Flashcards in Ischemia/Reperfusion- Exam 2 Deck (46)
Blood supply problem
What will the EKG show with myocardial ischemia?
Depressed ST segment
Inverted T wave
What causes myocardial ischemia?
Not enough blood
What will the EKG show for myocardial infarction?
Pathologic Q waves; permanently
What is released with myocardial infarction?
What will the EKG show for myocardial injury?
Elevated ST segment
Oxygen Free Radicals
Reactive Oxygen Species (ROS)
Altered O2 molecules created; at XC and reperfusion; reactions add unpaired electrons to outer orbit
5 reactions leading to O2 Radical Formation
1. NADPH + O2 = Superoxide O2-
2. Superoxide Dismutase O2- -> Hydrogen Peroxide H2 O2
3. Hydrogen peroxide + myeloperoxidase= hypochlorite HOCL
4. Hydrogen peroxide + Catalase = O2 + H20
5. Hydrogen peroxide + Fe++ = Hydroxyl Radical OH
How are reactive oxygen species created?
Xanthine oxidase releases in endothelial cells; catalyze: hypoxanthine to xanthine to uric acid
What enzyme is important in purine breakdown path?
Total depletion of O2; complete lack of O2
Lack of oxygen delivered to tissues
Lack of blood supply
Restoration of circulation
Reperfusion; can result in inflammation and oxidative damage through inducing oxidative stress rather than restoration of normal funcion
What abrupt biochemical and metabolic changes occur resulting in reperfusion injury?
Generative of reactive oxygen species
Intracellular calcium overload
Rapid restoration of physiologic pH
What does cell death result from? (related to reperfusion injury)
Opening of mitochondrial permeability transition pore and induction of cardiac myocyte hyper-contraction
What protects the heart from free radicals?
Antioxidant system (electron donators)
What are the three antioxidant system components?
What is the 5' nucleotidase system?
Converts AMP to adenosine
When is full recovery impossible?
If adenosine nucleotide pool <50% full recovery
What are the mediators of lethal reperfusion injury?
too much of a good thing: oxygen-derived free radical formation (reactive oxygen species ROS)
large influx of calcium into the cell
pH moves from acidic to normal- potentiates many of hte changes
What is depleted during ischemia?
Tissue stores of endogenous antioxidants
What factors determine the amount of oxygen free radicals produced?
Severity of ischemic injury
actiavtion and recruitment of neutrophils to myocardium
Level of O2 in the cardioplegic solution
presence of endogenous scavengers and inhibitors