Coronary Work Flashcards
how to calculate cardial consumption?
multiply the flow of blood thru the tissue by the difference in oxygen concentration between the arteries and veins
list 5 factors that increase mycardial oxygen consumption
- increased heart rate
- increased basal metabolism
- increased stroke volume
- increased ventricular wall tension
- contractile state
What are some ways to measure cardiac performance which one is best?
- tension developed
- pressure developed
- stroke volume
- stroke work- actually used
what are the two ways to increase stroke work?
increase pressure generated and increase volume output
what is the most efficient way to increase stroke work? why?
increasing the stroke volume. d/t laplaces law, T= Pr/2w. doubling volume will only increase r by 1.25 times, so it is less expensive than doubling pressure
what are 5 local regulators of vascular smooth muscle?
all of the following cause dilation:
- decreased o2
- increased co2
- increased H
- increase adenosine
- increased K
how can the sympathetic and parasympathetic nervous system affect smooth muscle indirectly?
sympathetic innervation can increase heart rate, CO, SV, and contractility- all which are an increased performance and thus will require increased VO2. this is sensed via local regulators
parasympathetic- opposite except it lowers heart rate
why does coronary flow fluctuate between systole and diastole?
during contraction (systole), the vessels themselves contract and blood cannot flow thru
when is coronary flow highest? lowest?
highest during diastole. lowest during isovolumetric contraction (systole)
Why does blood flow need to increase for the heart to do more work?
the heart is very efficient at extracting oxygen from the blood at rest. Thus, there is no ability for it to increase oxygen consumption w/o increasing the amount of blood to the tissue
