Exam #2: Cardiac Output Flashcards
What is cardiac output?
Heart Rate x Stroke Volume
CO=HR x SV (LVEDV- LVESV)
What are the determinants of cardiac output?
1) Preload
2) Contractility
3) Afterload
4) Heart rate
*1-3= SV 4= HR
Draw the cardiac length-tension curve.
Y= Tension X= Length
Increased length= increased tension
Draw the Frank-Starling Curve.
X= End diastolic volume Y= Intraventricular systolic pressure
Increased EDV= increased developed tension & intraventricular systolic pressure
Pathophysiology of heart failure.
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What is the effect of decreased HR on Frank-Starling curve?
Decreased rate= increased EDV
Increased SV
CO maintained
What is the effect of increased HR on Frank-Starling curve?
Increased HR= decreased EDV= decreased SV
CO maintained
Draw the left ventricular volume & pressure curve.
N/A
A= mitral valve filling (ESV) B= mitral valve closed (EDV) C= Isovolumic contraction & aortic semilunar valve opens D= Blood ejected into periphery & aortic valve closes
What is preload?
End diastolic pressure when ventricle has become filled
- Venous return
What is afterload?
Aortic pressure
- TPR
- Pressure the heart has to pump into/against
Draw the Frank-Starling Curve on Pressure-Volume.
N/A
What is the effect of increased preload on SV?
Increased SV
Draw the Effect of Preload.
N/A
What is the effect of afterload on SV?
Decreased SV
Draw the effect of afterload on SV.
N/A
Draw the Sarnoff curve of the heart.
N/A
Contraction curve
Draw the effect of contractility with pressure-volume curve.
N/A
What does a positive ionotropic agent do to the afterload curve?
Shifts the afterload curve upward
What will a decrease in contractility to do to afterload curve?
Shift downward
What is the difference between a systolic dysfunction & a diastolic dysfunction?
Systolic= unable to contract efficiently
Diastolic= unable to relax
What is the Frank-Starling’s law of the heart?
Increased stretch of the sinus node, increases heart rate
Draw the venous return curve. What happens when there is a sudden drop in venous return/ volume?
Decreased right atrial pressure & decreased systemic filling pressure
Draw the venous return curve. What happens when there is a change in TPR i.e. vasodilation or vasoconstriction?
Changes in ateriolar resistance change what is coming back to the heart, but NOT overall pressure of systemic filling
Draw cardiac function curves.
N/A
Draw the cardiac function curves with autonomic control: maximal SNS, normal, sympathetic withdrawal, & PNS.
N/A
How the sympathetic input effect CO?
Increases the force & rate of contraction
How does SNS increase the force of cardiac contraction?
- Increased slope of phase 4 depolarization in nodal cells= increased HR
- Alteration of Ca++ permeability (more inward)= increased contraction
- Glyogenolysis= breakdown of glycogen (energy)
BOTH= large increase in CO
*Note that the SNS innervates the SA/AV nodes & cardiac myocytes
How does parasympathetic input effect CO?
Massive decrease in heart rate
Physiologically, what happens during systole with acute exercise because of sympathetic activity?
- Increased glycogenolysus leads to energy mobilization & enhanced substrate for contraction
- Increase contractility via increasing Ca++ permeability during Phase 2
- Increased heart rate
All leads to an increase in CO
Physiologically, what happens during diastole with acute exercise because of sympathetic activity?
- Increased HR leads to decreased filling time
- Changes in Ca++ permeability go BOTH ways i.e. enhanced efflux (Na+ -Ca++ exchanger) & sequestration
Shorter relaxation & filling time but increased contractility & efficiency
Draw the cardiac output & venous return curves.
N/A
What is the equilibrium point of the cardiac output and venous return curves?
Right atrial pressure
Draw the change that occurs with cardiac output and venous return with increases SNS innervation.
N/A
How is cardiac output measured?
Fick Principle
What is the Fick Principle?
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What is the Indicator Dilution Method used to measure cardiac output?
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List some factors that increase CO.
Reduced TPR
- AV shunt
- Hyperthyroidism
- Anemia
List some factors that decrease CO.
Heart damage
- Ischemia
- Valvular disease
Decreased blood volume
Acute venous dilation or obstruction
Decreased tissue mass or tissue metabolism
