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Mi

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Mi in heart

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Reading File
I have enough to give a solid overview. Here's a summary of MI (Myocardial Infarction) in the heart:

What is MI?

Myocardial infarction ("heart attack") is necrosis of heart muscle caused by ischemia - the muscle dies because it's cut off from adequate blood/oxygen supply. The 2018 Universal Definition (Thygesen et al.) defines it as the presence of acute myocardial injury (detected by elevated cardiac biomarkers, mainly troponin) in the setting of acute myocardial ischemia (Robbins & Kumar Basic Pathology, p. 467).

Cause (Pathogenesis)

The vast majority of MIs result from acute thrombosis in a coronary artery, typically triggered by:
  1. Rupture or erosion of an atherosclerotic plaque, exposing collagen/necrotic contents to blood
  2. Platelet adhesion and aggregation (releasing thromboxane A2, ADP, serotonin), causing further aggregation and vasospasm
  3. Activation of the coagulation cascade via tissue factor
  4. Rapid growth of the thrombus, which can fully occlude the vessel within minutes
About 10% of MIs occur without occlusive atherosclerosis - instead from coronary vasospasm, embolism (e.g., from atrial fibrillation or valve vegetations), or severe fixed stenosis combined with increased demand (tachycardia, hypertension) causing subendocardial ischemia. Rarer causes include vasculitis, amyloid deposition, or sickle cell disease affecting small intramyocardial arterioles (Robbins & Kumar Basic Pathology, p. 467-468).

Types (per the Fourth Universal Definition)

  • Type 1: Spontaneous MI (plaque rupture/thrombosis)
  • Type 2: MI due to ischemic imbalance (supply-demand mismatch without thrombosis)
  • Type 3: Sudden cardiac death associated with MI
  • Type 4/5: MI related to PCI or CABG procedures
(Sabiston Textbook of Surgery, p. 2839)

Key Diagnostic Features

  • Chest pain (often crushing, radiating to arm/jaw), diaphoresis, dyspnea
  • Elevated cardiac troponins (most sensitive/specific biomarker)
  • ECG changes (ST elevation/depression, Q waves depending on type)
Do you want me to go deeper into any specific angle - e.g., ECG changes, treatment/management, histopathology of infarcted tissue, or complications of MI?
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