Acute Myocardial Infarction Acute myocardial infarction refers to a potentially life-threatening acute condition within the spectrum of acute coronary syndromes, where the heart muscle undergoes necrosis due to an acute blockage in the coronary arteries, leading to impaired cardiac function as a result of inadequate blood supply.

Acute myocardial infarction refers to a potentially life-threatening acute condition in which the heart muscle undergoes necrosis due to acute blockage of the coronary artery, leading to impaired heart function. It falls under the category of acute coronary syndromes.

According to the globally unified definition of myocardial infarction, acute myocardial infarction can be classified into 5 types.

Type 1

Acute myocardial infarction occurring due to the formation of secondary thrombus following plaque rupture, erosion, or fissuring on the basis of coronary artery plaque.

Elevation or decrease of cardiac muscle troponin, exceeding the upper limit of normal at least once, along with evidence of myocardial ischemia symptoms, new electrocardiographic changes, imaging evidence of myocardial loss or wall motion abnormality due to ischemia, or thrombus indicated by coronary angiography.

Type 2

Elevation or decrease of cardiac muscle troponin, exceeding the upper limit of normal at least once, due to an imbalance between myocardial oxygen demand and supply unrelated to coronary artery thrombosis, along with evidence of myocardial ischemia symptoms, abnormal electrocardiographic changes, or imaging evidence of myocardial loss or wall motion abnormality due to ischemia.

Type 3

Cardiac arrest of cardiac origin. Evidence of pre-existing myocardial ischemia or electrocardiographic changes in patients who did not have serum samples available.

Type 4

Type 4a

Myocardial infarction related to percutaneous coronary intervention.

Significantly elevated cardiac muscle troponin within 48 hours after percutaneous coronary intervention and evidence of myocardial ischemia symptoms, abnormal electrocardiogram, imaging evidence of myocardial loss or wall motion abnormality due to ischemia, or evidence from coronary angiography.

Type 4b

Thrombus formation within the stent after percutaneous coronary intervention.

Type 4c

Renarrowing of the stent lumen after percutaneous coronary intervention.

Type 5

Patients who have undergone coronary artery bypass grafting, experiencing a significant increase in cardiac muscle troponin within 48 hours after the procedure, along with evidence of abnormal electrocardiogram, coronary angiography indicating new occlusion of the bypass graft or native coronary artery, or evidence of myocardial loss or wall motion abnormality due to ischemia.

In summary, for patients who have not previously experienced acute myocardial infarction, if the abnormality of cardiac muscle troponin meets the dynamic changes of myocardial infarction and there is clear evidence of thrombotic occlusion of the coronary artery, it is classified as Type 1. If the abnormality of cardiac muscle troponin meets the dynamic changes of myocardial infarction and excludes thrombotic coronary artery obstruction, it is classified as Type 2.

Patients who have undergone percutaneous coronary intervention are classified as Type 4, and based on the occurrence of restenosis within the stent, they are further categorized into 3 subtypes. Patients who have undergone coronary artery bypass grafting belong to Type 5.

The basic cause of acute myocardial infarction is the obstruction of the heart's own blood supply channels for various reasons, leading to myocardial necrosis due to the lack of blood supply. Therefore, the causes of acute myocardial infarction mainly manifest in the following three aspects:

Decreased blood perfusion within the heart

Various reasons lead to reduced blood supply to certain branches of the coronary artery, resulting in insufficient myocardial blood supply, leading to an imbalance between myocardial oxygen supply and demand.

Common causes of reduced perfusion include coronary artery atherosclerosis, coronary artery spasm, microcirculatory dysfunction, coronary artery embolism, and coronary artery dissection.

Inadequate myocardial oxygen supply

Apart from insufficient blood perfusion, slow arrhythmias, respiratory failure, severe anemia, hypotension, shock, and other conditions can also cause inadequate myocardial oxygen supply. If myocardial hypoxia is severe, the hypoxic area may be damaged and undergo necrosis.

Increased myocardial oxygen consumption

Conditions such as sustained rapid arrhythmias, severe hypertension, and others can lead to myocardial consumption exceeding supply, resulting in myocardial damage due to overwork.

The typical symptoms of this condition include pain or a sense of pressure in the precordial region. The pain or pressure is mainly felt behind the sternum and can radiate to the lower left side, upper abdomen, left shoulder, back, and even to the mouth and head in some patients. It can also be felt in the upper left limb in some cases.

The nature of the pain is often described as "pressure, constriction, or heaviness" in the precordial region. Some patients may not feel significant discomfort in the chest but may experience dull pain or discomfort in other areas outside the chest.

The duration of the pain is typically prolonged, often exceeding 30 minutes, without a distinct peak, and resting or using medications like nitroglycerin does not quickly alleviate the symptoms.

Medication adherence

Medication should be taken according to the doctor's prescription, and the dosage should be adjusted as advised by the doctor.

For patients with chronic conditions such as diabetes, hyperlipidemia, renal insufficiency, etc., adherence to lifelong medication is crucial, and medications should be taken strictly as prescribed.

For patients with conditions such as hypertension, coronary artery atherosclerosis, arrhythmias, heart failure, etc., medications should not be adjusted or discontinued without medical advice, even in the absence of obvious symptoms.

Moderate exercise

Engage in moderate daily exercise, gradually increasing activity levels. Start with lying flat in bed, then progress to sitting, standing with assistance, and eventually walking longer distances.

Maintain regular daily routines

Avoid staying up late. Pay attention to weather changes, adjust clothing as necessary, and avoid getting chilled.

Family support

Regularly communicate with the patient, provide emotional support, and avoid significant emotional fluctuations in the patient.

Rest

During the acute phase of the condition within 12 hours of onset, the patient should be strictly bedridden, and family members should avoid disturbing their sleep excessively.

Exercise

If there are no complications, the patient can engage in light upper limb exercises in bed 24 hours after the onset, and if the condition is stable, the patient can stand briefly at the bedside 72 hours after the onset, gradually transitioning to walking.

Diet

Consume a light and easily digestible, low-fat diet to control blood lipids and delay the progression of coronary artery atherosclerosis. For patients with hypertension and diabetes, blood sugar should also be controlled, and a low-salt diet should be followed.

Emphasize the consumption of plant-based foods, such as the Mediterranean diet, including fruits, vegetables, whole grains, legumes, and nuts, while reducing the intake of saturated fats, cholesterol, and sodium, as it helps in controlling weight, blood pressure, and cholesterol levels.

Dietary recommendations

Consuming fish once or twice a week is beneficial;

Eat more fruits, vegetables, whole grains, legumes, and nuts.

Acute myocardial infarction is a disease caused by various factors leading to the blockage of the coronary artery and subsequent myocardial ischemic necrosis. The occurrence of this disease is, to some extent, the result of many chronic diseases rather than the cause. Actively treating existing chronic diseases is an important means of preventing this condition.

Coronary artery atherosclerosis is an important prerequisite for the occurrence of acute myocardial infarction. After the occurrence of coronary artery atherosclerosis, the ability of the coronary artery to contract and dilate decreases. When a thrombus, detached plaque, etc., obstructs the blood vessels, the heart's ability to dilate the coronary arteries and ensure branch blood supply decreases, weakening the ability to cope with the disease and affecting prognosis.

Therefore, maintaining the elasticity of the coronary artery blood vessels and preventing the formation of blood clots and detached plaques are key points in preventing this condition.

Quit smoking

Cigarettes contain various toxic substances that damage the vascular endothelium with long-term smoking, reducing vascular elasticity.

Low-fat diet

In patients with elevated blood lipids, excess fat adheres to the vascular wall, causing vascular wall hardening and reduced elasticity. In patients with a hypercoagulable state, blood vessels are prone to damage and clot formation after impact.

Weather awareness

Abnormal weather can cause vascular spasm and constriction, leading to a sudden decrease in coronary artery blood supply. Clothing should be adjusted promptly based on weather changes.

Emotional control

Emotional fluctuations can lead to uncontrolled vasoconstriction nerve activity, causing prolonged vasoconstriction and myocardial ischemia. Avoiding excessive emotional fluctuations is important.