What Causes a Myocardial Infarction?

Myocardial infarction (MI), commonly known as a heart attack, is a prevalent acute cardiovascular disease. It primarily results from occlusion of the major coronary arteries supplying blood to the heart, leading to interruption of blood flow and subsequent ischemic necrosis of myocardial tissue. MI falls under the umbrella of acute coronary syndrome (ACS). So, what causes myocardial infarction? The following section addresses this question.

Causes of Myocardial Infarction

1. Coronary Artery Atherosclerosis

Unhealthy dietary habits and other factors can increase blood viscosity within the coronary arteries—vessels that supply oxygenated blood to the heart—leading to formation of atherosclerotic plaques adhering to the arterial wall. When these plaques grow excessively large and become unstable, they are prone to rupture under certain triggering conditions. Rupture may be followed by hemorrhage and intraluminal thrombus formation, ultimately resulting in complete arterial occlusion. Consequently, myocardial cells are deprived of their blood supply, causing myocardial ischemia and eventual myocardial cell necrosis.

2. Non-Atherosclerotic Causes

These include coronary artery embolism, aortic dissection involving the coronary ostia, coronary arteritis, and congenital coronary artery anomalies—all of which may precipitate myocardial infarction. Additionally, certain systemic conditions or clinical scenarios may contribute—for example, shock, dehydration, hemorrhage, major surgery, or severe arrhythmias—resulting in an abrupt decline in cardiac output and a consequent sharp reduction in coronary perfusion. Furthermore, consuming a large meal—particularly one rich in fats—can elevate serum lipid levels and blood viscosity, thereby increasing the risk of MI.

Knowledge Extension: Symptoms of Mild Myocardial Infarction

1. Crushing Chest Pain

Crushing chest pain occurring during rest or at night may signal an impending myocardial infarction. Many young adults, due to occupational stress and chronic sleep deprivation, are increasingly susceptible to sudden coronary occlusion, potentially leading to MI—or even sudden cardiac death. Fever typically develops within 1–2 days post-infarction, usually peaking around 38°C (rarely exceeding 39°C) and lasting approximately one week. Therefore, avoiding late-night work and maintaining a balanced schedule between work and rest is essential.

2. Systemic Symptoms

Patients may exhibit pallor, hypotension, altered mental status, or even loss of consciousness. If diabetes mellitus and stroke have been ruled out, these manifestations may indicate early-stage myocardial infarction. Moreover, classic local signs—including low-grade fever, tachycardia, leukocytosis, and elevated erythrocyte sedimentation rate—are attributable to systemic absorption of necrotic tissue. Approximately 20% of patients develop cardiogenic shock, most commonly within hours to one week after symptom onset.

The above outlines the primary etiologies of myocardial infarction. We hope this information proves helpful to you.