EXAM 1: Lecture 4 Flashcards
What is Preload?
The amount of pressure available to fill the heart with blood.
Preload is a key determinant of heart filling; high preload allows for more blood to fill the heart, while low preload limits filling.
What does an increased preload do to stroke volume?
Increases stroke volume.
An increased preload raises the left ventricular end diastolic volume, resulting in greater stroke volume.
What is Afterload?
The amount of pressure the heart has to pump against, specifically the pressure on the outside of the aortic valve.
Afterload is essentially the blood pressure that the heart must overcome to eject blood.
How does increased afterload affect the heart’s pumping ability?
Makes it more difficult for the heart to pump blood out.
An increase in afterload leads to longer times in phase 2 and less time in phase 3, decreasing overall ejection volume.
What is Contractility?
A change in stroke volume when preload and afterload are held constant.
Contractility reflects the strength of the heart’s contraction.
What happens to stroke volume with increased contractility?
Increases stroke volume and decreases left ventricular end systolic volume.
Increased contractility allows for more efficient ejection of blood from the heart.
What is Mitral Regurgitation?
A leaky valve allowing blood to flow backward into the atria.
This condition results in increased left ventricular end diastolic volume and can lead to stretching of the left ventricle.
What effect does decreased preload have on stroke volume?
Decreases stroke volume.
A decrease in preload reduces left ventricular end diastolic volume, leading to lower stroke volume.
What is Aortic Insufficiency?
A leaky aortic valve causing retrograde blood movement when the valve is closed.
This results in increased left ventricular end diastolic volume and can significantly increase stroke volume.
What is the relationship between afterload and heart rate?
Increased afterload can lead to increased heart rate.
The heart compensates for decreased stroke volume by increasing the number of beats per minute.
What is Aortic Stenosis?
A condition where the aortic valve does not open fully, creating high resistance to blood flow.
This condition is treated as a high afterload issue and reduces stroke volume while requiring an increased heart rate to maintain cardiac output.
What happens during decreased afterload?
Easier pumping for the heart, increased stroke volume, and decreased heart rate.
Decreased afterload shortens phase 2 and extends phase 3, allowing for better ejection of blood.
What are the effects of increased preload on left ventricular pressure?
Increases left ventricular pressure.
Increased preload also raises left ventricular end diastolic volume and systolic blood pressure.
Fill in the blank: An increased afterload leads to a _______ in stroke volume.
Decrease.
Higher afterload makes it harder for the heart to eject blood, thus reducing stroke volume.
True or False: Mitral stenosis results in increased stroke volume.
False.
Mitral stenosis causes decreased filling and reduced stroke volume.
What compensatory mechanisms may the body use in response to mitral valve stenosis?
Increase preload, increase atrial pressure, increase blood volume, increase PSF.
These mechanisms aim to raise pressures in the system to compensate for reduced stroke volume.
What is the normal diastolic pressure in the aorta?
80mmHg.
This pressure is crucial for the heart to overcome in order to open the aortic valve during systole.
What happens to left ventricular end systolic volume with decreased contractility?
Increases from 50mL to 75mL.
Decreased contractility leads to less effective ejection of blood from the ventricle.
How does aortic valve stenosis affect pulse pressure?
Leads to a narrow pulse pressure of about 20mmHg.
This is a hallmark characteristic of severe aortic stenosis.
What is the impact of increased afterload on the phases of the cardiac cycle?
Increased time in phase 2, decreased time in phase 3.
This results in decreased volume ejected and increased end systolic volume.
What happens to stroke volume and end systolic volume during decreased afterload?
Increased stroke volume, decreased end systolic volume
Decreased afterload makes it easier for the heart to pump and reduces the energy expenditure.
What is the effect of increased contractility on stroke volume and cardiac output?
Increased stroke volume, increased cardiac output
Increased strength of contraction results in a steeper contractility slope.
What are negative inotropes and give examples?
Medications that decrease contractility, e.g., beta blockers, calcium channel blockers
Negative inotropes reduce the heart’s ability to contract.
What characterizes mitral regurgitation?
Leaky mitral valve causing backflow into left atrium
Results in increased left ventricular end diastolic volume and stroke volume.
What are compensatory factors for mitral valve stenosis?
- Increased heart rate
- Increased preload
- Increased right atrial pressure
- Increased filling volume
These factors help maintain cardiac output despite decreased stroke volume.
What is aortic insufficiency?
Leaky aortic valve causing backflow into the ventricle
Increases left ventricular end diastolic volume and decreases ventricular pressure.
What is the effect of aortic stenosis on left ventricular pressure?
Increased left ventricular pressure
Aortic stenosis creates a high resistance to blood ejection.
Fill in the blank: The formula for ejection fraction is __________.
Stroke volume/end diastolic volume or (end diastolic volume – end systolic volume) / end diastolic volume.
What happens to ejection fraction in a heart with regurgitation?
Gives a falsely high ejection fraction number
Regurgitation affects the accuracy of the ejection fraction measurement.
What is the effect of untreated heart failure on end systolic volume?
Higher end systolic volume compared to normal
Results from reduced contractility and leads to compensatory increased heart rate.
How does treating heart failure with an afterload reducer impact stroke volume?
Increases stroke volume
Reduces end systolic volume and energy requirements of the heart.
What is the impact of increased filling pressure in heart failure patients?
Helps the heart acutely but may cause dilation long-term
Increased volume retention drives up preload, aiding in filling.
True or False: Aortic stenosis is the most common valve problem.
True.
What is the relationship between heart rate and cardiac output in heart failure?
Higher heart rate is needed to maintain normal cardiac output
This compensates for reduced stroke volume.
