset of infarction. Forty per cent of these patients were admitted to the coronary care unit, while 60 per cent were admitted to general hospital beds. While the over-all mortality rate of this group was 15 per cent, there was a much higher relative mortality rate in the patients admitted to the coronary care unit. In the coronary care unit, there were 10 deaths, giving a mortality of 25.6 per cent, while of the hospital patients, there were only 5 deaths giving a mortality rate of 8.8 per cent. The mortality rate for the 160 patients admitted to hospital more than 6 hours after the onset of infarction was 30 per cent and this was significantly greater (p > 0.025) than the mortality rate of those patients admitted to hospital under 6 hours. The average age of the patients admitted within 6 hours of the onset of severe pain was 55.5 years in the coronary care unit and 60.6 years in the ward beds. The mean age of the ten patients who died in the coronary care unit was 57.8 years, while the mean age of the 5 patients who died in ward beds was 64.2 years. Table V details the clinical state of the patients at the time of their first examination after admission to hospital. The 258 patients are divided into the coronary care
of myocardial
infarction
patients
765
group and the hospital group and it can be seen that all the deaths in the coronary care unit were in patients who had persistent lung crepitations at the time of their first examination and in those patients with cardiogenic shock. In the hospital group, 4 patients in whom there was no evidence of shock, crepitations, or elevation of the venous pressure, died, while one patient who had only elevation of the venous pressure succumbed. The other patients who died in the hospital group were those with evidence of persistent crepitations at the lung bases on admission or in those in whom cardiogenic shock occurred. Thus, the mortality rate for the hospital group, excluding patients with “cardiogenie shock,” is 17 per cent (27 of 163 patients), whereas for the similar coronary care unit group, the mortality rate is 14 per cent (8 of 59 patients). In a previous report from the same hospital,12 there was an 18 per cent mortality rate in patients treated in the coronary care unit and a 29.8 per cent mortality rate in patients treated in the general wards of the hospital when patients in cardiogenic shock were excluded. Discussion
In previous reports from the Royal Melbourne Hospital we have described the
Table V. Clinical severity in Classes1 to 4 determined at time of admission
Hosfdal
07
CC. U.
No shock, crefiitations, or elewalion of venous pressure
Persistent lung crepitations
Elevation of venous
Cardiogenic shock
Total
$wessure
Per cent of group Deaths Mortality rate (y,)
28 4 8
107 60 22 20.6
5 3 1 20
20 12 17 85
c. c. u. Per cent of group Deaths Mortality rate (%)
21 28 0 0
36 48 8 17
2 3 0 0
16 21 10 62.5
7.5
72
143
7
36
2.58
285 4
5.5 21 30
14 3 1
:t 27
24 62
Hos&taL
51
and C.C. LJ.) group Mortality Per cent ofrate (%) Deaths
Total
C.C.U.
(Hospital
= Coronary
care unit.
183 44 24
18 24
establishment of the coronary care unit.7~‘” There is little doubt that the recognition of cardiac arrhythmias at an early stage following acute infarction leads to more efficient treatment of patients with acute myocardial infarction. It is in this area of treating arrhythmias rapidly and efficiently that the coronary care unit has most clearly shown its effectiveness.395 Longterm survival following resuscitation from cardiac arrest occurring both in the coronary care unit and in ward beds attest to this improvement in medical management.8~gJ3 While it is recognized that acute myocardial infarction is the main cause of premature death in the population of the developed countries, there is very little accurate information about the clinical course of the condition in patients whether they are managed inside a hospital or in the home. In this paper we have reported some of the information gained from registering all persons admitted to the hospital with a provisional diagnosis of acute infarction together with those patients found in the hospital to have suffered a myocardial infarction. The patients registered were managed either in general ward beds or in a two-bed coronary care unit. We have analyzed certain characteristics of these two groups of patients separately and, in so doing, the differences between the groups have been highlighted. In emphasizing the difference between the patients, it was noted that the coronary care unit received fewer female patients and that the average age of the patients admitted to the coronary care unit was significantly less than the age of the patients in the hospital ward beds. While one would not wish to put an age limit on admission to a coronary care unit, it seems not unreasonable to admit the younger patients to the unit. Twenty-one per cent of the patients admitted to the coronary care unit had “cardiogenic shock” on admission compared with “cardiogenic shock” recorded in only 12 per cent of the patients admitted directly to a ward bed. These figures support the general concept that in many hospitals with a coronary care unit, the policy is to admit the more seriously ill patients to the spe-
cialized unit, these tending to “swamp” the unit with seriously ill patients who may not obtain great benefit from special care. In this review, the mortality rate in the “shocked” patients admitted to the hospital ward bed was higher than that among the patients admitted to the coronary care unit. This reflects some advantage in admitting the “shock” patient to the coronary care unit. However, the greatest value of the specialized coronary care unit relates to the treatment of the patients with acute infarction and cardiac arrhythmias and this value may be minimized by the unit receiving a very high proportion of patients with cardiogenic shock who only benefit to a small degree from the specialized treatment available in the coronary care unit. While it is beyond the scope of this report to make an objective assessment of the effectiveness of the coronary care unit in a hospital, it is considered that the maintenance of a register of patients coming into the hospital with acute manifestations of coronary artery disease will, in due course, make it possible to characterize those patients who will benefit most from being admitted to a specialized coronary care unit. This information will be of considerable value to those hospitals who are only able to maintain a small coronary care unit where a decision has to be made as to which type of patients should be admitted to the special unit. Accepting at this time that most clinical and statistical evidence supports the contention that the coronary care unit provides an area in which a patient with acute infarction can be given more effective treatment, then we have to decide on the value of admitting all patients with acute infarction to such a unit. In our series of 278 patients registered in the six-month period, 258 were allocated in Classes 1 to 4 and would definitely qualify for admission to a coronary care unit. The additional 20 patients who were registered in Classes 5 to 6 would also qualify for admission once diagnosed. This makes an estimated total of 556 patients in one year. Assuming a relatively even distribution of admission over the 12 months, the hospital would require a five-bed unit to keep each patient in the unit three days after admission.
Vaiume Number
73 6
No.ofA.M.1.
Hospital
registration
X averageno. ofdaysinunit 365
)
Due to the uneven distribution of patients, however, the unit would probably require an increment in beds of 25 per cent to cover the peaks of admissions. In patients over the age of 60 years, there was no difference between the mortality rates of the two sexes. In patients under the age of 60 years, there was, however, a noticeable difference in the mortality rate between the sexes with a significantly higher mortality rate in female patients. When a female under 60 years of age suffers an acute myocardial infarction, there is more severe involvement with a greater risk of death. The time of admission to the hospital following infarction had a noticeable effect on the hospital mortality rate. The patients admitted to hospital within six hours had a lower mortality rate than those admitted after six hours. This difference may be due to patients being admitted early (under six hours) because they had suffered an acute infarction and their medical advisor considered that they should be in the hospital, while those patients admitted after six hours were referred because they had suffered a complication of acute myocardial infarction. It is interesting to note that there was a higher hospital mortality rate among those patients admitted to the coronary care unit within six hours of the onset of their severe pain. This observation reflects the tendency to admit the more seriously ill, younger patient to the coronary care unit, particularly in the early stages after an acute myocardial infarction. Review of the initial clinical presentation related to hospital mortality rate (Table V) shows that the patient with evidence of cardiac decompensation on admission to hospital has less chance of survival. This relationship was evident irrespective of whether the patient was admitted to a hospital ward bed or to the coronary care unit. The register highlights the need for improved treatment of heart failure in all patients. It is interesting to note that when one excludes patients with cardiogenic shock, there does appear to be a reduction in mortality rate in patients treated in -:
of myocardial
infarction
patients
767
hospital wards from 29.8 per cenP to 18 per cent in the present report. While the method of identification of patients differed in the earlier report, the mortality reduction suggests improvement in the management of patients with acute infarction, not only in the coronary care unit, but also in the general hospital wards. Registration may make it possible to detect, within a hospital population, the form of treatment which will produce an alteration in survival. The data obtained from the registration of patients will help to provide a background of knowledge on which a rational plan of adequate hospital service can be provided. The establishment of coronary care units has given a suitable stimulus to the attempt to improve the management of patients with acute myocardial infarction. Initial published reports from the units emphasized the value of the new concept, however, it is now timely to examine the entire problem of the management of all patients presenting to the hospital with acute manifestations of coronary artery disease. Since the first units were established in 1962,2v6there have been important changes in the management of acute myocardial infarction with the introduction and wider use of drugs such as procainamide, propranolol, and lidocaine for the treatment of cardiac arrhythmias. The development of more potent diuretic drugs and the more rational use of digitalis in the management of cardiac decompensation has also evolved. With the availability of these drugs, there has been a widespread change in emphasis from the treatment of cardiac arrest to its prevention by the earlier and more aggressive management of arrhythmias4 coupled with the more enthusiastic treatment of patients with mild heart failure. It is against this background of changing therapy that the effectiveness of treatment of acute myocardial infarction should be assessed.It is considered that registration of patients within the hospital will indicate the areas where treatment still falls short and where it may be improved. Summary
Registration of 278 patients admitted to the Royal Melbourne Hospital during
768
Slomun und Brown
a six-month period with definite or suspected acute myocardial infarction has been achieved. One hundred and ninety-nine patients were admitted to general ward beds, while 79 patients were admitted to a two-bed coronary care unit. For the purpose of analysis, registered patients were placed in one of the six diagnostic classes recommended by the World Health Organization. A comparison of the patients admitted to hospital ward beds and to the coronary care unit emphasized the basic difference in the two groups of patients. The coronary care unit patients were younger, they had a higher incidence of cardiogenic shock on admission, and there was a higher mortality rate among those patients admitted to the unit within six hours of the onset of their severe pain. The over-all hospital mortality rate was 24 per cent in the patients admitted to the ward beds and to the coronary care unit. The register provides a background of information on which the effectiveness of the management of patients with acute myocardial infarction can be assessed. We thank the Medical Staff of the Royal Melbourne Hospital for permission to study patients in their care. We thank Miss Janice Ferguson who was responsible for the initial registration of all patients. We also thank Dr. E. B. Cross and Dr. Ted Cooper of the United States Public Health Service for their continued support of the project.
2. 3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
REFERENCES 1.
Cross, E. B.: in Julian, D. G., and Oliver, Acute myocardial infarction, Edinburgh, E. & S. Livingstone, Ltd.
M. F.: 1968,
14.
ljaq, 1~1.: Preliminary studies in the acute coronary care area, J. Lancet 83:53, 1963. Lawrie, D. N., Higgins, N. Ii., Godman. M. J., Oliver, N. F., Julian, D. G., and Donald, K. W.: Ventricular fibrillation complicating acute myocardial infarction, Lancet 2:523, 1968. Lawn, B., Fakhro, A. M., Hood, W. B., Jr., and Thorn, G. W.: The coronary care unit: New perspective and directions, J. A. M. A. 199:188, 1967. Lown, B., and Vassaux, C.: Lidocaine in acute myocardial infarction, AMER. HEART J. 76586, 1968. Meltzer, L. E.: Coronary units can help decrease hospital deaths, Mod. Hosp. 104:102, 1965. Robinson, J. S., Sloman, G., and McRae, C.: Continuous electrocardiographic monitoring in the eariv stages after acute myocardial infarction, Med. Jr Aust. 1:427, 1967. Robinson. 1. S.. Sloman. G.. Mathew. T. H.. and Gable, A. J.: Survival after resuscitation from cardiac arrest after myocardial infarction, AMER. HEART J. 69:740, 1965. Robinson. I. S.. and Sloman. G.: Resuscitation from cardiac arrest after myocardial infarction, Med. J. Aust. 1:578, 1965. Rockwell, M. A.: A summary of medical literature describing the effectiveness of coronary care units. RM-5944-Rand CorDoration. 1969. Rose, G. A., and Blackburn, H. : ‘Cardiov&cular survey methods, World Health Organization Monograph Series No. 56, 1968. Sloman, G., Stannard, M., and Goble, A. J.: Coronary care unit-A review of 300 patients monitored since 1963, AMER. HEART J. 75:140, 1968. Stannard, Mary, and Sloman G.: Ventricular fibrillation in acute myocardial infarction: Prognosis following successful resuscitation, AMER. HEART J. ‘X:573, 1969. W.H.O. Euro .5010(l), 1968: Ischaemic heart disease registers, Report by a Working Party, Copenhagen, 1968. I”
,”
,
.
,
I
registration myocardial
in
patients
infarction
Graeme Sloman, M.B., B.Sc., F.R.C.P.(Edin.)., F.A.C.C.* Roger Brown, M.B., B.S., M.R.A.C.P. Victoria, Australia
I
n the last six years, a considerable amount of information has accumulated from the study of patients with acute myocardial infarction in coronary care units. This information has been well reviewed in a Rand Corporation Publication (Rockwelllo). At the present time, there is very little known about the outcome of all patients presenting at a hospital with a provisional diagnosis of a “heart attack.” Some information has been provided in a retrospective study by Cross,’ however, prospective information would be more valuable in viewing the problem in perspective. We here present a review of all patients admitted to the Royal Melbourne Hospital during a six-month period with a provisional diagnosis of acute myocardial infarction, as well as those patients who, while in hospital, were shown to have a recent myocardial infarction. Methods
and
with
materials
Since March 1, 1968, a register has been kept of all patients admitted to the Royal Melbourne Hospital with a provisional diagnosis of acute myocardial infarction.
F.R.A.C.P.,
M.R.C.P.(Lond.),
In order to obtain a near complete cover of all patients, the hospital and autopsy records were also searched, electrocardiograms were reviewed, and a personal liaison was established with the medical wards in an attempt to obtain complete registration of all patients with definite or suspect acute myocardial infarction. Each registered patient was seen by one of us and a special pro forma designed for the study was completed. The reviewer took no part in the management of the patients but saw the patients on two or three occasions during the hospital stay to confirm the clinical observations and to obtain standardization in the reports on chest x-rays and electrocardiograms (ECG’s). The Minnesota Code” was used for reporting the ECG’s. Electrocardiograms with Q and Q-S changes coded as l:l, 1:2, 1:3, together with sequential S-T and T-wave changes (9-2) were recorded as having unequivocal electrocardiographic evidence of infarction. T-wave changes alone (5-1 to 5-4) were regarded as equivocal electrocardiographic evidence of acute myocardial infarction. Enzyme levels of serum glutamic oxalacetic transaminase greater than
From the Cardiac Department. The Royal Melbourne Hospital, Victoria. Australia. Received for publication July 22. 1969. Reprint requests to: Dr. Sloman, Cardiac Department. The Royal Melbourne Hospital, 3050 Victoria, Australia. *Supported in part by a grant from the National Heart Foundation of Australia. No. C524/428, and agrant from the United States Public Health Service.
1701. 79,
NO. 6, pp. 761-768
June,
1970
American Heart Journal
761
762
Slomtr
I1 11 rtd
lrlli~r-. llcarl .I. .~1rrtc, 1970
13rowtr
40 units, serum lactic dehydrogenase greater than 250 units, and creatine phosphokinase activity levels greater than 70 units were regarded as positive levels. By considering the history, ECG, and enzyme studies, the patients were classified into one of the following six diagnostic groups according to World Health Organization classification : Class 1. Dejinite acute myocardiul infurction. This group includes patients with: (a) unequivocal ECG evidence of recent infarction (sequential changes of injury current, or the observed development of abnormal Q waves) with or without a typical history; (b) equivocal ECG evidence of recent infarction with abnormally high level(s) of the appropriate serum enzyme(s) with or without a typical history; (c) normal ECG with abnormally high level(s) of appropriate serum enzyme(s) and a typical history; (d) postmortem evidence of acute myocardial infarction. Class 2. Probable acute myocardiul infarction. This group comprises cases with a typical history but with equivocal ECG evidence of recent infarction and equivocal elevation of serum enzyme level(s). Class 3. Possible ncute myocardial infarction. This class comprises cases with a typical history but either equivocal or no ECG changes of infarction and with no elevation of serum enzyme level(s). Class 4. Atypical cases.The patients in this class have histories which were atypical and there were no significant abnormalities of the ECG or serum enzyme level(s). Class 5. No acute myocardial infarction. In this class, another definite diagnosis was made. Class6. Insuficient data. This group comprises cases with insufficient items of evidence to allocate to the categories 1,2,3, or 4, but where no other diagnosis was positively made. No attempt was made to classify the infarction on the basis of severity, but the following clinical features noted on admission were recorded. Pulse rate and rhythnl, blood pressure, presence of peripheral vasoconstriction, cyanosis, degree of consciousness, cardiac enlargement, added heart sounds, pulmonary crepitations, elevation of systemic venous pressure, edema, peri-
cardial friction rub, and/or cardiac bruits. Cardiogenic shock was diagnosed when the systolic blood pressure was below 90 mm. Hg and there was evidence of “shock” as manifest by peripheral vasoconstriction and oliguria. The coronary care unit at the hospital consisted of a two-bed ward with ECG monitoring and continuous nursing observation. Patients were admitted to the unit on a bed-available basis or referred because of some severe complication of myocardial infarction. Results
In the six months under review, 278 patients were registered. Of these, 79 (28.4 per cent) were treated in the coronary care unit. The over-all incidence, sex, and mortality rate in each World Health Organization class is shown in Table I. Of the total of 27% patients, 96 (34.5 per cent) were females and 182 were male, but females constituted only 17.7 per cent of the coronary care unit groups. The 222 patients (80 per cent of the groups) who were classified into Class 1 (definite acute myocardial infarction) had a hospital mortality rate of 24.3 per cent. There were 6, 18, 12, 10, and 10 patients in Classes2 to 6, respectively. The 10 patients admitted with a provisional diagnosis of acute myocardial infarction who were later found to have another definite diagnosis (Class 5) had the following conditions: pulmonary embolism, cholelithiasis, abdominal pain with epilepsy, thyrotoxic cardiomyopathy, chest infection, pericarditis, and acute pulmonary edema without identified cause, and two had influenza. The only death in this group occurred in the remaining patient, a woman with a dissecting aortic aneurysm. The ten patients in Class 6 were all admitted moribund and died soon after. No clinical diagnosis was made, investigations were not begun, and autopsy was not performed in any case. It was considered that the majority of these had nevertheless suffered an acute myoc-ardial infarction, however, this could no1 l)e confirmed. ‘I‘he incidence and mortality of the 2.58 patients in Classes 1 to 4 as related to age are shown in Table II. The mean age of all
Volume
73
Number
6
reyistmtion
Hospital
Table 1. Sex, incidence, und mortulity
Hosfiital
Class I (Definite)
or C.C. U.
Hospital Males Females (Mortality Total Deaths (Mortality
of myocurdial
rate of each of the W.H.O.
Class 2 (Probable)
Class 3 (Possible)
Class 4 (At#kal)
infarction
patients
groups Class 5 (No. A.M.I.)
Class 6 (I?m@cient data)
Total
90 60
3 2
13 4
4 7
3 4
4 5
117
150
5
17
11
7
9
(MY&) 199
(loo!%)
(26.?%)
1 0 1
65
rate)
rate)
763
(24.:;)
(35;)
c.c.u. Males Females Total (Mortality
rate)
Deaths (Mortality
rate)
Total (Hospital Males (Mortality Females (Mortality Total Deaths (Mortality
C.C.U.
(23.&)
rate)
(lOA)
2 1 3
(17.!%)
(2Z%)
(33;;)
149
4
14
5
5
5
182
73
2
4
7
5
5
222
6
18
12
10
10
(65t?) (34.5%) 278
(24?%)
(16.!6%)
(26.y%)
(39k)
care unit.
or C.C. U.
rate
in Classes 1 to 4 grouped by age / 30-39
yr.
1 40-49
yr.
1 50-59
yr.
and
area
/ 60-69
yr.
in which treated 1 70-79
yr.
1 80-89
(%)
1.5 1 6.6
26 4 15.4
27 10 37
4 1 25
0 0 0
75 18 24
6 2 33
38 1 2.6
65 8 12.3
a9 29 32.6
51 21 41
9 1 11.1
258 62 24
14
25
37
19
3
100
39.4
40
30
8
0
29
care unit.
62 19 30.6
47 20 42.5
9 1 11.1
Total
3 2 66
50
39 4 10.3
1
(%)
2
23 0 0
yr.
3 0 0
Total (Hospital and C.C. U.) Deaths Mortality rate (%) Per cent of total no. of patients Per cent of group in C.C.U. = Coronary
1 0 1
rate
Hospital group Total Deaths Mortality rate
C.C.U.
1 0 1
rate)
Table II. Patients
C. C. U. group Total Deaths Mortality
1 0 1
and C. C, U.)
= Coronary
Hospital
59 13 72
383 44 24
764
Slomun
und Brows
patients in Classes 1 to 4 was 61.1 years, while that of the 75 patients admitted to the coronary care unit was 56.2 years. Table II shows that a greater proportion of the younger patients was treated in the coronary care unit. If we exclude the first and last age grouping, where the numbers are small, it can be seen that there is a rising mortality rate with age from a low of 2.6 per cent in the 40 to 49 age groups to a high of 41 per cent in the 70 to 79 age groups. The highest mortality rate in the coronary care unit patients (37 per cent) was in the age group 60 to 69 years, while the hospital ward patients registered their highest in the next older decade (42.5 per cent). Table III compares the sex incidence and the age. Although female patients constituted roughly one third of the total, they made up a greater proportion of the older
age groups, 70 to 79 years and 80 to 89 years. Their hospital mortality rate, 33.3 per cent, was higher than the mortality rate of the male groups (19.3 per cent). If one looks at the mortality under and over 60 years of age, we find 6 of 29 females under the age of 60 dying (20 per cent) while 5 of 80 males died (6.0 per cent). The male mortality is noticeably different (p > 0.1). Over 60 years, 28 of 91 males died (31 per cent) while 23 of 58 females died (40 per cent). In this situation there was no statistical difference between the two groups (p > 0.70). The period between the onset of infarction and the time of admission to hospital is shown in Table IV. (Three per cent of the infarctions occurred in hospital and the majority of these were associated with acute surgical blood loss.) Ninety-eight patients (38 per cent) were admitted to hospital
Table III. Age of registration related to sex trnd hospital mortality rate
Age groufis
1 30-39
1 40-49
/
SO-59
1
60-69
1
70-79
1
80-89
1
Total
/ ZC?$~
Females Males Per cent of group being female Deaths: Female (Mortality rate) Deaths: Male (Mortality rate)
Table IV. Outcome in patients admitted within six hours of the onset of severepain (Classesl--f) Hospifal or C.C. U. / O-l hr. 1 Hospital Deaths rate)
C.C.U.
/ 2-3 hr.
3
3
9
0 wz)
1 (33%)
1 (1lYd
4
8
)
3-4 hr. 17
/
4-5 hr. 10
/ 5-6 hr. 17
1
Total 59 (60%)
(Mortality
C.C.u. Deaths rate) Total Deaths rate)
l-2 hr.
10
1
W%,)
7
0 (0%)
2 (12%)
6
4
5 (8.80/b) 39 (40%)
(Mortality 1 (25%) 7
1 (12.5%) 11
1 (14%)
2 WV3
(Mortality
= Coronary
care unit.
4 (40%) 19
5 (26%)
1 (14.3%) 24 2 (8.3%)
2 (25%) 16
2 (12.5%)
1 (25%) 21
3 (14%)
10W.60/,) 98
15 (15Yo)
Hospital
registration
within six hours of the onset of infarction. Forty per cent of these patients were admitted to the coronary care unit, while 60 per cent were admitted to general hospital beds. While the over-all mortality rate of this group was 15 per cent, there was a much higher relative mortality rate in the patients admitted to the coronary care unit. In the coronary care unit, there were 10 deaths, giving a mortality of 25.6 per cent, while of the hospital patients, there were only 5 deaths giving a mortality rate of 8.8 per cent. The mortality rate for the 160 patients admitted to hospital more than 6 hours after the onset of infarction was 30 per cent and this was significantly greater (p > 0.025) than the mortality rate of those patients admitted to hospital under 6 hours. The average age of the patients admitted within 6 hours of the onset of severe pain was 55.5 years in the coronary care unit and 60.6 years in the ward beds. The mean age of the ten patients who died in the coronary care unit was 57.8 years, while the mean age of the 5 patients who died in ward beds was 64.2 years. Table V details the clinical state of the patients at the time of their first examination after admission to hospital. The 258 patients are divided into the coronary care
of myocardial
infarction
patients
765
group and the hospital group and it can be seen that all the deaths in the coronary care unit were in patients who had persistent lung crepitations at the time of their first examination and in those patients with cardiogenic shock. In the hospital group, 4 patients in whom there was no evidence of shock, crepitations, or elevation of the venous pressure, died, while one patient who had only elevation of the venous pressure succumbed. The other patients who died in the hospital group were those with evidence of persistent crepitations at the lung bases on admission or in those in whom cardiogenic shock occurred. Thus, the mortality rate for the hospital group, excluding patients with “cardiogenie shock,” is 17 per cent (27 of 163 patients), whereas for the similar coronary care unit group, the mortality rate is 14 per cent (8 of 59 patients). In a previous report from the same hospital,12 there was an 18 per cent mortality rate in patients treated in the coronary care unit and a 29.8 per cent mortality rate in patients treated in the general wards of the hospital when patients in cardiogenic shock were excluded. Discussion
In previous reports from the Royal Melbourne Hospital we have described the
Table V. Clinical severity in Classes1 to 4 determined at time of admission
Hosfdal
07
CC. U.
No shock, crefiitations, or elewalion of venous pressure
Persistent lung crepitations
Elevation of venous
Cardiogenic shock
Total
$wessure
Per cent of group Deaths Mortality rate (y,)
28 4 8
107 60 22 20.6
5 3 1 20
20 12 17 85
c. c. u. Per cent of group Deaths Mortality rate (%)
21 28 0 0
36 48 8 17
2 3 0 0
16 21 10 62.5
7.5
72
143
7
36
2.58
285 4
5.5 21 30
14 3 1
:t 27
24 62
Hos&taL
51
and C.C. LJ.) group Mortality Per cent ofrate (%) Deaths
Total
C.C.U.
(Hospital
= Coronary
care unit.
183 44 24
18 24
establishment of the coronary care unit.7~‘” There is little doubt that the recognition of cardiac arrhythmias at an early stage following acute infarction leads to more efficient treatment of patients with acute myocardial infarction. It is in this area of treating arrhythmias rapidly and efficiently that the coronary care unit has most clearly shown its effectiveness.395 Longterm survival following resuscitation from cardiac arrest occurring both in the coronary care unit and in ward beds attest to this improvement in medical management.8~gJ3 While it is recognized that acute myocardial infarction is the main cause of premature death in the population of the developed countries, there is very little accurate information about the clinical course of the condition in patients whether they are managed inside a hospital or in the home. In this paper we have reported some of the information gained from registering all persons admitted to the hospital with a provisional diagnosis of acute infarction together with those patients found in the hospital to have suffered a myocardial infarction. The patients registered were managed either in general ward beds or in a two-bed coronary care unit. We have analyzed certain characteristics of these two groups of patients separately and, in so doing, the differences between the groups have been highlighted. In emphasizing the difference between the patients, it was noted that the coronary care unit received fewer female patients and that the average age of the patients admitted to the coronary care unit was significantly less than the age of the patients in the hospital ward beds. While one would not wish to put an age limit on admission to a coronary care unit, it seems not unreasonable to admit the younger patients to the unit. Twenty-one per cent of the patients admitted to the coronary care unit had “cardiogenic shock” on admission compared with “cardiogenic shock” recorded in only 12 per cent of the patients admitted directly to a ward bed. These figures support the general concept that in many hospitals with a coronary care unit, the policy is to admit the more seriously ill patients to the spe-
cialized unit, these tending to “swamp” the unit with seriously ill patients who may not obtain great benefit from special care. In this review, the mortality rate in the “shocked” patients admitted to the hospital ward bed was higher than that among the patients admitted to the coronary care unit. This reflects some advantage in admitting the “shock” patient to the coronary care unit. However, the greatest value of the specialized coronary care unit relates to the treatment of the patients with acute infarction and cardiac arrhythmias and this value may be minimized by the unit receiving a very high proportion of patients with cardiogenic shock who only benefit to a small degree from the specialized treatment available in the coronary care unit. While it is beyond the scope of this report to make an objective assessment of the effectiveness of the coronary care unit in a hospital, it is considered that the maintenance of a register of patients coming into the hospital with acute manifestations of coronary artery disease will, in due course, make it possible to characterize those patients who will benefit most from being admitted to a specialized coronary care unit. This information will be of considerable value to those hospitals who are only able to maintain a small coronary care unit where a decision has to be made as to which type of patients should be admitted to the special unit. Accepting at this time that most clinical and statistical evidence supports the contention that the coronary care unit provides an area in which a patient with acute infarction can be given more effective treatment, then we have to decide on the value of admitting all patients with acute infarction to such a unit. In our series of 278 patients registered in the six-month period, 258 were allocated in Classes 1 to 4 and would definitely qualify for admission to a coronary care unit. The additional 20 patients who were registered in Classes 5 to 6 would also qualify for admission once diagnosed. This makes an estimated total of 556 patients in one year. Assuming a relatively even distribution of admission over the 12 months, the hospital would require a five-bed unit to keep each patient in the unit three days after admission.
Vaiume Number
73 6
No.ofA.M.1.
Hospital
registration
X averageno. ofdaysinunit 365
)
Due to the uneven distribution of patients, however, the unit would probably require an increment in beds of 25 per cent to cover the peaks of admissions. In patients over the age of 60 years, there was no difference between the mortality rates of the two sexes. In patients under the age of 60 years, there was, however, a noticeable difference in the mortality rate between the sexes with a significantly higher mortality rate in female patients. When a female under 60 years of age suffers an acute myocardial infarction, there is more severe involvement with a greater risk of death. The time of admission to the hospital following infarction had a noticeable effect on the hospital mortality rate. The patients admitted to hospital within six hours had a lower mortality rate than those admitted after six hours. This difference may be due to patients being admitted early (under six hours) because they had suffered an acute infarction and their medical advisor considered that they should be in the hospital, while those patients admitted after six hours were referred because they had suffered a complication of acute myocardial infarction. It is interesting to note that there was a higher hospital mortality rate among those patients admitted to the coronary care unit within six hours of the onset of their severe pain. This observation reflects the tendency to admit the more seriously ill, younger patient to the coronary care unit, particularly in the early stages after an acute myocardial infarction. Review of the initial clinical presentation related to hospital mortality rate (Table V) shows that the patient with evidence of cardiac decompensation on admission to hospital has less chance of survival. This relationship was evident irrespective of whether the patient was admitted to a hospital ward bed or to the coronary care unit. The register highlights the need for improved treatment of heart failure in all patients. It is interesting to note that when one excludes patients with cardiogenic shock, there does appear to be a reduction in mortality rate in patients treated in -:
of myocardial
infarction
patients
767
hospital wards from 29.8 per cenP to 18 per cent in the present report. While the method of identification of patients differed in the earlier report, the mortality reduction suggests improvement in the management of patients with acute infarction, not only in the coronary care unit, but also in the general hospital wards. Registration may make it possible to detect, within a hospital population, the form of treatment which will produce an alteration in survival. The data obtained from the registration of patients will help to provide a background of knowledge on which a rational plan of adequate hospital service can be provided. The establishment of coronary care units has given a suitable stimulus to the attempt to improve the management of patients with acute myocardial infarction. Initial published reports from the units emphasized the value of the new concept, however, it is now timely to examine the entire problem of the management of all patients presenting to the hospital with acute manifestations of coronary artery disease. Since the first units were established in 1962,2v6there have been important changes in the management of acute myocardial infarction with the introduction and wider use of drugs such as procainamide, propranolol, and lidocaine for the treatment of cardiac arrhythmias. The development of more potent diuretic drugs and the more rational use of digitalis in the management of cardiac decompensation has also evolved. With the availability of these drugs, there has been a widespread change in emphasis from the treatment of cardiac arrest to its prevention by the earlier and more aggressive management of arrhythmias4 coupled with the more enthusiastic treatment of patients with mild heart failure. It is against this background of changing therapy that the effectiveness of treatment of acute myocardial infarction should be assessed.It is considered that registration of patients within the hospital will indicate the areas where treatment still falls short and where it may be improved. Summary
Registration of 278 patients admitted to the Royal Melbourne Hospital during
768
Slomun und Brown
a six-month period with definite or suspected acute myocardial infarction has been achieved. One hundred and ninety-nine patients were admitted to general ward beds, while 79 patients were admitted to a two-bed coronary care unit. For the purpose of analysis, registered patients were placed in one of the six diagnostic classes recommended by the World Health Organization. A comparison of the patients admitted to hospital ward beds and to the coronary care unit emphasized the basic difference in the two groups of patients. The coronary care unit patients were younger, they had a higher incidence of cardiogenic shock on admission, and there was a higher mortality rate among those patients admitted to the unit within six hours of the onset of their severe pain. The over-all hospital mortality rate was 24 per cent in the patients admitted to the ward beds and to the coronary care unit. The register provides a background of information on which the effectiveness of the management of patients with acute myocardial infarction can be assessed. We thank the Medical Staff of the Royal Melbourne Hospital for permission to study patients in their care. We thank Miss Janice Ferguson who was responsible for the initial registration of all patients. We also thank Dr. E. B. Cross and Dr. Ted Cooper of the United States Public Health Service for their continued support of the project.
2. 3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
REFERENCES 1.
Cross, E. B.: in Julian, D. G., and Oliver, Acute myocardial infarction, Edinburgh, E. & S. Livingstone, Ltd.
M. F.: 1968,
14.
ljaq, 1~1.: Preliminary studies in the acute coronary care area, J. Lancet 83:53, 1963. Lawrie, D. N., Higgins, N. Ii., Godman. M. J., Oliver, N. F., Julian, D. G., and Donald, K. W.: Ventricular fibrillation complicating acute myocardial infarction, Lancet 2:523, 1968. Lawn, B., Fakhro, A. M., Hood, W. B., Jr., and Thorn, G. W.: The coronary care unit: New perspective and directions, J. A. M. A. 199:188, 1967. Lown, B., and Vassaux, C.: Lidocaine in acute myocardial infarction, AMER. HEART J. 76586, 1968. Meltzer, L. E.: Coronary units can help decrease hospital deaths, Mod. Hosp. 104:102, 1965. Robinson, J. S., Sloman, G., and McRae, C.: Continuous electrocardiographic monitoring in the eariv stages after acute myocardial infarction, Med. Jr Aust. 1:427, 1967. Robinson. 1. S.. Sloman. G.. Mathew. T. H.. and Gable, A. J.: Survival after resuscitation from cardiac arrest after myocardial infarction, AMER. HEART J. 69:740, 1965. Robinson. I. S.. and Sloman. G.: Resuscitation from cardiac arrest after myocardial infarction, Med. J. Aust. 1:578, 1965. Rockwell, M. A.: A summary of medical literature describing the effectiveness of coronary care units. RM-5944-Rand CorDoration. 1969. Rose, G. A., and Blackburn, H. : ‘Cardiov&cular survey methods, World Health Organization Monograph Series No. 56, 1968. Sloman, G., Stannard, M., and Goble, A. J.: Coronary care unit-A review of 300 patients monitored since 1963, AMER. HEART J. 75:140, 1968. Stannard, Mary, and Sloman G.: Ventricular fibrillation in acute myocardial infarction: Prognosis following successful resuscitation, AMER. HEART J. ‘X:573, 1969. W.H.O. Euro .5010(l), 1968: Ischaemic heart disease registers, Report by a Working Party, Copenhagen, 1968. I”
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