MYOCARDIAL INFARCTION

MYOCARDIAL INFARCTION
The immediate treatment of a patient with a myocardial infarction may be considered under three headings : the relief of pain ; the management of shock; and in exceptional circumstances, the resuscitation of the apparently dead.
Relief of Pain and Removal to Hospital.—The immediate treatment consists in securing absolute rest in bed and the relief of pain by administration of morphine in full doses. Should the attack occur when the patient is at work or away from home, he should immediately be given hypodermically 15 to 20 mg. of morphine and should be sent home or to hospital or nursing home by car or ambulance. He must be assisted to undress, and should from the outset be spared all avoidable exertion. It is unwise to allow a woman to undertake single-handed the nursing of a relative or other patient with this disorder. The day and night nursing and the lifting involved impose too great a strain, and the patient is naturally disposed to ease the burden by doing things for himself. It is wiser to send the patient to hospital at the outset than to move him some days later.
The amount of morphine required to relieve pain is variable. The initial dose of 15 to 20 mg. should be repeated without hesitation in an hour should pain be unrelieved, and a further dose is likely to be required during the first 24 to 48 hours. In severely shocked patients caution must be exercised since lack of effect from repeated subcutaneous injections may be due to non-absorption of the drug. For the later doses oral administration of the 15 mg. (I gr.) tablets by an attendant under medical direction, is satisfactory. A limit is set to dosage only by the development of general toxic symptoms, for the drug exerts no deleterious effect on the heart. Morphine is invaluable because it relieves pain and abolishes anxiety : adequate doses of the drug are, therefore, conducive to sleep, and complete rest is of prime importance in restoring the cardiac reserve. Nausea and vomiting are common symptoms in heart failure— including the acute failure often seen in myocardial infarction—and they can be relieved completely by giving morphine. However, these symptoms also commonly occur as after-effects of morphine—especially in women so that it is wise to give an anti-emetic such as cychzine along with it. It is, therefore, important to assess accurately the significance of nausea and vomiting and to be more cautious in the doses given to old people.
Treatment of Shock.—Shock in cases of coronary occlusion varies markedly in degree. Profound shock develops in a minority of cases with massive infarcts, and in general is associated with a grave prognosis and a rather intractable course. Some desperately ill patients, however, do respond to treatment and may go on to a smooth convalescence, so that every effort should be made in every case. It is in these severely shocked patients that oxygen administration is of conspicuous value. To be effective, it should be given in high concentration (say 6 to 7 litres per minute) continuously for many hours by means of a polythene mask.
Large intravenous infusions carry a serious hazard from overloading a damaged myocardium, and adrenaline, ephedrine and posterior pituitary extracts are contraindicated on account of their cardiac actions. Noradrenaline has a marked vasoconstrictor action without the cardiac accelerator and aug-mentor actions of adrenaline. The drug raises the blood pressure through its peripheral action without a significant stimulant action on the heart. It is given intravenously by drip in a concentration of 8 mg. per litre. The rate of infusion is regulated according to the blood pressure response and is generally of the order of 10 mcg. per minute. In addition to this hormone there is nov available a number of synthetic pressor agents (e.g. metaraminol) administerec in the same way by intravenous drip, and these have been extensively investigateii-Unfortunately the initial expectations have not been justified by results and the mortality among patients with severe shock, despite such treatment, varies in the reported series from 60 to nearly 100 per cent. The writer's personal experience has been correspondingly disappointing, and he places more faith in the administration of oxygen than in the use of pressor drugs.
Intensive Care Units and Cardiac Resuscitation.—Every patient who has suffered a major myocardial infarction is, particularly during the first few crucial days, at risk of sudden death from cardiac arrest or ventricular fibrillation. Modern electronic devices and the techniques of external cardiac massage and mouth-to-mouth artificial respiration, have led to many apparently hopeless cases being rescued. Time is of the essence for successful resuscitation, since after cardiac arrest lasting some four minutes only irreversible brain damage ensues. It is essential, therefore, that the onset of an attack is signalled at once, and that all staff (nurses, students and junior doctors) should be familiar with the life-saving temporary measures employed while skilled help and modern apparatus are summoned.
The practicability of saving such patients has led to the institution in larger hospitals of Intensive Care Units, to which patients at risk can be admitted, and where monitoring and resuscitation equipment are available. It is possible for an alarm signal (light or buzzer) in the nurses' station to be triggered by the patient's heart rate falling below or rising above predetermined figures, and for electrical pace-making to cut in automatically in cases of ventricular standstill. If ventricular fibrillation is demonstrated on the oscilloscope, defibrillation is attempted by external electrodes or by their direct application to the exposed heart. The gross metabolic acidosis which develops rapidly in such patients must be corrected by intravenous bicarbonate or lactate, otherwise attempts to restore cardiac action are fruitless. The staff of such units must all be trained in resuscitation procedures. Short of such units, suitable equipment can be mounted on a trolley, which is brought to the scene of the emergency in response to an alarm call to the telephone exchange, the operator simultaneously sum¬moning medical help (anaesthetist, registrars, etc.).
The proportion of patients saved is at best low, but the few successes amply compensate for the labour and expense involved. Ethical problems naturally arise—e.g. how far one is justified in attempting resuscitation in old, ill subjects far advanced in serious cardiac or other disease. Nevertheless, many " coronary deaths " occur in young men, and in such the full resources of modern therapy must be deployed.
Treatment of Myocardial Infarction during the First Month.—The best guide to the practitioner in handling a patient with myocardial infarction is a knowledge of the natural history of the disease so that, aware of the hazards besetting the patient, he may be ready to forestall disaster or treat complications. By far the largest number of deaths occur within the first twenty-four hours after onset and a high percentage of the remainder within the first week. There¬after they are relatively infrequent and scattered more evenly over the first six weeks. Figure 4 shows graphically this striking predominance of deaths in the early hours and days. On analysis the major causes of death are recurrence of infarction, abnormal rhythms, left heart failure and persistence of intractable shock. These, therefore, are the conditions which it must be our aim to treat. The later deaths result from congestive cardiac failure or left ventricular failure,. from systemic or pulmonary embolism, and from cardiac rupture, while recurrent infarction accounts for a smaller number. Accordingly, during the later weeks therapy should be directed towards prevention or treatment of these various complications.
Prevention of Recurrent Infarction.—In patients in whom the infarction is caused by a coronary thrombosis, it would be logical to prevent spread or recurrence of such clotting by the administration of anticoagulant drugs. The pros and cons of anticoagulant treatment are discussed more fully on p. 589. Such treatment cannot of itself have any direct effect on the death rate from such complications as persistent shock, dangerous arrhythmias or left sided heart failure.

Anticoagulant Therapy.—Anticoagulants have been used for some 20 years in the management of the acute phase of myocardial infarction but there is still much controversy as to their value. Extreme views for and against their
•use are held : there are those who regard the withholding of anticoagulants from a patient with mvocardial infarction as tantamount to malpractice, and on the other hand there are physicians who regard these drugs as poisons with no place in therapeutics. As usual the truth probably lies midway between these extremes, and the author believes that anticoagulants as a class have a definite though limited value. They cannot be expected to be effective in reducing the mortality from shock, arrhythmias or cardiac failure, and from time to time cases of relapse of infarction do occur in patients under anticoagulant treatment in whom the standard tests for prothrombin time indicate adequate therapeutic action. One of their main effects is the reduction in thrombo-embolism and there is general agreement that they affect a significant reduction in mortality from this cause. -.
Assessment of their value in treatment of this condition has proved difficult, since many factors interfere with a straightforward evaluation. For example, if patients are admitted to hospital on the second or a later day after infarction, then. whatever method of treatment is employed the overall mortality will be lower than in patients admitted on the first day of illness, since those treated are the survivors of the first supremely dangerous 24 hours. Again, variations due to the age and sex of the patient, to the severity and extent of the infarction, and to the condition of the heart muscle before infarction occurred introduce major
•complicating factors. It is only by comparison of a large series of treated and untreated (control) cases, carefully matched in respect of all these factors (age, sex, severity, degree of shock, duration of illness, etc.), that a reliable impression '
•can be obtained as to their value. Many such series have been published, some comprising very large numbers of cases, and widely divergent assessments of the value of these drugs have been reached. Generally the most striking benefits are in men around the age of fifty who have had no serious previous myocardial lesion. By contrast in patients over seventy of either sex, and in those who have suffered a series of previous infarctions with consequent scarring of the- muscle, the effect is by no means striking.
Some physicians divide cases of myocardial infarction when first seen into “good risk " and " bad risk " classes. The bad risk patients are those who display persistent pain, severe shock, arrhythmias or failure, who have had previous myocardial infarctions, or who suffer from some systemic disorder such as diabetes. The good risk group are those who have none of these ominous features. It is claimed that among good risk patients the mortality without anticoagulant treatment is so low that the risks attendant on its use are unjus¬tifiable, and this treatment can be reserved for patients who are in the bad risk group. The writer believes that this is an unjustifiable simplification, since we deal with individuals and not with groups. A patient when first seen may be little shocked and display all the criteria of a small infarction, and yet in the course of 24 or 48 hours may develop an extension of his lesion and rapidly acquire many of the characteristics of the bad risk case. Nor is it possible to predict in which individual this deterioration may occur. For this reason patients with myocardial infarction in the younger age-group (up to sixty-five years) should be given anticoagulant treatment when the condition is first diagnosed, irrespective of the severity of the original attack. When there are other visceral lesions, however, anticoagulants are contraindicated. Fatal hzemorrhage has occurred in a patient who has had no dyspeptic symptoms for over a decade, but with an old peptic ulcer history; and similar disasters have occurred from cerebrovascular embolic accidents complicating the coronary attack before admission to hospital.
All patients receiving anticoagulants must be kept under close clinical observation for signs of over-dosage (purpura, lowered capillary resistance, microscopic hasmaturia) and at the same time accurate estimations of blood coagulation time and/or prothrombin index must be done. The known antidotes should be at hand. It is generally safe for a single intitial intravenous dose of heparin (15,000 units) to be given by the practitioner as soon as he has established the diagnosis of coronary occlusion. Continuation of the treatment and its laboratory control can be achieved in hospital.
It is usual to administer heparin for 48 hours after admission to hospital, meantime giving phenindione orally. Thereafter the action of phenind'ione is sufficient for the heparin to be discontinued. Treatment with phenindione should be continued for two to four weeks depending on initial assessment of severity and duration of rest in bed, and then the dose is gradually tapered off. The daily dose varies from 25 to 150 mg. according to the blood prothrombin level.
Other Treatment.—Vasodilators are useless in myocardial infarction, and should not be given, particularly as shock is commonly severe and the blood pressure already low.
The type of diet recommended for cases of severe congestive failure will prove generally suitable ; it is easily taken and readily assimilated.
Purgation should be avoided. The instillation of two ounces of olive oil into the rectum, followed by a saline enema in. the morning, is a safe and effective method of opening the bowels.
Duration of Rest in Bed.—The duration of confinement to bed varies with the severity of the case. Where intense and prolonged pain, profound shock and the electrocardiographic pattern of transmural infarction indicate an extensive lesion involving the whole thickness of the ventricular wall, the patient should be kept in bed for six weeks. There are real risks to life through¬out the first few weeks in such a case (recurrence, embolism, rupture of the softened area of muscle, failure), and these are increased by exertion. After six weeks or so these risks are greatly reduced, and a gradual return to activity can be permitted. On the other hand, a single attack of pain lasting half an hour> not associated with shock, and with an electrocardiogram indicating a limited area of superficial damage only, would warrant a cautious return to activity in two to three weeks. In all cases the patient is first allowed to wash and feed himself, to sit up in bed for meals and later to rise to the toilet. Eventually he should be up and walking about in his room for a few hours daily. The question of his future activities must then be considered. -
Difficulty will often be experienced in persuading a patient to stay in bed for the prescribed period, since frequently he feels perfectly well within a few days. The difficulty is naturally greatest in mild cases, or in patients who have had no pain. Explanation that the heart has been damaged, and that it takes some weeks to heal properly, will usually render the patient amenable to discipline. But one must be careful not to induce a state of undue apprehension of the hazards, for much anxiety may result and more harm than good be done. The attitude of the doctor towards his patient is important. The patient is generally aware of the seriousness of his condition. An attitude of unrelieved gloom on the part of the attending physician is both inhuman and unjustifiable. The risks to be run during convalescence must be kept in mind but must not be used as a bogev to frighten a patient into submission. Not the least of the patient's risks is that of developing a cardiac neurosis which may be more crippling than his organic lesion.
Patients who have suffered an attack of coronary thrombosis, whether or not residual angina of effort persists, should in their after-care be treated on the same lines as the subjects of effort angina.