Changing perspectives in coronary care

Changing Perspectives in Coronary Care A Five Year Study* ROBERT L . MACMILLAN, M .D ., F .R .C .P . (C),t KENNETH W . G . BROWN, M .D ., F .R .C .P

(C), F A .C .C ,`

GERALD B . PECKHAM, M .D ., F .R .C .P.(C), OTTo KAHN, M .D ., D . BARRY HUTCHISON, M .D . and MARLEICH PATON Toronto, Canada

IVE years ago, the death rate among patients admitted to the Toronto General Hospital with acute myocardial infarction was approximately 40 per cent . Because of this high mortality, an intensive care ward for study and treatment of patients with this condition was put into operation in March 1962 . This is a report of the first five years' experience in this unit .

the diagnosis and control of cardiac arrhythmias . They were accepted because the monitoring facilities provided by the unit were not available elsewhere in the hospital . The remaining 1,114 patients were admitted with the provisional diagnosis of acute myocardial infarction, subsequently confirmed in 789 patients (71%J;) . The criteria for diagnosis were the classic clinical picture, elevation of serum transaminase (SGOT) and electrocardiographicc changes . Q waves in the electrocardiogram were not required when typical -T and T wave alterations were accompanied by the other criteria . In 29 per cent of the patients, the diagnosis of recent myocardial infarction was not established ; the majority were known to have pre-existing coronary disease and had an abnormal electrocardiogram . They were considered to have had prolonged myocardial ischemic pain without infarction . The 789 patients with proved acute myocardial infarction form the basis of this report.

F

s

METHODS AND MATERIAL The coronary unit consisted of a four-bed room and an adjacent nursing station .' A continuous electrocardiogram was recorded by a Grass inkwriting pen recorder (Fig . 1) . This method gave more complete information about arrhythmias than that obtained by intermittent sampling, or by a tape memory-loop activated by an alarm device . The continuous 24 hour record of all 4 patients was reviewed in approximately an hour . Interesting findings were clipped from the record and saved ; the rest was discarded . Nurses have played a very important role in the operation of the unit. All nursing was done by qualified graduate nurses who received special instruction in acute myocardial infarction and in the recognition of arrhythmias in the electrocardiogram . They also received training in resuscitation procedures and in the care of patients with artificial pacemakers . Weekly conferences were held to maintain a high level of competence and enthusiasm . Case Material : Initially our interest centered on the mode of death and attempts to restore life by prompt resuscitation of victims of cardiac arrest . Between March 13, 1962, and March 12, 1967, there were 1,367 admissions to the coronary unit (Table t) . Of these patients 253 were not suspected of having recent myocardial infarction but were admitted for

RESULTS MECHANISM OF DEATH During the early months of this study, it became apparent that the electrical activity of the heart often continued for many minutes after the point of clinical death, and during this period various "postmortem rhythms" were recorded . For example, ventricular fibrillation, previously considered to be present in most patients with acute myocardial infarction at the time of death, frequently appeared after the patient had been clinically dead for some minutes . At the time of death, the electrocardiogram frequently showed little gross changes other than disappearance of the P wave . The QRS complexes continued unaltered in rate or

* Front the Department of Medicine, University of Toronto and the Toronto General Hospital . This work was supported by the Ontario Heart Foundation . f John Oille Scholar in Cardiology . I Rykert Research Cardiologist . VOLUME 20, 0c10BER 1967

451

452

MacMillan et al .

PIG . 1 .

Four channel ink-writing electrocardiograph

for continuous monitoring of patients in the coronary care unit at

Toronto General Hospital .

form for several minutes before gradually slowing and widening . We have called this sinus arrest with a lower (nodal) pacemaker . The mechanism of death in 130 patients who were monitored up to and at the moment of clinical death is presented in Table it . The patients fell into two main groups of approximately equal size . The first group was described as sudden death and referred to patients apparently convalescing satisfactorily when they TABLE I

Experience of Toronto General Hospital Coronary Unit March 13, 1962, to March 12, 1967

abruptly lost all vital signs . Two thirds of these patients had ventricular fibrillation or rapidly fatal ventricular tachycardia . The primary fault appeared to be a sudden disruption of the electrical control of the heart beat . In the other group, death came more gradually over several hours or days, due to failure of the mechanical "pumping action" of the heart, with features of cardiac failure, refractory hypotension or frank cardiogenic shock . This was associated with a higher incidence of atrial arrest and other types of suppressed pacemaker activity. RESUSCITATION

Year

Admissions

1962-63 1963-64 1964-65 1965-66 1966-67 Totals

247 289 256 314 261 1,367

Myocardial For EGG Monitor Infarction Only Unproved Proved 17 65 50 59 62 253

84 48 45 85 63 325

Figures in parentheses are per cent .

(36) (21) (22) (33) (31) (29)

146 176 161 170 136 789

Resuscitation is defined as recovery with the patient leaving the hospital alive at the end of convalescence . Originally, hopes were high that resuscitation measures would permit salvage of most victims of cardiac arrest in the coronary unit . Our results have been disappointing ; only 16 were salvaged over the five year period . This represents a success rate of approximately 15 per cent of all attempts . Procedures for resuscitation were applied to I HE AMERICAN JOURNAL OF CARDIOLOGY



Changing Perspectives in Coronary (,are TABLE It

and the duration of monitoring influence the

Correlation Between the Terminal Heart Rhythm and Clinical State in 130 Monitored Patients Who Died`

Sudden Heart Rlryslim Ventricular Iihril4tion Ventricular tachycardia AI=iw arrest, lower por rzn ker A-V hl-4

need, 32' 8 4)

Co u plat ((yr ole Sir-

5

Atria] fibrillation 'Totals

1 60

Monitored

up

I

453

40 14

Progressive Ford Shock or No . of Ilcart Failure Paticou 10t 3 271 12 l

13 49

1 70

53 31 17

131,

to and during the point of clinical death_

patients with mechanical failure as well as to those with electrical failure . Only the latter have responded . The patients who were resuscitated had a relatively favorable prognosis train the beginning, since only 1 had signs of congestive failure, and no patient was in shock (Table nt) . Only 1 was receiving digitalis . Nachlas and \Miller= have reviewed the literature and found successful resuscitations reported in 5 to 15 per cent of attempts . Higher rates have been reported by Day and Averill . 3 Robinson et al . 4 have also shown aa high degree of success in the resuscitation of patients with ventricular fibrillation who were admitted with what appeared to be a mild myocardial infarction without complications such as shock and failure. In comparing the results of resuscitation from various centers, one must take into consideration the condition of patients admitted to the unit, whether or not attempts at resuscitation were restricted to patients with ventricular fibrillation and whether patients with brief Stokes-Adams attacks have been included . We have included 3 patients with Stokes-Adams attacks and ventricular standstill where life had to be maintained by closed cardiac massage for at least three minutes .

figures from center to center . 'l' he 300 patients were monitored for an average period of five days . We did not include patients with sinus tachycardia, sinus bradycardia, or first degree A-V block (prolongation of P-R interval) . The terminal arrhythmias in patients who died have also been excluded, Of these 300 patients, 216 (72%Jn ) had an arrhythmia either on admission or during their stay in the unit (Table Iv) . Ventricular ectopic beats were most frequent and were considered to be an arrhythmia when they occurred more often than 6/min . Ventricular tachycardia was defined as a burst of three or more ventricular ectopic beats in sequence . With our monitoring technic, this arrhythmia was recorded in 99 patients . Twothirds of these bursts of ventricular tachycardia lasted less than 5 seconds . Usually, the patient was unaware of the change, and without continuous monitoring the episodes would have passed unnoticed . An example of this type of

TABLE 1n

Condition of 16 Patients Successfully Resuscitated (Discharged from Hospital Alive) from Cardiac Arrest Following Acute Myocardial Infarction Ventricular fibrillation Ventricular standstill In shock In heart failure Average age Average success rate

13 3 0 1 (mild) 57 1 in 6 attempts

No successes in "lower pacemaker' or mechanical

failure .

TABLE IV

Arrhythmias That Appeared During Continuous Monitoring" in 216 (72%) of 300 Consecutive Patients with Proved Acute Myocardial Infarction No . of

ARRHYI'HMIAS

Continuous electrocardiographic monitoring revealed arrhythmias in a surprisingly high proportion of patients with acute myocardial infarction . This led to the second phase of our investigation, namely, a study of the arrhythmias in 300 consecutive patients with proved acute infarction . The reported incidence of observed arrhythmias varies considerably s Differences in the definition of the terns arrhythmia, variation in monitoring technics (continuous or intermittent sampling) VOLUME 20, OCTOBER 1967

Arrhythmia Ventricular tachycardia Ventricular ectopic beatst Aerial fibrillation or flutter Heart block (2nd or 3rd') Atrial tachycardia Miscellaneous (S-A block, A-V dissoc ., BBB, APB's)

Patients 99 70 49

36 12 31

* Average 5 days . { Over 6/min . S-A = sino-atrial ; dissoc . = dissociation ; BBB = bundle branch block ; APB = atrial premature beat .



MacMillan et al .

454

Sinus

rhythm

120/mm .

Asymptomatic

Flo . 2 .

Occasional VYB

3 second V .T .

aL 200/min .

An asymptomatic episode of ventricular tachycardia

(lower strip) recorded on the monitor 24 hours after admission of a 33 year old man for acute myocardial infarction ; VPB = ventricular premature beats . (V .T .)

ventricular tachycardia is shown in Figure 2 . Two thirds of the patients with this arrhythmia had infarction of the anterior surface of the left ventricle ; the number of anterior and posterior infarcts in this series was approximately equal . Decision to administer antiarrhythmic drugs to these patients was left to the discretion of the attending physician . Early in the study there was a tendency to ignore this arrhythmia . In 34 patients who were not given antiarrhythmic drugs, there were 12 deaths and 22 survivors . In the remaining 65 patients treated with procainamide or quinidine, there were 13 deaths . This was not a controlled study, however, and since there were more complications which might have led to death in the nontreated group, valid conclusions on the value of TABLE V

Incidence of Heart Block (Second or Third Degree) in 300 Consecutive Patients with Acute Myocardial Infarction Location of Infarct

No . of Patients

No .

Deaths °Jo

Anterior Posterior Totals

14 22 36

8 6 14

57 27 39

TABLE VI

Relation Between Arrhythmias and Mortality in 300 Consecutive Patients with Acute Myocardial Infarction

No arrhythmia Single arrhythmia Multiple anhythmias Totals

HE = heart failure .

o . of Patients

Deaths

Mortality (%)

incidence of Shock, HF or Both (%)

84 82 134 300

11 19 48 78

23 35 26

27 40 55 42

No.

antiarrhythmic drugs cannot be drawn . The fact that two thirds of the patients with untreated short bursts of ventricular tachycardia survived suggested that this arrhythmia, per se, was frequently benign . Nevertheless, the current practice is to treat all patients with this arrhythmia without delay . If the ventricular premature beats occur more often than 6/min ., it is now customary to give antiarrhythmic medication . Second or third degree A-V block was recorded in 12 per cent of the patients and was attended by a higher mortality (Table v) . There was a greater tendency for this arrhythmia to occur in patients with posterior myocardial infarction . The appearance of heart block in a patient with an anterior infarct was ominous . Temporary transvenous pacing by either bipolar catheter or unipolar wire pacemaker was used in patients with second or third degree heart block . The patients who survived usually had a return of normal A-V conduction . Only 1 of 36 patients in this group required a permanent pacemaker . Atrial fibrillation and atrial flutter occurred without relation to the location of the infarct . The ventricular rate was slowed with digitalis, and emergency cardioversion was not undertaken in this group . The mortality of patients with atrial arrhythmias was only 18 per cent . Arrhythmias and Mortality : In this group of 300 patients the presence of an arrhythmia was associated with a more serious prognosis (Table vi) . In the 84 patients with sinus rhythm throughout their stay in the unit, the mortality was 13 per cent . When a single arrhythmia occurred once or repetitively, the mortality was 23 per cent . Two or more types of arrhythmia in the same patient were associated with a 35 per cent mortality . These figures emphasize the interrelation between abnormalities of heart rhythm and prognosis . However, as seen in Table vi, the incidence of arrhythmia was parallel to the occurrence of shock or heart failure, which also influence mortality unfavorably . Moreover, in these patients the frequent use of vasopressor drugs and digitalis may have contributed to the higher incidence of arrhythmias . In such patients it was impossible to decide whether the arrhythmia played a primary role in determining the outcome or was merely secondary to other factors . MORTALITY TRENDS

Mortality statistics for the 789 patients with THE AMERICAN JOURNAL OF CARDIOLOGY



4 55

Changing Perspectives in Coronary Care proved infarcts include deaths occurring in the

'TABLE Vii

unit and after transfer to other parts of the hospital . A high percentage (51%) of the deaths occurred during the first 48 hours (Table vu) . By the end of the fifth day, 68 per cent of the deaths had occurred . After two weeks, deaths were infrequent . In Table vin the deaths are shown by year . During the first two years, the hospital mortality was 36 and 37 per cent, compared with 27, 26 and 22 per cent for the succeeding three years. This reduction in mortality was due to

'Timing of 235 Deaths in 789 Patients with Proved Acute Myocardial Infarction

Is,

tiarrhythmic drugs was increased (Table ix) . At present, more than half the patients receive one or more of these agents . It is tempting to attribute the lowered mortality to the more frequent use of antiarrhythmic drugs . However, it is important to realize that conditions may not be strictly comparable year after year, even in the same hospital . The characteristics of the patients for each year are shown in Table x . The average age and sex distribution have remained more or less constant. Cardiogenic shock was more frequent during the first and fifth years, while the incidence of congestive heart failure fluctuated without any definite trend . The possible influence of other less tangible variations must be kept in mind . Initial heparin therapy was used in most patients in 1962 and 1963 6 but has since been abandoned . The interval between onset of pain and arrival at the hospital, the number of patients dead on arrival, or dying in the emergency room, and the availability of beds for transferring patients out of the unit may vary from year to year . Over the years, there has been increasing alertness to the toxic arrhythmias from digitalis and other drugs and improved management of cardiac failure . In view of the foregoing, one must be cautious in ascribing the changing mortality to any single factor of treatment . VOLUME 20, OCTOBER 1967

3rd-5th 6th-10th Day Day

Iv .

N..ofpts . ,,, . Pt'

121

40

51

17

After 15th Uay 'total

Us,

38 16

2275 100

= paliema .

fewer deaths during the first 48 hours . Patients were kept in the unit for a minimal period of 48 hours . At that time, the decision to transfer the patient out of the unit was based on his clinical state, the availability of accommodation elsewhere in the hospital and the need for a bed in the unit for an incoming patient . Although the average stay in the unit was five days, the initial 48 hours afforded the most uniform interval for comparison year by year . Factors Influencing Mortality : Midway during the second year, when the high incidence of arrhythmias was recognized, the use of an-

=rime of Death n m15th

48

TABLE VIII

Mortality in Patients with Proved Acute Myocardial Infarction March 13, 1962, to March 12, 1967

Nn.

Year

Cases

1962-63 1963-64 1964-65 1965-66 1966-67 Torah

146 176 161 170 136 789

Total 52 65 44 44 30 235

(36) (37) (27) (26) (22)

(30)

Deaths Pi's' 4811r.

After 48IIr .

34 (23) 32 (18) 22 (14) 20 (12) 13 (10) 121 (16)

18 (13) 33 119) 22 (13) 24 (14) 17 (12) 114 (141

.

Figures in parentheses are per cent .

TABLE IX

Mortality and Use of Antarrhythmic Drugs in Proved Acute Myocardial Infarction

Year

Total No . Patients

Deaths in First 48 Hr .

1962-63 1963-64 1964-65 1965-66 1966-67

146 176 161 170 136

34 (23) 32 (18) 22(14) 20(12) 14 (10)

Figures in

pares Wcscs

Patients Given Quinidine. Procainamirlc, or Lidocaine 21 (14) 30 (17) 15 (31) 85 (50) 78(57)

arc per cent.

TABLE X

Year by Year Comparison of Patients Admitted to the Coronary Unit

Year

No.

Average Age (yr .)

1962-63 1963-64 1964-65 1965-06 1966-67

146 176 161 170 136

60 61 60 61 .5 59

women (%)

Shock (%)

Failure (%)

28 32 28

28 20 15 19 24

46 37 55 45

44



456

MacMillan et al . DiscussloN

The five year experience at the Toronto General Hospital has demonstrated the advantages of an intensive care coronary unit for the treatment of acute myocardial infarction . By specialization, the level of nursing care achieved has been higher than was previously possible . Having patients with similar problems together in one area has been most economical in terms of staff and equipment . New knowledge concerning the cause of death has been acquired . It was found that sudden electrical death due to ventricular fibrillation or tachycardia occurred less frequently than gradual death due to mechanical failure of the heart . Patients resuscitated following cardiac arrest form a small but gratifying group, and while this may be increased slightly in the future, it is unlikely to have a marked effect on mortality . Monitoring by the continuous ink-writing electrocardiograph has been very satisfactory . A surprisingly high incidence of arrhythmias has been encountered . Recently, Lown et al 7 have stressed the importance of early detection and treatment of minor disorders of rhythm with a view to preventing cardiac arrest . In some centers, the coronary care unit is primarily an arrhythmia unit . While we recognize the importance of this approach to treatment, in many of our patients with arrhythmias the abnormal rhythm did not appear to be the primary factor leading to death . Moreover, there was an appreciable mortality among patients without arrhythmias ; in these patients, death was due to mechanical failure of the heart . Undue emphasis on the arrhythmias must not lead us to ignore this other important group of patients . Further studies are needed to detect impending mechanical failure . Both medical and surgical measures for supporting the failing myocardium must be explored . SUMMARY During a five year period (1962-67), 789 patients with proved acute myocardial infarction have been treated in the coronary unit of the Toronto General Hospital . The average stay in the unit was five days . With continuous electrocardiographic monitoring, 72 per cent of patients were shown to

have an arrhythmia . While the appearance of an arrhythmia was associated with a graver prognosis, the concomitant presence of other complications often made it difficult to assess the exact role of the arrhythmia and the benefit from treatment with an antiarrhythuuc drug . In a study of 130 patients who died, it was found that about half died of an electrical (arrhythmic) disorder and the remaining half of mechanical failure of the heart . Only 16 patients with cardiac arrest responded to resuscitative measures . All 16 patients successfully resuscitated had electrical failure . The over-all mortality was 30 per cent ; about half the deaths occurred in the first 48 hours . The mortality in the first 48 hours after admission has fallen from 23 per cent during the first year to 10 during the fifth year . This encouraging trend must be interpreted with caution because there were many uncontrolled variables . Vigorous treatment of the arrhythmias has assumed an important place in the management of acute myocardial infarction . The present challenge is to study and improve the treatment of the large group of patients who die from the effects of a failing myocardium . REFERENCES

1 . BROWN, K. W. G ., MACMILLAN, R . L ., FORBATH, N ., MEL'GRANO, F . and SCOTT, J . W . Coronary unit-an intensive care center for acute myocardial infarction . Lancet, 2 : 349, 1963 . 2 . NACHLAS, N. M. and MILLER, D . L Closed chest cardiac resuscitation in patients with acute myocardial infarction . Am . Heart J., 69 : 448, 1965 . 3 . DAY, H. W . and AvERILL, K . Recorded arrhythmias in an acute coronary care area . Dis. Chest, 49 : 113,

1966 . 4 . ROBINSON, J . S ., SLOMAN, G . and MATIIEw, T . IL Survival after resuscitation from cardiac arrest in acute. myocardial infarction . Am. Heart J., 69 :

740, 1965 . 5 . Yu, P . N ., Fox, S . M ., IMBOnEN, C . A . and KILLIV, T. Coronary care unit . L A specialized intensive care unit for acute myocardial infarction . Mod. Concepts

Cardiovas. Dis ., 34 : 23, 1965 . 6 . BRowN, K . W. G . and MACMILLAN, R . L. A critical evaluation of initial heparin therapy in acute myocardial infarction. In : Anticoagulant Therapy in Ischaemic Heart Disease, p . 70 . New York, 1965 . Grune & Stratton . 7 . LowN, B ., FAKHRO, A . M ., Hoon, W . B ., JR . and THORN, G. W. Tile coronary care unit, new perspectives and directions. J.A .M.A ., 199 :188,

1967.

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