Podcast
Questions and Answers
What is the typical unit of measurement for cardiac output?
What is the typical unit of measurement for cardiac output?
- Beats per minute (BPM)
- mmHg/volume/time
- Milliliters per beat (mL/beat)
- Liters per minute (L/min) (correct)
If a patient has an end-diastolic volume (EDV) of 120 ml and an end-systolic volume (ESV) of 50 ml, what is their stroke volume?
If a patient has an end-diastolic volume (EDV) of 120 ml and an end-systolic volume (ESV) of 50 ml, what is their stroke volume?
- 170 ml
- 70 ml (correct)
- 50 ml
- 120 ml
What is the average normal ejection fraction (EF) percentage range in a healthy adult?
What is the average normal ejection fraction (EF) percentage range in a healthy adult?
- 50-63% (correct)
- 30-40%
- 40-50%
- 65-75%
According to the Frank-Starling law, within physiological limits, what happens to the force of contraction of the cardiac muscle as the initial length of the muscle fiber increases?
According to the Frank-Starling law, within physiological limits, what happens to the force of contraction of the cardiac muscle as the initial length of the muscle fiber increases?
Which of the following best describes afterload?
Which of the following best describes afterload?
What effect does increased sympathetic tone typically have on heart rate?
What effect does increased sympathetic tone typically have on heart rate?
Which of the following is directly proportional to venous return?
Which of the following is directly proportional to venous return?
What is the primary effect of the skeletal muscle pump on venous return?
What is the primary effect of the skeletal muscle pump on venous return?
What is the effect of increased afterload on stroke volume, assuming other factors remain constant?
What is the effect of increased afterload on stroke volume, assuming other factors remain constant?
What is the equation for calculating cardiac output (CO)?
What is the equation for calculating cardiac output (CO)?
How does the respiratory pump mechanism aid in venous return?
How does the respiratory pump mechanism aid in venous return?
How would a chronic increase in afterload (e.g., due to hypertension) affect the heart over time?
How would a chronic increase in afterload (e.g., due to hypertension) affect the heart over time?
Which of the following is the most direct determinant of preload?
Which of the following is the most direct determinant of preload?
A patient's cardiac index (CI) is found to be significantly lower than normal. What might this indicate?
A patient's cardiac index (CI) is found to be significantly lower than normal. What might this indicate?
According to the images, what is the approximate normal value for cardiac index in an adult?
According to the images, what is the approximate normal value for cardiac index in an adult?
What is the primary advantage of physiological hypertrophy (e.g., in athletes) compared to pathological hypertrophy?
What is the primary advantage of physiological hypertrophy (e.g., in athletes) compared to pathological hypertrophy?
A patient's blood viscosity increases significantly due to a condition like polycythemia vera. How would this affect cardiac output, assuming all other factors remain constant?
A patient's blood viscosity increases significantly due to a condition like polycythemia vera. How would this affect cardiac output, assuming all other factors remain constant?
If a person transitions from lying down (supine) to standing up quickly, what immediate change helps counteract the effects of gravity on venous return from the lower body?
If a person transitions from lying down (supine) to standing up quickly, what immediate change helps counteract the effects of gravity on venous return from the lower body?
Compared to a resting heart, how would the Frank-Starling curve of a strenuously active heart differ?
Compared to a resting heart, how would the Frank-Starling curve of a strenuously active heart differ?
A hypothetical drug selectively inhibits the venous valves in the legs. What is the MOST LIKELY immediate physiological consequence?
A hypothetical drug selectively inhibits the venous valves in the legs. What is the MOST LIKELY immediate physiological consequence?
Flashcards
Cardiac Output (CO)
Cardiac Output (CO)
The volume of blood pumped by each ventricle per minute, typically 5.5 liters per minute.
Stroke Volume (SV)
Stroke Volume (SV)
The volume of blood pumped by each ventricle per beat, around 75ml per beat.
End Diastolic Volume (EDV)
End Diastolic Volume (EDV)
Volume of blood in the ventricle at the end of diastole, approximately 130ml.
End Systolic Volume (ESV)
End Systolic Volume (ESV)
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Cardiac Index
Cardiac Index
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Ejection Fraction (EF)
Ejection Fraction (EF)
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Preload
Preload
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Afterload
Afterload
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Factors Determining CO
Factors Determining CO
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Pumping Power Influences
Pumping Power Influences
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Frank-Starling Law
Frank-Starling Law
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CO and Venous Return
CO and Venous Return
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Sympathetic Tone Effects
Sympathetic Tone Effects
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CO Relation
CO Relation
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Cardiac Suction Effect Factors
Cardiac Suction Effect Factors
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Venous Return (VR) Equation
Venous Return (VR) Equation
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VR as Cardiac Input
VR as Cardiac Input
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Study Notes
Cardiac Output (CO) Basics
- Cardiac output (CO) is the volume of blood pumped by each ventricle per minute.
- CO is calculated by multiplying heart rate (HR) by stroke volume (SV).
- CO = HR x SV
Determinants of CO - HR and SV
- Heart Rate (HR), End Diastolic Volume (EDV) , End Systolic Volume (ESV), Stroke Volume (SV) are all related
Cardiac Output Volume
- Cardiac output is the volume of blood pumped by each ventricle per minute, and averages 5.5 liters per minute in a healthy individual.
- Stroke volume is the volume of blood pumped by each ventricle per beat, averaging 75 ml per beat.
Stroke Volume (SV) Calculation
- Stroke volume (SV) is determined by subtracting end-systolic volume (ESV) from end-diastolic volume (EDV).
- SV= EDV - ESV
- End diastolic volume (EDV) is the volume of blood present in the ventricle at the end of diastole, typically around 130ml.
- End systolic volume (ESV) is the volume of blood present in the ventricle at the end of systole, averaging 55 ml.
Cardiac Index
- Cardiac index is calculated by dividing cardiac output (CO) by body surface area.
- Cardiac index is normally around 3.2 (l/m)/m² in adults.
- Cardiac index tends to be higher in children and lower in older adults.
Ejection Fraction (EF)
- Ejection fraction (EF) is the ratio between stroke volume (SV) and end-diastolic volume (EDV).
- EF is normally around 58%, with a range of 50-63%.
Factors Determining Cardiac Output
- Pumping capacity of the heart and venous return are key factors.
Factors Related to the Pumping Capacity of the Heart
- Preload, sympathetic tone, and physiological hypertrophy are directly proportional to the pumping power of cardiac muscle.
- Afterload is inversely proportional to the pumping power of cardiac muscle.
Factors Determining Venous Return
- Venous return (VR) is directly proportional to the pressure gradient (MSFP – RAP).
- VR is inversely proportional to resistance to blood flow.
Proportionality of CO
- CO is directly proportional to the pumping power of the cardiac muscle and venous return.
- VR is considered the cardiac input.
Preload
- Preload is the initial length of cardiac muscle just before myocardial contraction.
- Preload depends on venous return, which determines end-diastolic volume (EDV).
Frank-Starling Law
- Within limits, the force and velocity of cardiac muscle contraction is directly proportional to the initial length of contractile muscle fibers.
Afterload
- Afterload is the resistance that the heart faces during systole.
- Afterload depends on aortic impedance, which is affected by aortic blood pressure (ABP), blood viscosity, and atherosclerosis.
Sympathetic Tone Effects
- Sympathetic tone causes generalized vasoconstriction in systemic blood vessels.
- Sympathetic tone stimulates the adrenal medulla to secrete catecholamines.
- On the heart, sympathetic tone increases heart rate (up to 150 BPM) and cardiac contractility (20-25%).
Regulation of Venous Return
- Key factors include venous valves, the cardiac suction effect, skeletal muscle pump, blood volume, respiratory pump, MSFP (Mean Systemic Filling Pressure), and sympathetic vasoconstriction.
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