How does a heart attack occur

A common sense that everyone should know is that there are many arteries distributed around the human heart, and these arteries not only supply blood, but also transfuse blood. But when these arteries become blocked, it can cause a myocardial infarction. Myocardial infarction can damage the blood supply to a person's heart, which seriously affects the normal functioning of the heart. But how does myocardial infarction occur?

Myocardial infarction refers to an acute ischemic heart disease with sudden complete occlusion of the coronary arteries on the basis of coronary artery lesions, a sharp reduction or interruption of coronary blood supply, myocardial ischemia, damage and necrosis, and clinical features such as severe chest pain, fever, white blood cell count, progressive electrocardiogram and dynamic changes in myocardial enzymes. Arrhythmia, shock or heart failure may occur, which is a severe type of coronary heart disease. The underlying lesions are mostly coronary atherosclerosis, and a few are other lesions such as acute coronary embolism.

Causes

The coronary artery is the nutrient blood vessel of the heart. Because it surrounds the atrioventricular groove to form a ring shape, it is worn on the heart like a hat (the ancients called it a crown), hence the name coronary artery. It is the first branch of the human body's aorta, the ascending aorta. It starts from the aortic sinus and divides into the left coronary artery and the right coronary artery. The former is further divided into two larger branches, the anterior descending branch and the circumflex branch. The anterior descending artery, the circumflex artery and the right coronary artery are the three main blood vessels that nourish the heart. The vast majority of myocardial infarctions are caused by coronary atherosclerosis, which begins in childhood and continues to progress. As lipids continue to deposit in the blood vessel walls, the coronary arteries slowly develop lumen narrowing, which can gradually progress to lumen obstruction, leading to reduced blood supply to the myocardium.

However, during the natural formation of atherosclerotic plaques, the instability of lipid plaques may lead to sudden changes, namely plaque rupture, bleeding and thrombosis, which further aggravate the stenosis of the blood vessel lumen, reduce the blood flow to below a certain critical level, or even completely block the lumen, thus blocking the blood flow and causing an imbalance between myocardial oxygen supply and demand. If this imbalance is severe and persistent, it may lead to ischemic damage to the myocardium. When severe ischemia and hypoxia persist for a long time, irreversible necrosis occurs in a large area of ​​the myocardium, which is called myocardial infarction. The myocardium distal to the blocked coronary artery loses its ability to contract and cannot complete the contraction, affecting the pumping function of the heart, especially the left ventricle, and subsequently causing dysfunction of various systems throughout the body, such as the lungs, kidneys, endocrine and blood systems. There are also patients with aortic stenosis and thyrotoxicosis, whose myocardial oxygen demand increases significantly, which may occasionally become the cause of acute myocardial infarction. In cases of severe anemia or carbon monoxide poisoning, the coronary blood oxygen content is significantly reduced, leading to a severe lack of myocardial oxygen demand, which may also be the cause of acute myocardial infarction.

In addition, various types of aortic stenosis, severe aortic valve insufficiency, tachyarrhythmias, and severe hypotension reactions can cause a significant decrease in coronary blood perfusion and can also be the cause of acute myocardial infarction.