Treatment of myocardial infarction
The general plan of management of patients with myocardial infarction can be presented in the following form:
- To stop the pain syndrome, calm the patient, give aspirin.
- Hospitalize (to deliver to BIT).
- Attempt to restore coronary blood flow (reperfusion of the myocardium), especially within 6-12 hours from the onset of myocardial infarction.
- Measures aimed at reducing the size of necrosis, reducing the degree of violation of the function of the left ventricle, preventing recurrence and repeated myocardial infarction, reducing the incidence of complications and mortality.
Pain relief syndrome
The cause of pain in myocardial infarction is ischemia of the viable myocardium. Therefore, all therapeutic measures aimed at reducing ischemia (reduction of oxygen demand and improvement of oxygen delivery to the myocardium) are used to reduce and stop pain: inhalation of oxygen, nitroglycerin, beta-blockers. First, if there is no hypotension, take nitroglycerin under the tongue (if necessary, again at intervals of 5 minutes). In the absence of the effect of nitroglycerin, the drug of choice for the management of the pain syndrome is morphine-IV 2-5 mg every 5-30 minutes before the pain is relieved. Inhibition of respiration from morphine in patients with severe pain syndrome with myocardial infarction is very rare (in these cases, iv injection of nalorphine or naloxone is used). Morphine has its own anti-ischemic action, causing dilatation of veins, reduces preload and reduces the need for myocardium in oxygen. In addition to morphine, the most commonly used promedol - iv in 10 mg or fentanyl - iv in the 0,05-0,1 mg. In most cases, to the narcotic analgesics add Relanium (5-10 mg) or droperidol (5-10 mg under the control of blood pressure).
A common mistake is the appointment of non-narcotic analgesics, for example, analgin, baralgin, tramal. Non-narcotic analgesics do not possess anti-ischemic action. The only excuse for using these drugs is the lack of narcotic analgesics. In the guidelines for the treatment of myocardial infarction in most countries, these drugs are not even mentioned.
In case of hard-to-stop painful pain, re-introduction of narcotic analgesics, the use of nitroglycerin infusion, the appointment of beta-blockers are used.
Intravenous infusion of nitroglycerin is prescribed for non-occlusive pain syndrome, signs of persistent myocardial ischemia, or stagnation in the lungs. Infusion of nitroglycerin begins at a rate of 5-20 μg / min, if necessary, increasing the rate of administration to 200 μg / min under the control of blood pressure and heart rate (blood pressure should be not less than 100 mm Hg, and heart rate not more than 100 per min). Caution should be exercised when prescribing nitroglycerin to patients with myocardial infarction of the lower location (or not to prescribe at all) - possibly a sharp drop in blood pressure, especially with concomitant myocardial infarction of the right ventricle. A common mistake is the appointment of nitroglycerin to all patients with myocardial infarction.
In the absence of contraindications, beta-blockers are prescribed as early as possible: propranolol (obzidan) iv 1-5 mg, then inside 20-40 mg 4 times a day; metoprolol - in / in 5-15 mg, then metoprolol orally 50 mg 3-4 times a day. You can go to take atenolol - 50 mg 1-2 times a day.
All patients with the first suspicion of myocardial infarction showed an earlier appointment of aspirin (the first dose of aspirin 300-500 mg must be chewed and washed with water).
Coronary thrombosis plays a major role in the occurrence of myocardial infarction. Therefore, thrombolytic therapy is pathogenetic in myocardial infarction. Numerous studies have shown a reduction in mortality with thrombolytic treatment.
Forty years ago, hospital mortality in myocardial infarction was about 30%. The creation of intensive care units in the 1960s made it possible to reduce hospital mortality to 15-20%. With the optimization of medical measures, the use of nitroglycerin, beta-blockers, aspirin, a further reduction in mortality was observed with myocardial infarction - up to 8-12%. Against the background of the use of thrombolytic therapy, mortality in a number of studies was 5% or lower. In most studies with the appointment of thrombolytics, there was a decrease in mortality by about 25% (on average from 10-12% to 7-8%, ie in absolute figures by about 2-4%). This is comparable to the effect of the appointment of beta-blockers, aspirin, heparin, indirect anticoagulants, ACE inhibitors. Under the influence of each of these drugs, there is also a decrease in mortality by 15-25%. The use of thrombolytics can prevent 3 to 6 deaths in 200 treated patients, the appointment of aspirin - the prevention of about 5 deaths, the use of beta-blockers - the prevention of approximately 1-2 deaths in 200 treated patients. Perhaps the simultaneous use of all these drugs will further improve the results of treatment and prognosis for myocardial infarction. For example, in one study, the administration of streptokinase led to a 25% reduction in mortality, aspirin use by 23%, and their joint appointment reduced the lethality by 42%.
The main complication of thrombolytics are bleeding. Expressed bleeding is relatively rare - from 0.3 to 10%, including cerebral hemorrhages in 0.4-0.8% of patients, an average of 0.6% (ie 6 cases per 1000 patients treated - 2-3 times more often than without the use of thrombolytics). The frequency of strokes with the use of preparations of the tissue activator plasminogen is greater than against the background of streptokinase (0.8% and 0.5%). When using streptokinase, allergic reactions - less than 2% and a decrease in blood pressure - in about 10% of patients are possible.
Ideally, the time from the onset of myocardial infarction symptoms to the onset of thrombolytic therapy ("call-to-needle" time) should not exceed 1.5 hours, and the time from admission to the hospital before the start of thrombolytics (time from door to needle) - not more than 20-30 minutes.
The question of the introduction of thrombolytics at the prehospital stage is decided individually. In the recommendations for management of patients with myocardial infarction in the US and Europe, it is considered more appropriate to conduct thrombolytic therapy in a hospital. The reservation is made that if the time of transportation of the patient to the hospital is more than 30 minutes or the time to the expected thrombolysis exceeds 1-1.5 hours, it is permissible to conduct thrombolytic therapy at the prehospital stage, i.e. In the conditions of first aid. Calculations show that the implementation of thrombolytic therapy in the prehospital stage allows to reduce mortality in myocardial infarction by approximately 20%.
With iv injection of streptokinase, reperfusion begins in about 45 minutes. Recovery of coronary blood flow occurs in 60-70% of patients. Signs of successful thrombolysis include cessation of pain, rapid ECG dynamics (return of the ST segment to the isoline or a decrease in the height of the ST segment by 50%), and a second increase in the activity of CKK (and MB CK) approximately 1.5 hours after streptokinase administration. At this time, the occurrence of reperfusion arrhythmias - most often, ventricular extrasystoles or an accelerated idioventricular rhythm, but also increases the incidence of ventricular tachycardia and ventricular fibrillation. If necessary, standard medical measures are taken. Unfortunately, early reocclusion occurs in 10-30% of patients.
The main indication for the appointment of thrombolytic therapy is considered to be ACS with ST segment elevation in 2 or more adjacent leads or the appearance of left bundle branch blockade in the first 6 hours from the onset of symptoms. The best results were found in patients with anterior myocardial infarction, with the registration of ST rise in 4 or more leads and at the beginning of the drug administration during the first 4 hours. During thrombolysis during the first hour of myocardial infarction, there was a decrease in hospital mortality in more than 2 times (there are reports of a decrease in mortality with successful thrombolysis during the first 70 minutes from 8.7% to 1.2%, ie 7 times (!) - "golden" hour). However, the inflow of patients during the first hour is extremely rare. Decrease in mortality is noted with thrombolytic therapy within 12 hours from the onset of myocardial infarction. With the preservation of the pain syndrome and the recurrence of ischemia, thrombolytics are used within 24 hours of the onset of symptoms of MI.
In patients with ACS without ST segment elevation and with myocardial infarction without a Q wave, the use of thrombolytics was not indicated; on the contrary, deterioration (increase in mortality) was noted.
The main absolute contraindications to the use of thrombolytic therapy are: active or recent internal bleeding, a hemorrhagic stroke in the anamnesis, other disorders of cerebral circulation for 1 year, signs of possible aortic dissection. The main relative contraindications: surgical operations for 2 weeks, prolonged resuscitation (more than 10 min), severe arterial hypertension with blood pressure above 200/120 mm Hg. St., hemorrhagic diathesis, exacerbation of peptic ulcer.
Currently, streptokinase is the most accessible and the most studied drug. Streptokinase does not have an affinity for fibrin. Streptokinase is administered as an intravenous infusion of 1.5 million units for 60 minutes. Some authors recommend to enter streptokinase more quickly - for 20-30 minutes.
In addition to streptokinase, the action of the recombinant tissue plasminogen activator (TAP, alteplase) has been studied quite well. TAP is a fibrin-specific thrombolytic. The introduction of alteplase is somewhat more effective than streptokinase, and allows the additional saving of one patient in the treatment of 100 patients. Reteplase is also a recombinant form of TAP, with slightly less fibrin specificity. The reteplase can be injected intravenously. The third drug, tenecteplase, is also a TAP derivative.
Less studied the effect of drugs APCAK (anestreplase, eminase), urokinase, prourokinase and other thrombolytics.
In Russia, streptokinase is most commonly used because it is 10 times cheaper and in general it's not much inferior to tissue activators of plasminogen for its effectiveness.
Surgical methods of coronary blood flow restoration
Approximately 30% of patients with myocardial infarction have contraindications for the appointment of thrombolytics and 30-40% have no effect on thrombolytic therapy. In specialized departments, some patients on the first 6 hours after the onset of symptoms receive urgent balloon coronaroangioplasty (CAP). In addition, even after successful thrombolysis, the overwhelming majority of patients have residual coronary artery stenosis, so attempts have been made to perform KAP immediately after thrombolytic therapy. However, in the randomized trials, the advantages of this approach are not revealed. The same can be said for urgent aortocoronary shunting (CABG). The main indications for KAP or CABG in the acute period of myocardial infarction are complications of myocardial infarction, primarily postinfarction angina and heart failure, including cardiogenic shock.
In addition to relief of pain syndrome, inhalation of oxygen and attempts to restore coronary blood flow, all patients with the first suspicion of the possibility of myocardial infarction prescribe aspirin in a loading dose of 300-500 mg. Further, aspirin is taken at 100 mg per day.
Opinions about the need to prescribe heparin in uncomplicated myocardial infarction against the background of thrombolytics are quite contradictory. Intravenous administration of heparin is recommended for patients who do not undergo thrombolytic therapy. After 2-3 days pass to the SC administration of heparin at 7.5-12.5 thousand units ED 2 times a day subcutaneously. Intravenous infusion of heparin has been shown in patients with advanced anterior myocardial infarction, with atrial fibrillation, with a clot in the left ventricle (under the control of coagulation rates). Instead of conventional heparin, subcutaneous administration of low molecular weight heparins can be used. Indirect anticoagulants are prescribed only in the presence of indications - an episode of thromboembolism or an increased risk of thromboembolism.
All patients, in the absence of contraindications, are prescribed beta-blockers as early as possible. With myocardial infarction, the use of ACE inhibitors has also been shown, especially in the detection of left ventricular dysfunction (ejection fraction less than 40%) or signs of circulatory insufficiency. With myocardial infarction, there is a decrease in total cholesterol and LDL cholesterol ("reverse phase reactant"). Therefore, normal indices indicate an increased level of lipids. Most patients with myocardial infarction should be prescribed statins.
In some studies, a positive effect of the use of cordarone, verapamil, magnesium sulfate and a polarizing mixture in myocardial infarction was revealed. Against the background of taking these medications, there was a decrease in the frequency of ventricular arrhythmias, recurrent and repeated myocardial infarctions, as well as a reduction in the mortality of patients with myocardial infarction (with a follow-up of up to 1 year or more). However, there are not enough reasons for recommending the routine use of these drugs in clinical practice.
Management of patients with MI without a Q wave is almost identical to the management of patients with unstable angina (acute coronary syndrome without ST segment elevation). The main drugs are aspirin, clopidogrel, heparin and beta-blockers. In the presence of signs of an increased risk of complications and death or the absence of the effect of intensive drug therapy, a coronagraphography is shown to assess the possibility of surgical treatment.
Myocardial infarction: treatment
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