Lecture on the treatment of acute myocardial infarction with ST elevation

2021-08-06 09:46 PM

Conventional 12-lead recording only detects 85 percent of acute myocardial infarction, so additional V7, V8, and V9 should be recorded if a posterior myocardial infarction is suspected, adding V3R, V4R


Myocardial infarction is necrosis of a single area (>2cm2) of the myocardium due to occlusion of a coronary artery. The most common is the left coronary artery (40% anterior interventricular branch and 25% left exponential branch). Right coronary artery only 35%.


It is most often caused by a blood clot that forms on the atherosclerotic plaque, if the plaque is partially dislodged, it is easier to form a thrombus.

Rarely due to coronary artery spasm or Emboli.


Diagnosis (+) is based on 3 groups of symptoms:

Chest pain.

Cardiac enzyme changes.

EGC transform.

The presence of 2 out of 3 symptom groups is sufficient to diagnose (+) acute myocardial infarction


Chest pain: often severe, continuous, pain behind the sternum, may radiate to the left chin, left shoulder, the inner surface of the left arm and fingers 4, 5, may radiate to the epigastrium, does not relieve with rest and nitrates.

However, acute myocardial infarction can also have intermittent pain, left chest pain or epigastric pain, mild pain or even no pain, especially in postoperative patients, diabetes, the elderly, or high blood pressure... .

Acute heart failure.

Heart shock.


Conventional 12-lead recording only detects #85% of acute myocardial infarction, therefore additional V7 V8 V9 should be recorded if post-true MI is suspected (high R V1) and additional V3R V4R if infarction is suspected. right ventricular myocardium.

The progression of acute myocardial infarction is very dynamic, so it is necessary to record ECG many times.

Q wave:

Typical: width > 0.04s and amplitude > 1/4 R

Non-Q-wave myocardial infarctions are less common and are usually subendocardial.

Change ST - T.

ST-elevation and convexity upward, T wave accompanies the ST segment to form the arch of PARDEE.

There are many other chest pain conditions that also change ST-T:

Myocarditis: ST elevation, concave, Q wave.

Pericarditis: ST elevation, T (-).

Aortic dissection: ST elevation or descent or nonspecific changes.

Pneumothorax: rS from V1 -V4, ST changes, T are not specific.

Pulmonary embolism: ST depression, S1 Q3.


Lower back: D2, D3, aVF.

After real: V7, V8, V9.

In front of the wall: V1, V2, V3 (V4)..

Anterior to the apex: V4 (V3, V5).

Front side: V5, V6, aVL, D1.

Wide front: V1 => V6, aVL, D1.

Deep septum: V1, V2, V3 (V4), D2, D3, aVF.

Right ventricle: V1, V3R, V4R, aVF, D3.





Heart yeast (Biomarkers)


Starting to increase

Reached peak concentration

Back to normal


3 - 12h


48 - 72h

Troponin I

3 - 12h


5 - 10 days

Troponin T

3 - 12h

12 - 24h

5 - 14 days


1 - 4h

6 - 7h





1-2 weeks


Mortality of patients with acute myocardial infarction due to both arrhythmias and cardiac pump failure. Timely detection and treatment of fatal arrhythmias reduce hospital mortality. The majority of in-hospital mortality of MI is in patients with severe ventricular dysfunction and cardiogenic shock because myocardial necrosis develops within hours. Early restoration of perfusion with fibrinolysis or PTCA reduces infarct size and preserves left ventricular function. Numerous clinical trials have shown that giving thrombolytics reduces mortality, especially when treatment is started within 4 hours of onset.


Pain relief.


Reduce the size of the necrotic area.

Treatment of complications: shock, heart failure, arrhythmia, ...

Prevention of recurrent myocardial infarction.

Pain relief

Morphin sulfate:

Doses of 2.5 - 5 mg intravenously slowly may be repeated after 10 minutes until the pain is controlled, but should not exceed 30 mg/day.

Contraindications: Low blood pressure, bad consciousness, respiratory failure, caution in people over 70 years old...

Rapid-acting nitrates such as Risordan 5 mg or Nitroglycerin 0.4 - 0.6 mg are sublingually repeated after 5 minutes if the pain is still present (if SBP ³ 95 mmHg).

Breathe oxygen

4-6L/min through the nasal cannula.

If there is heart failure, give a high dose of oxygen 8-10 L/min or through mask 80-100% oxygen.

Thrombolytic drugs

For ST-segment elevation myocardial infarction, it is important to re-establish circulation in the occluded coronary artery as soon as possible with thrombolytic agents or primary revascularization.

The fibrinolytic drug has a thrombolytic effect, it restores 60-90% of coronary artery flow. However, the drug has a good effect if used in the first 6 hours, if it is more than 12 hours, there is no effect.


There are bleeding lesions.

Recent surgery or major bleeding < 10 days.

There are diseases at risk of bleeding: systolic blood pressure > 180 mmHg, diastolic blood pressure > 100 mmHg, peptic ulcer...

There are 3 groups of drugs that are recognized to be effective:

rt-PA (recombinant tissue plasminogen activator) is the best

Start 5-10mg IV then 60mg in the first hour, every second and third hour continue 20mg, 100mg total dose.


Dosage: 1.5 million UI mixed in 100ml of 9% NaCl intravenously for 1 hour.


(an isolated plasminogen streptokinase activator complex)

Dosage: 30mg intravenously over 2-5 minutes.



The average use time is about 5 days.

UFH: 25,000UI in 2 divided doses every 12 hours intravenously. Monitor TCK 2 times normally.

Since low molecular weight heparin is recommended for less bleeding events, Enoxaparin (Lovenox) is initiated intravenously at 30 mg, followed by 1 mg/kg subcutaneously every 12 h.

Anti-platelet aggregation:

Aspirin: 162 - 325 mg initially, then 75 - 160 mg/day

Clopidogrel (Plavix) loading dose 300 mg then 75 mg/day.

Intravenous antiplatelet therapy GP IIb/IIIa inhibitors are also beneficial in the treatment of patients with unstable angina or non-ST-segment elevation myocardial infarction.


The effect of reducing pain and reducing the size of the infarct area.

Initially, you should use a fast-acting type such as Riordan 5mg or Nitroglycerin 0.4 - 0.6mg sublingually... then switch to the long-acting type.

Caution in case of hypotension: it is necessary to raise blood pressure with vasopressors before using nitrates


Beta-blockers reduce oxygen consumption by reducing heart rate and myocardial contractility, thus reducing the size of the necrotic area.

Contraindications: bradycardia < 55 beats/min, systolic blood pressure < 95 mmHg, atrioventricular block, heart failure, obstructive pulmonary disease.


Intravenous metoprolol 5mg x 3 times 5 to 10 minutes apart, then 50-100mg/12h.

Propranolol 1mg IV /10 minutes x 3 times then 20-40mg orally every 8 hours

ACE inhibitor

ACE inhibitors improve outcomes after acute myocardial infarction. Initiate ACE inhibitors within 24 to 48 hours of acute MI in patients with prior MI, diabetes mellitus, anterior myocardial infarction on ECG, tachycardia, and X-ray presentation of left heart failure or EF < 45%.

Calcium Inhibitors

For patients with chest pain after myocardial infarction and with contraindications to Beta-blockers.

Dosage: Must start with a low dose.

Treatment of high blood pressure

Hypertension needs to be treated quickly, the measures chosen are as follows:

Rest in bed, relieve pain, sedation.

Beta-blockers if there are no contraindications.

Inhibition of ACE.

Inhibit calcium when the above steps do not work.

Intravenous infusion of Nitroprusside or Nitroglycerine if the above steps fail.

Treatment of complications

The two most common fatal complications are arrhythmia and mechanical (heart failure).


Predominantly ventricular fibrillation, the main cause of death in the first hours and later also in the form of sudden death. It is through early detection and resolution of ventricular fibrillation that coronary care units have reduced in-hospital mortality from 30% to 10-20%.

Ventricular extrasystoles:

Only treat when ventricular extrasystoles > 5 beats/min, R/T, sequence, varied. Lidocaine can be administered intravenously 1mg/kg, may be repeated 3 times followed by an intravenous infusion of 2-4 mg/min. If lidocaine is not effective, use procainamide 500-1000 mg IV loading dose < 50 mg/min, then maintain 2-5 mg/min. Alternatively, amiodarone can be used, but with caution when used with beta-blockers, which can lead to an atrioventricular block.

Ventricular tachycardia:

Intravenous injection of lidocaine 50-100mg, 1-2 times is not effective, should give an electric shock.

Ventricular fibrillation:

Electric shock and medication see the treatment of ventricular fibrillation.

Sinus Fast:

It is necessary to find and treat the cause such as fever, chest pain, heart failure ... If idiopathic, due to sympathomimetic should use beta-blockers.

Sinus delay:

When there are symptoms should use Atropine should not use Isoproterenol. If prolonged, a pacemaker should be inserted.

Paroxysmal supraventricular tachycardia:

Use vagal stimulation if unresponsive to adenosine, verapamil, beta-bloquant or digoxin in which adenosine is the first choice. If the hemodynamic disturbance is severe, an electric shock should be given.

Atrial fibrillation:

If the response is rapid, with severe hemodynamic instability, cardioversion should be done with an electric shock. If hemodynamically stable, many drugs can be selected: intravenous diltiazem, verapamil, betabloquant, or digoxin to control the ventricular rate.

Complete atrioventricular block:

Need a pacemaker.

Heart failure:

Treatment is similar to another heart failure including diuretics, nitrates, ACE inhibitors, digoxin, and dobutamine, but digoxin is not as effective as in other heart failures because it does not increase myocardial contractility much.

Cardiogenic shock: The cause of death is about 85-90% high due to myocardial infarction (#40% of left ventricular mass) causing left heart failure. Treat as for other cases of cardiogenic shock. Oxygen, raising blood pressure with dobutamine, dopamine, fluid replacement if blood volume is reduced.

Other drugs

Sedative and anti-constipation.


Day 1: Stay in bed.

Day 2: Stay still in bed but move your limbs gently

Day 3: Can sit up

Day 4: Can walk a few steps next to the bed but not strenuous.

After 1 week, you can resume normal activities but do not exert yourself or drive.

Patients can return to normal work when maximal stress testing is achieved (>2 months before stress testing is performed).


Depends on many factors:

Location: left ventricular myocardial infarction has a higher mortality rate than right ventricular myocardial infarction

The larger the infarct area, the higher the mortality rate.

Stage: The mortality rate decreases with the number of sick days


Heart failure: can be based on KILLIP table.

I: No pulmonary congestion and shock, mortality < 5%.

II: Mild pulmonary congestion, possibly with T3 gallop.

III: Pulmonary edema due to acute left heart failure or acute mitral regurgitation # 35-45% mortality.

IV: Cardiogenic shock, mortality #80%.

Heart rhythm disturbances.

Other complications.


Treating risk factors and getting regular exercise is best.

Long-term aspirin use (use clopidogrel if the patient has a contraindication to aspirin).

Beta-blockers: reduce the rate of recurrent myocardial infarction and mortality.

ACE inhibitors: reduce post-infarction mortality and improve left heart function

Regulate dyslipidemia, blood sugar, hypertension.