Coronary Artery Disease-Wendt Flashcards
What is preload?
The amount of blood left in the ventricle after contraction
How do you decrease preload?
Dilating veins (CCBs, nitrates)
What is afterload?
Amount of pressure felt in the ventricle as the heart is contracting
How do you decrease afterload?
Dilate arteries (beta blockers)
What causes angina in Printzmetal’s variant angina?
Vasospasm causes supply ischemia
What causes angina in Chronic Stable angina?
Fixed stenosis of artery causes demand ischemia
What causes angina in Unstable angina?
A thrombus (possibly from a ruptured plaque cap) completely occludes a vessel and causes supply ischemia.
How do nitrates lead to relaxation of vessels?
- NO diffuses into smooth muscle cell and binds to soluble guanylate cyclase.
- cGMP is made and activates PKG
- PKG activates myosin light chain phosphatase, relaxation of muscle.
How do people develop tolerance and how do we prevent this?
ALDH is used to pluck off the NO from the organic nitrate. New ALDH protien must be made.
We prevent this by having a nitrate-free period for about 10 hours/day.
How does the influx of calcium cause contraction?
Calcium binds to calmodulin, which then induces Myosin Light Chain Kinase. This leads to contraction.
How do beta blockers work?
Block binding of NE to heart beta receptors. Leads to decreased heart contraction strength and speed of contraction. This decreases oxygen use and increase perfusion.
How does the activity of protein kinase A differ in vascular smooth muscle cells and cardiac myocytes?
Although PKA is the result of production of cAMP in both cell types, in vascular smooth muscle PKA leads to inhibition of myosin light chain kinase and relaxation, while in cardiac myocytes it phosphorylates calcium channels and allows for an influx of calcium. This leads to contraction.
Which beta blockers are cardioselective?
atenolol, acebutolol, metoprolol
What is reflex tachycardia and how can we prevent it?
Due to a decrease in blood pressure (nitrates, CCBs), the body compensates by increasing heart rate. We can prevent this by using nitrates/CCBs (not verapamil because that causes a decrease in HR) in combination with beta blockers.
