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Questions and Answers
What equation is used to calculate cardiac output?
What equation is used to calculate cardiac output?
What is the normal value of ejection fraction?
What is the normal value of ejection fraction?
Which factor influences stroke volume directly?
Which factor influences stroke volume directly?
If a ventricle has an end diastolic volume of 120 ml and an end systolic volume of 45 ml, what is the stroke volume?
If a ventricle has an end diastolic volume of 120 ml and an end systolic volume of 45 ml, what is the stroke volume?
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What does the Frank-Starling principle state?
What does the Frank-Starling principle state?
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What is cardiac reserve?
What is cardiac reserve?
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Which of the following correctly defines preload?
Which of the following correctly defines preload?
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How is cardiac output expressed?
How is cardiac output expressed?
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What is cardiac output?
What is cardiac output?
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The equation for cardiac output is CO = SV x _____.
The equation for cardiac output is CO = SV x _____.
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What is the normal value of cardiac output?
What is the normal value of cardiac output?
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What is ejection fraction?
What is ejection fraction?
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What is the normal ejection fraction value?
What is the normal ejection fraction value?
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What are the components that determine stroke volume?
What are the components that determine stroke volume?
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Define cardiac reserve.
Define cardiac reserve.
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Calculate cardiac output if HR is 75 beats/min and SV is 70 ml/beat.
Calculate cardiac output if HR is 75 beats/min and SV is 70 ml/beat.
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Study Notes
Cardiac Output
- Defined as the volume of blood pumped by the heart every minute.
- Measured in Litres/minute ( L/min)
- Calculated by multiplying Stroke Volume (SV) by Heart Rate (HR): CO = SV x HR
- Normal cardiac output is approximately 5 L/min.
Cardiac Indices and Values
-
Ejection Fraction (EF): Percentage of blood ejected from the ventricle during each contraction.
- Measured using echocardiography.
- Calculated using the formula: EF = (SV/EDV) * 100% (where SV is Stroke Volume, EDV is End-Diastolic Volume)
- Normal EF is greater than 60%.
-
Stroke Volume (SV): Volume of blood ejected from the ventricle with each heartbeat.
- Calculated by subtracting End-Systolic Volume (ESV) from End-Diastolic Volume (EDV): SV = EDV - ESV.
- End-Diastolic Volume (EDV): Volume of blood in the ventricle at the end of diastole (relaxation).
- End-Systolic Volume (ESV): Volume of blood remaining in the ventricle at the end of systole (contraction).
Factors Affecting Stroke Volume
- Preload: The degree of stretch of the ventricle muscle fibers before contraction.
- Afterload: The resistance the ventricle must overcome to eject blood (arterial pressure).
- Contractility: The intrinsic strength of the ventricle muscle.
Frank-Starling Principle
- The heart pumps more blood with a greater preload (increased EDV), as long as contractility is not depressed.
- This mechanism regulates the heart to maintain a steady cardiac output.
Cardiac Reserve
- Represents the difference between resting cardiac output and maximum cardiac output.
- Represents how much more the heart can pump when needed (e.g., during exercise).
Cardiac Output
- Cardiac output refers to the volume of blood pumped each minute and is expressed by the equation: CO = SV x HR.
- Normal cardiac output is approximately 5 L/min.
- SV represents stroke volume, which is the amount of blood pumped per beat, and HR is the heart rate, or the number of beats per minute.
Ejection Fraction
- Ejection fraction is a measure of the heart's pumping efficiency.
- It is the percentage of blood ejected from the left ventricle with each contraction.
- It is most commonly measured using echocardiography.
- A normal ejection fraction is greater than 60%.
Stroke Volume
- Stroke volume is the amount of blood ejected from the heart with each beat.
- It is determined by three factors: preload, afterload, and contractility.
- Preload: The volume of blood in the ventricle at the end of diastole
- Afterload: The pressure the heart must overcome to eject blood.
- Contractility: The force of contraction of the heart muscle.
- Formula: SV = EDV - ESV.
- EDV: End-diastolic volume, the amount of blood in a ventricle at the end of diastole.
- ESV: End-systolic volume, the amount of blood remaining in a ventricle after contraction.
Cardiac Reserve
- Cardiac reserve is the difference between resting heart output and the maximum achievable cardiac output.
- This represents the ability of the heart to increase its output during exercise or stress.
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Description
Test your knowledge about cardiac output, stroke volume, and ejection fraction. This quiz covers the definitions, calculations, and normal values for various cardiac indices. It's a great resource for students studying cardiovascular physiology.
