CV 8 Flashcards
How much oxygen does the heart usually extract
70-80% extraction
Cannot increase oxygen supply by increasing extraction
Right coronary artery
Travels in right AV groove
Acute marginal branches that feed RA and RV
Posterior descending artery feeds posterior wall
Left coronary artery
Feeds most of septum, LV and LA
Splits into left anterior descending artery and left circumflex artery in AV groove
Left anterior descending artery
Branch of LCA
Extends down anterior ventricular septum towards apex
Coronary perfusion pressure
BP within coronary pressure
When is there maximal flow and perfusion to the LV?
During diastole
What happens to the vasculature during systole?
Heart contracts
Muscle tension compresses the coronary vasculature and obstructs blood flow
Least flow near endocardium
What happens to the vasculature during diastole?
Heart relaxed
No compression so blood can flow freely
Coronary perfusion pressure approximated by…
Aortic diastolic pressure
3 things that effect myocardial metabolic rate
Heart rate
Contractility
Wall stress
What changes to the ST segment do you see during subendocardial ischemia?
ST depression (horizontal depression, downsloping, or T wave inversion)
What changes to the ST segment do you see during transmural ischemia?
ST elevation
Adenosine
Potent vasodilator of VSM
Binds to receptor, decreases Ca entry
Most important metabolic regulator of coronary flow
No oxygen, not enough ATP = more ADP, breaks down into adenosine, can leave muscles and bind causes dilation
3 vasodilators
NO
Prostacyclin (PGI2)
Endothelium-derived hyperpolarizing factor (EDHF)
1 examples of a vasoconstrictor
Endothelin 1
Fixed vessel narrowing
Atherosclerotic plaque narrow vessels and therefore increase resistance to flow
Compensation occurs by downstream dilation due to local metabolic need
Occurs in large arteries where there is a higher chance of turbulence
Endothelial cell dysfunction
Occurs early in atherosclerosis
Impaired release of vasodilators
Attenuated effect of local metabolites
Relative vasoconstriction occurs
What happens to
1. Normal resting flow
2. Maximal flow
at 70% occlusion?
- Normal
2. Low
What happens to
1. Normal resting flow
2. Maximal flow
at 90% occlusion?
- Low
2. Low
Myocardial O2 supply depends on (2)
Arterial O2 content
Coronary blood flow
Myocardial demand depends on (1)
Myocardial metabolic rate
