Symptoms, Complications, and Diagnosis of Acute Myocardial Infarction



Symptoms and Complications



1. Symptoms

The most common symptom is chest pain. A dull pain may feel like squeezing, pressing, or clenching, and pain in the upper abdomen or the center of the chest is typical. The pain can spread beyond the chest, and this radiating pain commonly appears in the left arm, neck, jaw, and other body parts above the navel. If chest pain lasting more than 30 minutes is accompanied by sweating, acute myocardial infarction should be strongly suspected, and immediate hospital visit is necessary.



In addition to chest pain, shortness of breath and confusion may occur, and because 20~30% of myocardial infarction patients do not have chest pain, there is a risk of sudden death. This occurs especially often immediately after surgery, in patients with diabetes, and in older adults. In such cases, diagnosis can be made through myocardial perfusion testing or exercise stress testing.



1. Physical examination findings

(1) General findings

The patient is extremely anxious and restless, and may even pound the center of the chest with a fist. In myocardial infarction patients, sympathetic nervous system activity is increased and the heart’s systolic function is reduced, so the face may appear pale, sweating may occur, and the hands and feet may feel cold.



(2) Vital signs

· Pulse: Most are normal, but some may have a fast or slow pulse. Tachycardia or bradycardia may occur.

· Blood pressure: Usually normal, but in some cases it may be slightly elevated; if the infarct area is large, hypotension or cardiogenic shock may occur.

· Body temperature: After 4-8 hours of infarction, body temperature may rise slightly, and fever may occur within 1-2 days.

· Respiration: In the early stage, it may increase slightly due to pain and anxiety.



(3) Cardiac and lung examination

Usually normal, but a heart murmur may be heard. If heart failure with reduced left ventricular function is present, crackles may be heard on lung auscultation.



2. Laboratory findings

(1) Electrocardiogram findings

The electrocardiogram is a very important test for diagnosing acute myocardial infarction. Electrocardiogram findings change over time and help predict the hyperacute, acute, and subacute phases. The most characteristic finding on the electrocardiogram is ST-segment elevation, and in some patients it may appear only as ST-segment depression or T-wave inversion. The electrocardiogram also helps predict the infarct location and the coronary artery involved.



(2) Myocardial enzyme test

This test is used to diagnose myocardial infarction by measuring myocardial enzymes that are mainly present in the heart muscle. They increase in blood tests when the myocardium becomes necrotic, and the size of the infarction can be estimated.



(3) Echocardiography

This is the fastest and most useful test. In patients with myocardial infarction, regional wall motion abnormalities of the heart can be observed. It helps decide whether emergency reperfusion therapy should be performed in patients whose diagnosis is uncertain.



(4) Cardiac nuclear medicine test

In some patients, it can be used for the diagnosis of acute myocardial infarction.



2. Complications

In patients with acute myocardial infarction, a wide range of complications can occur, from mild, transient complications to life-threatening ones. It is important to minimize the occurrence of complications through rapid reperfusion therapy and active drug treatment.



1. Arrhythmia

Ventricular tachycardia can cause sudden death due to acute myocardial infarction. Ventricular tachycardia is associated with myocardial ischemia (lack of blood flow) and usually occurs temporarily within the first 24 hours. If it occurs after 48 hours, it can be treated with an implantable defibrillator after a clinical electrophysiological study.



Atrial fibrillation may occur in relation to reduced left ventricular function, and the likelihood of heart failure is high. Severe bradycardia (slow pulse) may occur due to atrioventricular conduction block, and in some cases a temporary pacemaker may be needed.



Various other mild arrhythmias may also occur temporarily. Rapid coronary reperfusion therapy and beta-blocker treatment can minimize the occurrence of arrhythmias.



2. Cardiogenic shock

It may occur within the first few hours of infarction and also during the early hospital period. Even with active treatment, it has a high mortality rate of over 70%.



3. Acute mitral regurgitation and acute ventricular septal rupture

These usually occur 2-4 days after myocardial infarction. They should be suspected if sudden shortness of breath and a drop in blood pressure occur during recovery. Emergency surgery is required, and the mortality rate is high.



4. Heart failure

It can occur due to reduced systolic function of the heart caused by expansion of the infarct area and the normal myocardium. Active drug treatment to preserve cardiac function should be provided.



Diagnosis

A diagnosis of acute myocardial infarction can be made when at least two of the following three criteria are present.



① Typical chest pain

② EKG findings (ST-segment elevation and Q-wave changes)

③ Increased serum cardiac markers



If severe chest pain lasts more than 30 minutes and is accompanied by cold sweats, the likelihood of acute myocardial infarction is high, so you should quickly visit a hospital emergency room for an electrocardiogram and myocardial enzyme tests to make an accurate diagnosis.





So far, we have explained the symptoms, complications, and diagnosis of acute myocardial infarction.

In the next part, we will look at the treatment of acute myocardial infarction.





Source: Korea Disease Control and Prevention Agency National Health Information Portal