Myocardial infarction is a condition in which blood flow to the heart muscle is suddenly blocked and the area of muscle, left without oxygen, begins to die. Below — the mechanism of the process, the causes of coronary artery occlusion, and the differences between acute myocardial infarction and angina.
Myocardial Infarction: What It Is
Myocardial infarction, or heart attack, is one of the manifestations of coronary heart disease. Blood suddenly stops flowing to the heart, and with it — oxygen. Without treatment, the muscle dies; with prompt medical attention, the damage can be limited. The condition is life-threatening and requires emergency care in a hospital.
Simple mechanics: the heart is a pump, and the coronary arteries are the pipes that supply the pump itself. While the lumen is clear, the pump works; when a pipe is blocked, the pump keeps working, but its own supply lines are already cut off.
By ECG, a distinction is made between non-ST-segment elevation myocardial infarction (NSTEMI) — the artery is partially blocked — and ST-segment elevation myocardial infarction (STEMI) — the blockage is complete.
What Happens in the Heart During Acute Myocardial Infarction
Cholesterol and other substances accumulate on the inner wall of the artery over years — a plaque forms (atherosclerosis). The plaque can rupture, a thrombus forms around it, and the artery becomes blocked. Part of the myocardium is left without oxygen (ischemia) and dies.
Symptoms: pain or discomfort in the center or left side of the chest — pressure, squeezing, burning; pain radiating to the arm, shoulder, neck, jaw, upper abdomen; shortness of breath; nausea and vomiting; a feeling of fullness resembling heartburn; cold sweat; pale, bluish, or gray skin. Signs may appear and disappear over several hours, be mild, or be absent: a "silent" heart attack is more often experienced by older people and people with diabetes. Women more often report atypical manifestations — pain in the upper back or shoulders, dizziness, unusual fatigue.
Complications: heart failure, life-threatening arrhythmias, cardiac arrest.
Call 103 or 112 immediately if chest pain feels like squeezing or a vise, the pain spreads to the arms, neck, or jaw, breathing is sharply difficult — the person is gasping or cannot speak words, the lips or skin are pale, bluish, or gray, the person has lost consciousness and is not responding normally.
Causes: Why the Coronary Artery Becomes Blocked
The most common cause is atherosclerosis of the coronary arteries. Less common is pronounced coronary artery spasm: it blocks blood flow and can occur in vessels without plaques; possible triggers include drug use, smoking, and severe stress (Takotsubo syndrome, "broken heart syndrome"). Another rare cause is dissection, that is, a tear in the artery wall.
Who Is at Risk
Some factors can be changed, some cannot.
- smoking;
- high blood pressure and high cholesterol levels;
- diabetes mellitus;
- excess weight, lack of physical activity, stress;
- a close relative who has had a heart attack; age, sex, and heredity cannot be changed.
Numbers. In 2020, coronary heart disease affected 126 million people worldwide. The average age of a heart attack is 66 years in men and 72 years in women; STEMI is more common in men. Acute myocardial infarction causes more than 4 million deaths in Europe and Northern Asia; in developed countries it accounts for more than a third of deaths per year; in the USA — every 40 seconds. Over the past 20 years, mortality within 6 months after acute myocardial infarction has decreased.
How Myocardial Infarction Is Diagnosed: ECG and Tests
The main investigations are an electrocardiogram (ECG), which shows signs of an impending heart attack, and a blood test for markers of myocardial damage, primarily troponin. The doctor may then order an echocardiogram to determine whether the heart is damaged, and coronary angiography to see exactly where blood flow is impaired. Other methods are also used: cardiac ultrasound, X-ray, CT, or MRI. The diagnosis is made based on symptoms, tests, and imaging; what specific numbers mean is discussed with the doctor.
How Myocardial Infarction Differs from Angina and Other Conditions
In coronary heart disease, the arteries narrow due to plaques, blood flow decreases, and pain or tightness in the chest occurs — this is angina. In myocardial infarction, the symptoms resemble angina but are, as a rule, more intense. Cardiac arrest is a different condition: the heart stops, the person loses consciousness, and different help is needed. During a myocardial infarction, the heart usually does not stop suddenly, but a myocardial infarction can trigger it.
This material is for reference: it explains the mechanism but does not replace a doctor's consultation — the final decision always rests with the doctor.
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This content is for reference and does not replace a doctor's consultation. Medical disclaimer