Emergency care for AMI at the prehospital stage should be aimed at:
- adequate pain relief;
- renewal of the patency of the damaged vessel, prevention of reocclusion (repeated cessation of blood circulation);
- maintaining patency of the coronary arteries, reducing platelet aggregation;
- limitation of the ischemic zone, prevention or elimination of complications.
What is thrombolysis and how is it done?
Thrombolysis (TLT) is the process of dissolution of a thrombus under the influence of an enzyme introduced into the systemic circulation, which causes the destruction of the base of the thrombus.
Drugs for TLT (tissue plasminogen activators) are divided into direct (Streptokinase) and indirect (Alteplaza, Aktilize, Tenecteplaza).
In the mechanism of action of TAP, 3 stages are conventionally distinguished:
- Binding of the enzyme to plasminogen, which is located on fibrin (formation of a triple complex);
- TAP promotes the penetration of plasminogen into fibrin, converting it into plasmin;
- The resulting plasmin breaks down fibrin into small fragments (destroys a blood clot).
There is a direct relationship between the time of initiation of TLT and the prognosis for the patient. In the guidelines of the European Association of Cardiology, it is indicated that thrombolysis should be carried out up to 12 hours from the onset of the disease (further administration of the drug is inappropriate).
TLT procedure activates platelets, increases the concentration of free small blood clots. Therefore, TLT should be performed in conjunction with adjuvant antiplatelet therapy.
Tenecteplase is used for TLT at the prehospital stage. It is administered as an intravenous bolus (intravenous jet, using a syringe) for 10 seconds. This TAP of the third generation, which has a high safety profile (low risk of hemorrhagic and hemodynamic complications, allergic reactions), does not require specific storage conditions and is easy to use.
Alteplase is administered in a hospital setting. After the introduction of 5 tis OD of heparin, 15 mg of the drug is injected bolus. Then they switch to drip injection of 0.75 mg / kg for 30 minutes and 0.5 mg / kg for 60 minutes. The total dose is 100 mg. The entire procedure is carried out with a continuous infusion of heparin.
Streptokinase is injected intravenously at a dosage of 1.5 million OD diluted per 100 ml of saline for 30-60 minutes. Before using the drug, a bolus of 5 thousand OD of heparin is administered, followed by resumption of the infusion not earlier than 4 hours after the end of the streptokinase administration.
According to the order of the Ministry, after TLT, the patient must be taken to a specialized hospital with the possibility of balloon angioplasty or stenting no later than 12 hours.
Indications for
Indications for thrombolysis in myocardial infarction are:
- Long-term (more than 20 minutes) anginal attack in the first 12 hours from its onset;
- ST segment elevation by 0.1 mV or more in two adjacent standard or 0.2 mV in adjacent pericardial ECG leads;
- Complete blockade of the left bundle branch, which arose for the first time in the presence of pain.
TLT is indicated in the absence of the possibility of performing PCV within 90-120 minutes from the moment of the first contact with the patient.
Thrombolysis in the case of myocardial infarction has the right to be performed by a specialized cardiological ambulance team equipped with everything necessary to relieve possible complications.
Contraindications
Absolute contraindications for thrombolysis in myocardial infarction:
- Postponed hemorrhagic stroke less than 6 months ago;
- History of TBI, surgery up to 3 weeks;
- Gastrointestinal bleeding less than 1 month ago;
- Disorders of the blood coagulation system;
- Aortic dissecting aneurysm;
- Refractory arterial hypertension (SAT over 200 mm Hg, DAP over 110 mm Hg).
Relative contraindications:
- TIA less than 6 months ago;
- Systematic use of direct anticoagulants;
- Pregnancy, the first 28 days after childbirth;
- Punctured vessels of large diameter inaccessible for compression;
- Long-term traumatic cardiopulmonary resuscitation;
- Recent laser therapy for fundus retinal diseases;
- Liver failure;
- Peptic ulcer in the acute stage;
- Infective endocarditis;
- Diabetic hemorrhagic retinopathy and other retinal hemorrhages.
The doctor is obliged to warn the patient about all possible contraindications and complications of the procedure. The patient confirms his consent to TLT in writing in the protocol for thrombolysis.
Possible complications of thrombolytic therapy (occur in no more than 0.7% of cases):
- Parenchymal hemorrhage, bleeding at the injection site;
- Acute rhythm disturbances - atrial fibrillation is considered as an indicator of recanalization (restoration of blood circulation) of the vessel;
- Allergic reaction, fever.
Clinical criteria for successful reperfusion (renewal of oxygen supply) of the myocardium:
- Rapid regression of pain syndrome;
- Manifestations during the introduction of a thrombolytic agent of reperfusion arrhythmias;
- Involution of ECG changes (approach of the ST segment to the isoline;
- Decrease in the level of cardiospecific biochemical markers of necrosis.
The time of day also affects the effectiveness of TLT - recanalization is worse in the morning. At this time, platelet activity, coagulation processes, blood viscosity, vasomotor tone and natural inhibition of fibrinolysis have the maximum daily indicators.
Conclusions
Thrombolytic therapy is included in the list of standard measures in the care of patients with acute coronary syndrome at the prehospital stage. The use of TLT in the first hours after the onset of AMI symptoms can save patients with potentially necrotic myocardium, improve left ventricular function and reduce the mortality rate from AMI. The risk of retrombosis (re-blockage) is reduced by the combination of thrombolysis with heparin therapy and long-term use of Aspirin.
