Heart Pump Flashcards
What is ejection fraction and how is it calculated?
measure of volume of blood the left heart pumps after each contraction
- EF= SV/EDV
where SV= EDV-ESV
How does one calculate pulse pressure?
Systolic pressure minus the diastolic pressure.
- 120/80 gives us 120-80 and a pulse pressure of 40mmHg
Which valves are closing creating the “lub” of the heart sounds? When does this happen?
AV valves (mitral and tricuspid) -end diastole
Which valves are closing creating the “dub” of the heart sounds? When does this happen?
Semilunar valves (aortic and pulmonary) - End of systole
What is the equation for Cardiac output?
Co= HR*SV
- thus call changes in CO must come from SV or HR
- parasympathetic and sympathetics have immediate effects (within 1 beat)
- Phase 4 for HR is affected.
What is preload? and what are its surrogates?
End diastolic Pressure/ Volume
- EDV and arterial pressure
An increase in preload will do what 2 things?
- increase initial muscle fiber length and thus increase extent of shortening
- Increase end diastolic volume and stroke volume
What is after load? and what is it surrogate?
Active tension placed on cardiac muscle cells during contraction
- mean arterial pressure (MAP= DP+1/3PP)
- or MAP= 2/3 DP + 1/3 SP
- because heart is in diastole 2/3 of the time
What will the affects of after load be?
- Negative effects on cell shortening
- Normal: after load held constant and thus minimal effects on SV
- Leads to decrease of SV from HTN/Aortic valve obstruction
What is the relationship between fiber shortening and contractibility?
An increase in cell shortening leads to an increase there of contractibility
How does SNS or NE lead to increase contractibility?
Increase fiber shortening
- upward and left shift of length-tension curve
What does SNS or NE do the SV?
Increases it because it increases Contractibility through more shortening which is related to decreased ESV!
How does innervation of SNS effect the CO, HR, SV and pressure?
Increase the CO, HR and SV
While pressure remains the same
What receptor does NE bind to on the heart?
Beta- 1 Andrenergic
What positive effects does NE have?
- Chronotropic
- Dromotropic
- Inotropic
- Lusitropic
What does positive chronotropic effect mean?
Activated funny-current in SA node via increase of Na and Ca Permeablity while keeping K about the same. Thus increases likelihood of AP
What is a positive dromotropic effect?
Increase AP conduction (mainly of AV node)
- increases Gap Junctions conductivity
What is a positive inotropic effect?
Increase in cardiac contractibility.
- increase in Ca current and Ca release from SR
What is a positive lusitropic effect?
increase cardiac relaxation
- increase CA uptake by SR
- basically increase turnover for next contraction to compensate for increase HR
What is another way to have a positive lusitropic effect?
decrease AP duration by inducing early activation of K current for faster repolarization
What is the primary source of fuel for the heart in adults, children and CHF patients?
ATP 60-90%
- Fatty acids
- Glucose and lactate
- Glucose
The heart relies on what sort of respiration?
Aerobic meaning loads of mitochondria
- only anaerobic can make enough energy to serve the heart for a few minutes
What is the percent of ATP used by basal metabolism and muscle contraction?
25 and 75% respectively
What is so costly of the muscle contraction?
isovolumetric contraction 50%
- heavily depends on afterload
What would cause your heart to expend more energy by an increase in afterload?
HTN and Aortic valve obstruction
