Pathophysiology of Ischemia/Infarction

Question 1

List types of hypoxia and their causes

Answer 1

Hypoxic - inadequate PaO2, can be caused by low inspired O2, inadequate ventilation, reduced gas transfer - i.e. emphysema, intersitial lung disease, pneumonia
Stagnant - shock, occlusion of vessels i.e. atheroma, tumour pressure
Anaemic
Cytotoxic - PaO2 is fine, hypoxia caused at tissue level e.g. poison.

Question 2

Outline pathogenesis of myocardial infarction

Answer 2

Ischemia causes inadequate O2 and nutrient supply

Drop in ATP conc. Cells begin to respire by anaerobic metabolism, producing lactic acid etc reducing pH of cells - Begins within seconds

Loss of myocardial contractility