Acute Myocardial Infarction

The heart starts to beat before you are born and works without rest for a single moment in your life. The adult heart is a 250-300 g muscle bag that does a tremendous job of delivering about 5 liters of beats at 70 beats per minute, about 30 million liters a year, and about 1.5 billion liters of fresh blood for 60 years. The cardiac muscle that does so much work without rest should be supplied with sufficient energy and oxygen, and the coronary arteries play a role.

Acute myocardial infarction is a disease in which the coronary arteries that supply blood to the heart muscle are suddenly blocked by various causes and cause necrosis in the myocardium.

Structure of the coronary artery

Acute myocardial infarction is the most common cause of hospitalization in developed countries and one of the most common causes of death. The initial mortality rate of myocardial infarction is about 30%, and more than 50% of deaths are known to die before they even go to the hospital. Therapeutic drugs and therapies for acute myocardial infarction have advanced rapidly, and mortality from acute myocardial infarction has also decreased by more than 30%, but still 1 in 25 people die from a year after discharge.

Causes and Risk Factors

1. Causes

1) Atherosclerotic rupture and thrombus formation

The most common cause of acute myocardial infarction is atherosclerosis, the most common cause of which is a complete clogging of the coronary artery due to rupture or cracking of the atherosclerotic plaque in the coronary artery. is.

2) Other risk factors

Coronary artery contraction (spasm), coronary embolism, and coronary artery dissection can cause acute myocardial infarction.

2. Atherosclerosis

Atherosclerosis is a vascular disease in which cholesterol is deposited on the walls of blood vessels, which narrows the diameter (inner diameter) inside the vessels, and causes the blood flow to be disturbed by the narrowed blood vessels. Atherosclerosis (a symptom) develops in the coronary arteries that supply blood to the heart muscle, causing blood vessels to narrow and cause blood flow disorders, causing angina, and when completely blocked, causes myocardial infarction.

1) Progression of Atherosclerosis

In atherosclerosis, the initial thickening of the blood vessels with the deposition of cholesterol in normal blood vessels is called an initial lesion.

After further progress, lipids in the macrophage foam cells form a bubble, and the inner lining builds up to a fairly thick state, which is called a fatty stripe lesion.

Atherosclerosis is a more advanced condition called fibrotic atherosclerosis, in which lipids aggregate and gather at the center of the deposited blood vessels to form the core of large lipids. It is called fibrotic atherosclerosis.

Thereafter, very complex lesions occur, fibrous caps are cracked or ruptured, resulting in vascular thrombus, and if very severely developed, acute myocardial infarction occurs due to complete occlusion. Is called.

At this time, the treatment proceeds to remove the thrombi and heal the fibrous cap, which leads to the recovery phase of fibrotic atherosclerosis.

2) Risk Factors for Atherosclerosis

• Unchangeable risk factors
  • Age: Men≥45 years old, Woman≥55 years old
  • Gender: Man> Female
  • Racial: White> Yellow race
  • Family history: Early family heart disease family history (direct family, male <55 years old, female <65 years old)
• Changeable risk factors
  • Smoking
  • Hyperlipidemia: high LDL cholesterol, low HDL cholesterol
  • High blood pressure
  • Diabetes
  • Obesity
  • Lack of exercise
  • Gout
  • Menopause and Oral Contraceptives
  • Characteristic (Type A)
  • Drinking
  • Others: Patients with chronic renal failure, Radiation therapy for mediastinum, Mental stress

Risk factors for atherosclerosis In addition to the above, many other unknown factors are believed to be involved in the development of atherosclerosis and myocardial infarction. However, even among the known risk factors, it is important to prevent smoking, hyperlipidemia, high blood pressure, and diabetes in particular, as the main risk factors, to prevent the occurrence of myocardial infarction.

3. Progression of myocardial necrosis after coronary artery occlusion

Atherosclerosis develops so severe that myocardial infarction develops when necrosis occurs. The coronary artery is blocked and blood is initially deficient and ischemia occurs. Within 2 to 3 hours, necrosis progresses from the center of myocardial endothelium and gradually progresses to the outer membrane. 24 hours after the coronary artery blockage, the entire myocardium is necrotic and progresses to an irreversible condition.

If the treatment proceeds within 20 minutes after the initial myocardial infarction develops and the blood flows again, it does not progress to myocardial necrosis. Once myocardial infarction occurs due to atherosclerosis, smooth blood flow in the shortest possible time is to prevent minimal damage.

4. Left ventricular remodeling after acute myocardial infarction

If acute myocardial infarction has already occurred, the size and shape thickness of the ventricles may change even if the blood vessels are opened again, and there is a risk of future complications. In particular, the size and pressure of myocardial infarction, the area and extent of blockage will have a major impact on future treatment and treatment.

When the heart is in its original state, it can most effectively pump blood all over the body. Therefore, minimizing left ventricular remodeling with rapid reperfusion treatment and active medication after myocardial infarction is of paramount importance in preserving the function of the heart and in preventing complications from myocardial infarction.

Symptoms and Complications

1. Symptoms

The most common symptom is chest pain. Dull pain may feel tight, crushed, or squeezed, and pain in the middle of the neck or chest is typical. Pain can spread to areas other than the chest, which is common in areas of the body above the navel, such as the left arm, neck, and chin. If you have chest pain that lasts longer than 30 minutes and you sweat, you can strongly suspect acute myocardial infarction.

In addition to chest pain, shortness of breath, confusion of consciousness can occur, and there is no risk of sudden death in 20-30% of patients with myocardial infarction. In particular, immediately after surgery, 고 diabetes, older people occur a lot, in this case can be diagnosed by myocardial perfusion test or exercise-induced test.

1) Findings

(1) Whole body findings

The patient is extremely anxious, fidgety, and sometimes he punches in the middle of his chest. Patients with myocardial infarction may have increased sympathetic nerves and reduced systolic function of the heart, resulting in pale facial sweating and cold hands and feet.

(2) Vital signs

• Pulse pulse: Most of them are normal, and some of them can run fast or slow.
• Tachycardia or bradycardia may occur.
• Blood pressure: It is usually normal, some are slightly elevated, or if the myocardial infarction is large, hypotension or heart shock may occur.
• Temperature: After 4-8 hours of infarction, body temperature may rise slightly, and heat may develop within 1-2 days.
• Breathing: In the early stages, pain and anxiety may increase slightly.

(3) Heart and lung examination

Usually, you can hear normal or heart murmurs.
If the left ventricular dysfunction is accompanied by dysfunction, bullous sound may be audible in the lungs.

2) Laboratory findings

(1) Echocardiogram (ECG) findings

ECG is a very important test for the diagnosis of acute myocardial infarction. Electrocardiograms change over time and help to predict superacute, acute and subacute phases. The most characteristic finding of electrocardiogram is ST-elevation, and in some patients it may only appear as ST-clause drop or T-wave inversion. Electrocardiograms can help predict myocardial infarction and coronary arteries.

(2) Myocardial enzyme test

Myocardial enzymes present in the heart muscle are measured and used to diagnose myocardial infarction. Myocardial and necrosis are increased in blood tests and the size of infarction can be estimated.

(3) Heart ultrasound examination

It is the quickest and most useful test. In patients with myocardial infarction, local disorders of the heart wall can be observed. It helps to determine whether emergency reperfusion therapy should be performed in patients with suspected diagnosis.

(4) cardiac nuclear medicine examination

It can be used to diagnose acute myocardial infarction in some patients.

2. Complications

In patients with acute myocardial infarction, a variety of complications can occur, from briefly observed complications to life-threatening dangerous complications, and it is important to minimize the occurrence of complications through rapid reperfusion therapy and active medication.

1) Arrhythmia

Ventricular tachycardia can cause sudden death from acute myocardial infarction. Ventricular tachycardia, which is associated with myocardial ischemia (lack of blood), can usually occur temporarily within the first 24 hours, and if it occurs after 48 hours, it can be treated with an implantable defibrillator after clinical electrophysiology.

Atrial fibrillation can occur with left ventricular dysfunction and is more likely to cause heart failure.

Atrioventricular conduction blockage can cause severe bradycardia (slow vein) and may require a temporary pacemaker.

Several other minor arrhythmias may occur temporarily.
Rapid coronary reperfusion treatment and beta blocker treatment can minimize the occurrence of arrhythmias.

2) Psychogenic shock

It can also occur within the first few hours of infarction, even early in the hospital. Aggressive treatment also has a high mortality rate of over 70%.

3) Acute mitral regurgitation and acute ventricular septal rupture

It usually occurs between two to four days after myocardial infarction. Sudden shortness of breath occurs during recovery, and should be suspected if blood pressure drops. Emergency surgery is required and mortality is high.

4) Heart failure

This can be caused by a decrease in the systolic function of the heart due to infarction and dilation of the normal myocardium. You must actively take medication to preserve heart function.

Diagnoses

Diagnostic criteria for acute myocardial infarction can be diagnosed when two or more of the following three conditions are present.

• Typical chest pain
• ECG findings (rise of ST segment and change of Q wave)
• Increased serum cardiac marker

If severe chest pain lasts for more than 30 minutes and is accompanied by cold sweating, it is likely that acute myocardial infarction has occurred, so you can promptly visit a hospital emergency room and perform an electrocardiogram test and myocardial enzyme test to make an accurate diagnosis.

Treatments

1. Basic Principles of Treatments of Acute Myocardial Infarction

• Minimizing infarcts by quickly reopening closed coronary arteries.
• Minimized death from arrhythmias because most deaths from arrhythmia occur within 24 hours and more than half of patients occur within the first hour.

2. First Aid for Patients with Acute Myocardial Infarction

• If possible, do not move.
• Do not hesitate to call 119 to a hospital where primary coronary interventions are available.
• Do not use ineffective herbal medicine or waste time in private clinics, pharmacies, and oriental medicine clinics.
• Visiting the hospital as soon as possible after symptoms occur within 6 hours or at least 12 hours will help prevent myocardial necrosis (rotation).

3. General Treatments of Patients with Acute Myocardial Infarction

1) Aspirin

First-dose Medication in Patients with Acute Myocardial Infarction

2) Relief of chest pain

When you arrive at the hospital, sublingual administration of nitroglycerine, intravenous morphine, and intravenous beta-blockers help control chest pain and reduce myocardial oxygen demand. However, nitroglycerine is contraindicated when hypotension or right ventricular infarction or sildenafil (viagra) taken within 24 hours.

3) Anticoagulant therapy

Heparin, platelet aggregation blocker, etc.

4. Reperfusion Therapy in Patients with Acute Myocardial Infarction

1) Thrombolytic release

Acute myocardial infarction is caused by the closure of the coronary arteries by blood clots (blood clots) and can be treated to dissolve blood clots. This is called thrombolysis.

In principle, thrombolytics are given to the patient’s vein within 30 minutes of the emergency room visit. It is important for you to see your doctor as soon as possible after you have symptoms, since treatment will work best for you within one to three hours of your symptoms. Thrombolytic therapy is useful in patients who are present within 3 hours of symptom onset, and the treatment is similar to that of primary coronary angioplasty.

The problem with thrombolytic therapy is currently not used much because of the low success rate of about 60-70%, high recurrence rate (10-15%), and the possibility of serious bleeding.

2) Primary coronary angioplasty

Primary coronary angioplasty is a rapid method of coronary balloon dilatation and stent implantation in acute myocardial infarction patients. It is the best method for reopening closed vessels and has a high re-success rate of 95-99%. It is the most widely used reperfusion treatment.

Primary coronary angioplasty is usually performed within 90 minutes of the patient’s appointment, and the sooner it is done, the better. Primary coronary angioplasty is useful for patients who visited within 12 hours of chest pain, and if chest pain persists after 12 hours. Primary coronary angioplasty within 2-3 hours of chest pain and successful reopening can maintain normal cardiac function without myocardial necrosis.

The recurrence rate was slightly higher (20-30%) when using a standard stent, but to reduce recurrence, the drug-coated stent coated with a drug that inhibited restenosis was reduced to 5-10%. A problem with drug-coated stents can cause blood clots in the stent in very few patients, which is prevented by the treatment of platelet inhibitors aspirin and clopidogrel.

3) Reasons for improvement of coronary reperfusion treatment and improvement measures

Don’t waste time waiting for vague expectations to “be better” after a chest pain or visit a private hospital, pharmacy, or clinic. If your chest pain lasts more than 10 minutes, you should call a 119 ambulance (Step A) and get them to a hospital where primary coronary interventions are available (Step B). In the hospital, an emergency coronary intervention team is always on hand to provide 24 hour emergency procedures and should be promptly performed when the patient comes.

Preventions

1. Medication to prevent recurrence (secondary prevention)

1) Aspirin

• It inhibits platelet activation and prevents the production of blood clots.
• Reduce mortality by 30-50%.
• Must be taken throughout life.

2) Beta blockers

• Suppresses the sympathetic nervous system, reducing myocardium oxygen consumption, inhibiting platelet aggregation and antiarrhythmic effects.
• Reduces risk of death and mortality by 20-50%.
• Even in patients with heart failure, mortality is reduced by 30-40%.

3) Angiotensin converting enzyme inhibitor or angiotensin receptor blocker

• Improves the function of the heart by reducing the back load of the heart.
• Reduce mortality by 20-30%.

4) Statins

• It is a treatment for hyperlipidemia and reduces mortality by 30-50%.
• Stabilizes the arteriosclerosis and reduces the recurrence of myocardial infarction.

As a result, it is very important to have a second prevention with proper medication in patients with acute myocardial infarction. Using all four of these medications can reduce heart disease recurrence by 70% compared to unused patients, so if you do not have contraindications, these four medications must be performed. Patients should visit the hospital regularly to actively control blood pressure, diabetes and hyperlipidemia to minimize recurrence.

2. Life Therapy for Secondary Prevention

• Stop smoking.
• Reduce alcohol to one or two glasses a day.
• Eat foods evenly.
• Reduce fat and eat plenty of vegetables and fish.
• Proper exercise for at least 30 minutes every day.
• Keep your weight and waistline moderate.
• Reduce stress and enjoy a happy life.

Acute myocardial infarction is a fight against time. Your prognosis depends on how quickly you come to the hospital after you have symptoms and how quickly you reopen clogged blood vessels. If you experience chest pain, you should visit a hospital where you can have immediate coronary intervention without delay, and your doctor should diagnose it quickly and perform reperfusion. In addition, once discharged after treatment for acute myocardial infarction, patients should try to prevent recurrence through active medication and lifestyle therapy.

In conclusion, acute myocardial infarction is a frightening disease, but active treatment can maintain a normal life without complications. Therefore, patients who have chest pain or are at high risk of atherosclerosis should be treated and actively managed by a cardiologist.