Monitoring Requirements in Patients with Acute Myocardial Infarction
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Postgrad Med J: first published as 10.1136/pgmj.46.536.380 on 1 June 1970. Downloaded from Postgraduate Medical Journal (June 1970) 46, 380-387. Monitoring requirements in patients with acute myocardial infarction A. A. JENNIFER ADGEY J. F. PANTRIDGE Research Fellow Physician-in-Charge Cardiac Department, Royal Victoria Hospital, Belfast, Northern Ireland Summary the deaths from myocardial infarction occur outside The majority of deaths from myocardial infarction hospital (Spiekerman et al., 1962; Kuller, Lilienfeld occur soon after the onset of symptoms. The mobile & Fisher, 1966), and there is little doubt that most scheme described allows intensive care to commence of these deaths are due to ventricular fibrillation. in the patient's own home or at the site of infarction Yet the median time between onset of symptoms and and thus reduces the interval between the onset of admission to a hospital coronary care unit is more symptoms and the initiation ofintensive care. Monitor- than 8 hours (Fig. 1, curve B) (McDonald, 1968). ing is continued during transport and following admis- The Belfast study (McNeilly & Pemberton, 1968) sion to the hospital coronary care unit. showed that of 901 individuals who had a fatal The major impact of therapy on the mortality from coronary attack in the year surveyed, only 414 acute myocardial infarction will result from the detec- reached hospital; 109 were dead on arrival. Experi- tion and correction of rhythm disturbances. ence in North London (Nixon, 1968) showed that of the patients who died within the first 24 hr of THE MAJORITY of deaths from acute myocardial myocardial infarction, 47% did so before an ambu- copyright. infarction occur soon after the onset of symptoms. lance arrived; 13% died during transit and only 40% Sixty per cent of the deaths occur within 1 hr of the ofthe deaths in the first 24 hours occurred inhospital. onset of symptoms (Yater et al., 1948; Bainton & Since the majority of deaths occur early and since Peterson, 1963). A survey in Belfast in 1965 showed there is usually a considerable delay in hospital that over 40% of the deaths from acute myocardial admission it would seem that although hospital infarction occur within the first hour (Fig. 1, curve coronary care units reduce the hospital mortality, & The such units will not have a profound effect on the A) (McNeilly Pemberton, 1968). majority of http://pmj.bmj.com/ overall mortality. If the greater part of the delay in Or 1100 hospital admission resulted from delay in the patient seeking medical help, then little could be done about the early high mortality. However, the data of McNeilly & Pemberton indicate that patient delay is J not the major factor. They found that the median . -I time between the onset of symptoms and request for medical help was for males 1 hr 17 min and for on September 29, 2021 by guest. Protected 50- 4- 50 females 1 hr 6 min. Many other factors are involved in the delay in the initiation of intensive care. The ~OA /A/ I <[ family doctor may be unaware of the high risk of sudden and preventable death in the patient with an -I apparently mild coronary attack. The ordinary ambulance service may not always be capable of dealing with the call immediately. Much time may 100 Lt II J 0 elapse between the patient's arrival at the hospital 2 4 8 12 casualty or admission area and his transfer to a Hours after onset coronary care unit. It was thought possible to re- FIG. 1. The time-relationship of deaths from acute myo- move all causes of delay apart from that due to the cardial infarction and the admission pattern to hospital patient's failure to seek immediate medical aid. It coronary care units. seemed that this diminish with Curve A constructed from the data of McNeilly & Pem- patient delay might berton (1968). increasing public awareness of the importance of Curve B constructed from the data of McDonald(1968). seeking medical help promptly. Postgrad Med J: first published as 10.1136/pgmj.46.536.380 on 1 June 1970. Downloaded from Monitoring patients with acute myocardial infarction 381 .. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ..... "..~:..:~.::.::.':.:~......::....'~...:'~~~~~~~~~~~~~~~~~~~.~.n;~F'~!!~...... FIG. 2. Plan of Hospital Area. A: Ambulance depot R: Rendezvous point T: Telephone exchange W: Ward. When the mobile unit commenced operation in mobile unit immediately, and before he has seen the Belfast on 1 January, 1966 (Pantridge & Geddes. patient, ifhe considers that a message he has received 1966, 1967) the family doctors in the city (population indicates the probability of myocardial infarction. copyright. 550,000) were informed of the facts concerning early The majority of calls come from the family doctors. deaths and were given instruction in resuscitation A proportion of the calls do however come from the methods. The family doctors were given a special general public, usually because the patient or his telephone number. Calls to this number get to the relatives are unable to contact the general practi- coronary care ward (Fig. 2, W) directly and thus tioner. The screening of such calls is undertaken by delays at the hospital telephone exchange are the coronary care unit personnel. Ifthe family doctor avoided. A short-wave radio system is used to ensure reaches the patient before the mobile unit, he will that a junior doctor receives the call immediately. initiate immediate therapy for the relief of pain and http://pmj.bmj.com/ The main ambulance depot for the area is located in for bradyarrhythmia or ventricular dysrhythmia. the hospital grounds (Fig. 2, A). When ambulance The practitioners have been given precise instruc- control is activated an ambulance proceeds to point tions as to the therapy to be employed in such cir- R (Fig. 2). When it arrives there, a junior doctor and cumstances. When the team arrives, electrocardio- a nurse from the coronary care unit will have graphic monitoring is commenced and therapy con- reached this point. The team is on its way within tinued in the patient's own home or at the site of the 2 min of the receipt of the signal from the family attack. The patient is not moved until a stable doctor. The ambulance carries the usual equipment rhythm is established. on September 29, 2021 by guest. Protected found in a hospital coronary care unit, monitoring It seems likely that in many situations initial and resuscitation equipment including a battery- monitoring can be carried out by the general practi- operated DC defibrillator and pacing catheters. All tioner and so we have been developing a small, equipment is portable. When the team reaches the inexpensive oscilloscope (Fig. 3). A tele-equipment patient in his own home or at the site of attack he is Type S51B oscilloscope weighing 141 lbs with a long under the same intensive care conditions that obtain glow phosphor screen is used as shown here. A small in a hospital coronary care unit. Fifty per cent of the ECG amplifier is built utilizing linear operational patients are reached within 10 min of receipt of the integrated circuits. This high-input impedance call from the family doctor. amplifier has a lower 3DB point at 1 cycle/sec and an The major objective ofa mobile coronary care unit upper limit 3DB point at 100 cycles/sec. For safety as of coronary care units in hospitals, is the preven- requirements the ECG amplifier is transformer- tion of death from rhythm disturbance since it is isolated from the oscilloscope circuit and Zener likely that the majority of coronary deaths occurring diodes are used to limit the power supply output. soon after the onset of symptoms result from ventri- A defibrillation protection circuit is also fitted to the cular fibrillation. The family doctor may call for the input circuit. This protection circuit is fitted to all Postgrad Med J: first published as 10.1136/pgmj.46.536.380 on 1 June 1970. Downloaded from 382 A. A. Jennifer Adgey and J. F. Pantridge our monitoring equipment. This monitor gives a 5" visual display and can be produced for £60. Monitoring and therapy are continued during transport to the hospital coronary care unit (Fig. 4) thus removing the risk of arrhythmic death during transit. Haste or fuss during transit is most carefully :.. avoided. There has been no death :0\ coronary during I~:~~il:iiiii.!·- transport in the period of nearly 4 years of the unit's :-:::::::w -.· operation. I·I~IP- - :li:i8ia::e:n::":'r:::::::i::·::~~~~~~~~~~~~~~~~~~~~~~~~Xt.. Within the period 1 January, 1966 and 31 October, is· 1969, there have been 2529 calls for the mobile unit and during this period 1072 patients with indubitable myocardial infarction have been managed by the unit. The diagnosis of infarction was considered established when (a) there was indubitable electro- cardiographic evidence of recent infarction or sequential ST or T wave changes accompanied by significant and transient rise in serum glutamic oxalacetic-transaminase or (b) left bundle branch block with similar enzyme changes. The time after the onset of symptoms at which the 1072 patients came under intensive care is shown in Fig. 5. 265 (25%) came under intensive care within 1 hr, 553 (52%) within 2 hr and 803 (75%) within 4 hr. Fig. 6 shows that over the 31 year period increasing numbers of have come under intensive care patients copyright. early. FIG. 3. Portable oscilloscope for use by the family Bradyarrhythmia is frequent among those seen doctor. early. Forty-six per cent of patients with posterior http://pmj.bmj.com/ :.:··:: ,:.·· iiii·iifiii.·'.:. :.·:··· ·:· ·.·:· ''':':'''' '.' .': ii yBp8a%lsalssllesrssea%esl.aasprp.s.ii re er::l-·:.·.··:·· ::·I i.s".sleaa%rrsa%sns.····9;..6;;rTi EEi:iiil:·::··.· i:.''''':: .