CV 9 Flashcards
3 general treatments for angina
Organic nitrates (ex: nitroglycerin) Beta blockers Calcium channel blockers
How do organic nitrates work to treat angina?
Cause venodilation
Decreases wall stress and oxygen demand
How do beta blockers work to treat angina?
Beta 1 is on the heart
They affect oxygen demand
Decreasing HR lengthens diastolic time so coronary blood can flow
Reduce contractility of the heart - decrease oxygen demand of the heart muscle
How do calcium channel blockers work to treat angina?
L-type calcium channels
They affect oxygen demand and supply - decrease it
Decreases HR lengthens diastolic time so coronary blood can flow
Cause vessel dilation
Reduce the force of contraction
As ischemic myocardial cells lose K+, what changes?
[K+]out increases
5 major differences between a normal AP and an ischemic AP
Change in resting potential (less negative in ischemic)
Slope of depolarization is more to the right in ischemic
Peak isnt as high
Plateau is lower
Repolarization happens faster
Subendocardial ischemia
When some of the subendocardial cells are ischemic
Resting current in subendocardial ischemia
Current flows from ischemic to healthy cells towards the electrode
Results in a positive deflection during PR interval
PR segment used as baseline so looks as though ST segment is depressed
Depolarized current in subendocardial ischemia
Current flow from healthy to ischemic flow is away from the electrode
Seen as an ST depression
Repolarization current in subendocardial ischemia
May see T wave inversion
Because the subendocardial cells have decreases AP duration, so they repolarize before the subepicardial cells
When would you see
- ST depression
- ST elevation
- Subendocardial ischemia (baseline is actually elevated)
2. Transmural ischemia (baseline is actually depressed)
Transmural ischemia (and what is the current doing)
The entire cardiac wall is ischemic
At rest the current flows away from the electrode so you have depression of PR segment
Looks as if ST segment is elevated
2 causes of atherosclerosis
Fixed vessel narrowing
Endothelial cell dysfunction
What is fixed vessel narrowing
Atherosclerotic plaque narrows vessels and therefore increases resistance to flow
To compensate, there is downstream dilation due to local metabolic need
What is endothelial cell dysfunction
Occurs early in atherosclerosis
Impaired release of vasodilators
Attenuated effect of local metabolites
Relative vasoconstriction occurs
5 changes in activated endothelial cells
Increased permeability Increased inflammatory cytokines Increased leukocyte adhesion molecules Decreased vasodilatory molecules Decreased anti-thrombotic molecules
2 things that cause endothelial dysfunction
Physical stress
Chemical irritants
3 changes in activated smooth muscle cells
Increased inflammatory cytokines
Increased extracellular matrix synthesis
Increased migration and proliferation into subintima
How is a fatty streak formed?
LDL enters intima and is modified
Stimulates leukocyte recruitment
Foam cells are formed from monocytes entering intima and differentiating into macrophages which eat lipoproteins
How is a fibrous atheromatous plaque formed?
Smooth muscle cell migration to intima and proliferation in intima
Smooth muscle increase secretion of ECM
Fibrous cap formed over lipid core
Protrusion into lumen altering diameter
