August 16, 2009

Ischaemic heart disease (causes and pathophysiology)

Myocardial ischaemic occur when there is imbalance between O2 supply and myocardial and myocardial demand.

Can be due to

1) Mechanical obstruction

- Atheroma

- Thrombosis

- Spasm

- Embolus

- Coronary ostial stenosis

- Coronary arteritis

2) Decrease blood flow of oxygenated blood to myocardium

- Anaemia

- Carboxyhaemoglobulinaemia

- Hypotension leads to decrease coronary perfusion pressure.

3) Increase demand of O2

- Increase cardiac input in thyrotoxicosis

- Myocardial hypertrophy (aortic stenosis@ hypertension)

The most common causes for IHD is Coronary artery disease (CAD) due to coronary atherosclerosis.

Mechanism responsible for thrombosis on plaque

1) Superficial endothelial injury

- Break of endothelial lining

- Platelet adhesion

- Migration of smooth muscle from tunica media to intima

- Formation of form cell

- Thrombus formation.

2) Deep endothelial fissuring

- Advanced plaque with lipid core

- Tearing of plaque cap allows entering of blood from lumen into plaque itself

- Core with lamellar lipid surface, tissue fator produced by amcrophage + exposed collegen highly thrombogenic

- Formation of thrombus and expendation of thrombus

- Thrombus extends into lumen.

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