Myocardial Infarction & Reperfusion Injury

Myocardial infarction definition

Heart attack due to interrupted blood supply

Ischemia

Reduced blood flow and oxygen delivery

Stroke

Brain ischemia due to blocked blood supply

Anaerobic glycolysis

Only ATP source during ischemia

Phosphocreatine depletion

Rapid during ischemia

Glycogen depletion

Rapid during ischemia

Ion pump failure

ATP depletion → Na+/K+ pump failure

Cell swelling

Osmotic imbalance due to ion pump failure

Membrane permeability

Increases during swelling → leakage of cell contents

Cardiac troponins

Released during MI; diagnostic markers

Lactic acidosis

Due to anaerobic glycolysis

Lysosomal enzyme release

Low pH activates lysosomal hydrolases → cell death

Reperfusion injury

Damage caused by reoxygenation after ischemia

Electron transport saturation

ETC becomes fully reduced during ischemia

ROS burst

Massive reactive oxygen species generated upon reoxygenation

ROS damage

Oxidizes lipids, proteins, DNA → cell death

Antioxidant therapy

Used to mitigate reperfusion injury

Inflammation in reperfusion

Endothelial activation increases permeability

Adhesion molecules

ICAM‑1, VCAM‑1, E‑selectin promote leukocyte infiltration

Neutrophil toxicity

Secrete proteases and generate ROS

Innate immunity role

Toll‑like receptors, complement, mannose‑binding lectin contribute to injury

Cell‑mediated immunity

T‑cells and macrophages involved in reperfusion damage