LEFT HEART FAILURE

LEFT HEART FAILURE The clinical picture of left heart failure is distinctive and should not be readily confused with any other condition—with one exception. Cardiac asthma is well named, since the urgent, commonly nocturnal, dyspnoea of left ventricular failure is associated with bronchospasm in a considerable proportion of cases. This may lead to confusion with bronchial asthma—a serious error which may cost the patient his life as the treatment of the two conditions is quite different. It is particularly important before administering morphine to a suspected case of left ventricular failure to ensure that the diagnosis is correct since the giving of morphine to a patient with bronchial asthma may prove fatal.
Treatment of left heart failure is a matter of great urgency. The patient may recover spontaneously from his attack or may die in the course of half an hour. Efficient remedies are available and prompt intervention may save life.
The time-Honoured remedy for cardiac asthma is morphine, and provided the diagnosis is certain, its administration is safe and effective. The dose depends on the weight of the patient and the route of administration. An average subcutaneous dose is 15 mg. but this may be increased to 20 mg. in heavily built adults. The action of the drug is apparent in 15 to 30 minutes. A much speedier action is obtained by intravenous injection, and for this purpose a correspondingly smaller dose is desirable, say 10 mg. (^ gr.) given slowly. The effect appears within two or three minutes and the doctor may at his discretion repeat the same or a smaller dose in say 15 minutes should he decide that further treatment is desirable. Since attacks of cardiac asthma commonly occur early in the morning and the prac¬titioner is called from his bed to attend the desperately ill patient, it is probably wise to resort to the intravenous route and for the doctor to sit by the bedside of the patient till the full effect has been achieved.
Aminophylline is also a valuable drug in this condition : although it stimu¬lates the respiratory centre it causes relaxation of the bronchioles and thus gives relief from dyspnoea. When there is any shadow of doubt as to the nature of the attack, aminophylline is the drug of choice. It is given by slow intravenous injection, well diluted in 10 ml. of saline, in a dose of 0-5 g. The action is prompt and usually dramatic.
If facilities are at hand, the administration of oxygen by a disposable plastic mask is highly effective. The rate of administration should be from 4 to 6 litres per minute.
In an emergency when no drugs are available venesection may be life saving. The amount of blood withdrawn should be from 10 to 20 oz. (300 to 600 ml.), but the essence of the procedure is the rapid withdrawal. For this purpose a wide-bore French's needle is thrust through the skin into the ante-cubital vein, and the procedure is cleaner if a length of rubber tubing has been attached to the needle so that the blood may drain into a container. In an emergency the ante-cubital vein may be snipped with scissors or nicked with a scalpel to allow the escape of blood. The arrest of bleeding is readily achieved by applying pressure with a pad and bandage. The effectiveness of venesection depends on the sudden reduction in the venous return to the right heart; this reduces right ventricular output and diminishes pulmonary congestion, thus enabling the overloaded left heart to cope with the influx from the lesser circulation. It follows that a " bloodless venesection " achieved by reducing the venous return through cuffs applied to the four limbs may achieve a similar result and this without the hazard of inducing anasmia should the procedure require to be repeated. For this purpose two ordinary sphygmomanometer cuffs are applied to the arms and two broad cuffs to the thighs. These are pumped up to a pressure somewhat above the venous pressure to obstruct the venous return. It is important, however, that when the patient has recovered from the acute attack the cuffs should not all be released simultaneously, since the sudden flooding of the right heart with the trapped blood may cause a recurrence of pulmonary congestion. It is wiser to release the cuffs one by one while keeping the patient under close observation.
In severe cases of pulmonary oedema there is great exudation of fluid into the lungs and constant cough with profuse watery pink-stained expectoration-In such cases much benefit can be achieved by suction, applied through 2 catheter passed into the pharynx or (in the unconscious patient) into the trachea.
In hospital the catheter can be connected to a suction apparatus, commonly an electric motor and pump, but alternative improvised methods may have to be used.
The treatment of the acute attack by no means completes the treatment of left heart failure : the patient who has suffered such an attack is in as much need of intensive treatment with digitalis and diuretics as any other patient with cardiac failure. Many patients, particularly in the middle-aged hypertensive group, are intolerant of restriction and feel so well the next morning that they wish to return to work. They must be firmly dissuaded from doing so and should be treated by rest in bed for some three to four weeks. Digitalization may be achieved rapidly with i mg. digoxin intravenously; the administration of diuretics will be necessary and they should be given as already described for congestive heart failure (p. 574). Further, in all patients who have suffered an attack of left heart failure the underlying cause must be identified and treated. For example, if the cause is hypertension, this should be treated by hypotensive drugs : if the attack has been precipitated by a myocardial infarction this will determine the further treatment. The patient tn whom the attack is secondary to a mitral stenosis should be assessed carefully with a view to surgical valvotomy, and if the valve is considered anatomically suitable for section operation should be undertaken with the minimum of delay. Postponing operation even for a few days may lead to a relapse of left heart failure and prove fatal. In this as in every other cardiac condition a precise and complete diagnosis is of prime im¬portance. To label a patient " cardiac asthma " without identifying and dealing with the underlying cause is clearly inadequate.