Exam 1: 28 Jan 25 CO and Valve Dysfunction Flashcards
What is cardiac output?
The volume of blood the heart pumps per minute
Normal cardiac output is around 5 liters per minute.
What is the role of nitric oxide donors like sodium nitroprusside and nitroglycerin?
They have mixed vasodilatory effects, reducing systemic filling pressure and resistance to venous return
They help improve blood flow back to the heart.
What is the function of ACE inhibitors?
They primarily act as arterial vasodilators, reducing afterload
They have various effects, including lowering blood pressure.
What happens to cardiac function with aortic stenosis?
It leads to high ventricular pressures and reduced stroke volume
Compensatory mechanisms may include increased preload and heart rate.
How is mitral regurgitation characterized?
It resembles an ‘M’ shape
Understanding the shape can help distinguish it from aortic regurgitation.
Define preload.
The volume of blood in the ventricles at the end of diastole
It affects stroke volume directly.
Define afterload.
The resistance the heart must overcome to eject blood
High afterload can reduce stroke volume.
What is contractility?
The ability of the heart muscle to contract
It is influenced by factors like calcium availability and heart rate.
What is the shape of aortic regurgitation on a pressure-volume loop?
It resembles an ‘A’ lying on its side
This shape helps in identifying the condition.
True or False: Pressure-volume loops are clinically measured.
False
They are crucial for understanding heart function but are not directly measured in clinical settings.
What do increased venous tone and sympathetic nervous system activation do during cardiac failure?
They compensate for decreased cardiac output
These mechanisms help maintain perfusion to vital organs.
Fill in the blank: _______ is the reduction of blood flow back to the heart.
Resistance to venous return
This can be influenced by medications like nitroglycerin.
What does mitral valve stenosis lead to?
Reduced stroke volume and increased preload
It affects the filling of the heart chambers.
What are the consequences of improper valve function?
Difficulty in ejecting blood and backward flow into heart chambers
It can lead to further heart damage over time.
What is hydralazine known for?
It is an arterial vasodilator with an unknown mechanism of action
It’s less commonly used in acute settings due to delayed onset.
What is the significance of understanding pressure-volume loops?
They help in understanding heart function and valve dysfunction
Important for exam preparation and clinical assessments.
What is the impact of high preload on heart function?
It may lead to heart failure over time
Excessive preload can cause stress on the heart muscle.
What happens during myocardial infarction (MI)?
Cardiac output decreases and right atrial pressure increases
Compensatory mechanisms may kick in to stabilize hemodynamics.
List the three key factors that influence normal cardiac output.
- Preload
- Afterload
- Contractility
These factors are crucial for maintaining efficient heart function.
What is the role of the sympathetic nervous system in cardiac function?
It maintains normal activity and compensates for decreased output
High sympathetic activity can stress the heart.
What should students focus on for upcoming tests regarding cardiac output and return curves?
Understanding images, bullet points, and key talking points discussed in class
Visual aids are essential for retention and comprehension.
What happens to cardiac output when the heart is damaged?
Cardiac output is too low, approximately half normal.
This occurs because the heart is no longer functioning effectively as a pump.
What is significantly elevated when the heart struggles to pump effectively?
Right atrial pressure.
This is expected when the heart is not pumping well, leading to pressure backup.
What role does the nervous system play when cardiac output is low?
It increases venous tone and tells the heart to beat stronger.
This is part of the body’s short-term compensation mechanisms.
What is the effect of catecholamines on the heart during an acute myocardial infarction?
They increase heart strength and rate to improve cardiac output.
Norepinephrine is released to stimulate the heart.
What causes right atrial pressure to remain elevated over time?
Fluid retention and high systemic filling pressure.
This is a result of the heart struggling to pump effectively.
What does preload refer to?
The pressure available to fill the heart with blood.
Preload is measured in millimeters of mercury.
What is afterload?
The pressure the heart must pump against, specifically outside the aortic valve.
Higher afterload makes it more difficult for the heart to pump blood.
How is contractility defined?
The change in stroke volume when preload and afterload are constant.
It is not directly correlated to preload or afterload.
Fill in the blank: The body compensates for heart problems by tightening _____ and reducing compliance.
veins.
True or False: High sympathetic activity is desirable for long-term heart function.
False.
Long-term high sympathetic activity can predispose individuals to arrhythmias.
What must cardiac output achieve to maintain life?
Approximately five liters per minute.
This is necessary for adequate oxygen and nutrient delivery.
What happens to catecholamine release as blood volume expands?
Catecholamine release is typically dialed back.
This helps in achieving a more stable cardiovascular function.
What physiological change occurs when a person stands up from a seated position?
The central nervous system tightens blood vessels to prevent fainting.
This is an important adjustment to maintain blood flow to the brain.
What is the relationship between venous return and systemic filling pressure?
Higher systemic filling pressure improves venous return to the heart.
This is crucial for maintaining cardiac output.
What is indicated by a right atrial pressure significantly higher than normal?
The heart is struggling to pump effectively.
This condition often results from fluid retention and impaired cardiac function.
What are the main effects of catecholamines in the circulatory system?
- Increase heart rate
- Increase contractility
- Tighten blood vessels.
These effects are part of the body’s short-term adaptation to cardiac stress.
What is contractility?
Contractility is defined as the change in stroke volume when preload and afterload are held constant.
It indicates the heart’s ability to squeeze harder, resulting in more blood ejected.
How is preload defined?
Preload is the pressure available to fill the heart, typically measured as end diastolic volume (EDV).
In this context, normal preload is associated with a filling volume of approximately 120 ml.
What happens to stroke volume when preload increases?
Increased preload generally results in increased stroke volume due to better filling of the heart.
This occurs because a higher preload allows for greater end diastolic volume.
What is afterload?
Afterload is the pressure the heart must pump against to eject blood, specifically the diastolic blood pressure in the aorta.
For this context, normal afterload is approximately 80 mmHg.
What is the relationship between afterload and stroke volume?
An increase in afterload may lead to a decrease in stroke volume because the heart needs to generate more pressure to open the aortic valve.
This results in a longer duration of contraction (Phase 2) and less time for ejection (Phase 3).
How does contractility affect stroke volume?
Increased contractility leads to a higher stroke volume when preload and afterload are held constant.
This is indicated by a steeper slope in pressure-volume loops.
What is end diastolic volume (EDV)?
End diastolic volume is the volume of blood in the ventricle at the end of filling, just before contraction begins.
In this context, EDV is typically around 120 ml.
What is end systolic volume (ESV)?
End systolic volume is the volume of blood remaining in the ventricle after contraction.
A higher ESV indicates that less blood was ejected during systole.
True or False: Afterload is defined as peak systolic pressure.
False.
Afterload is actually the diastolic blood pressure, not the peak systolic pressure.
What affects the duration of Phase 2 in the cardiac cycle?
Increased afterload requires the heart to build up pressure for a longer period, extending Phase 2.
This results in less available time for Phase 3, affecting stroke volume.
Fill in the blank: If preload is decreased, we can expect a _______ in stroke volume.
decrease
This is because reduced preload leads to less filling of the heart.
What is the significance of the top left corner of a pressure-volume loop?
It indicates the level of contractility, with steeper lines representing higher contractility.
The intersection of the lines shows how contractility changes under different conditions.
What happens to stroke volume if end diastolic volume remains normal but end systolic volume increases?
Stroke volume decreases.
This indicates that less blood was ejected from the heart during contraction.
What happens to the end systolic volume when stroke volume is lower but end diastolic volume is normal?
End systolic volume is higher than normal
This occurs because if the heart fills normally but ejects less, more blood is left over in the ventricle.
What is a common physiological response to a reduced stroke volume in terms of heart rate?
Elevated heart rate
This is often observed in individuals with high blood pressure.
True or False: A lower resting heart rate generally indicates a healthier heart.
True
While this is generally true, it is not always the case.
What effect does increased afterload have on the heart’s performance?
It makes the heart work harder
Increased afterload can lead to stress on the heart.
Fill in the blank: Reducing afterload typically ______ stroke volume.
increases
This occurs because the valve opens earlier and closes later, allowing more blood to be ejected.
What is the relationship between contractility and stroke volume?
Higher contractility leads to increased stroke volume
This is due to the heart walls squeezing harder, ejecting more blood.
What happens to end systolic volume when contractility is reduced?
End systolic volume increases
This occurs because less blood is ejected from the ventricle.
How does an increase in contractility affect blood pressure?
It typically increases blood pressure
Conversely, decreased contractility usually leads to lower blood pressure.
What is aortic valve stenosis?
A condition characterized by a high resistance valve
This condition makes it difficult for blood to be ejected from the heart.
What happens to ventricular pressures in aortic stenosis?
Ventricular pressures are high
This occurs because more pressure is needed to eject blood through the stenotic valve.
What compensatory mechanism does the body use when the heart struggles to maintain normal output?
Increased blood volume
This helps to enhance filling and improve cardiac output.
What is the effect of a stenotic aortic valve on pulse pressure?
Narrowed pulse pressure
This results from high ventricular pressures and lower pressures downstream.
True or False: An increase in preload is always beneficial for cardiac function.
False
While an increase in preload can help initially, it may lead to negative remodeling and worsening heart function over time.
How does the heart compensate for chronic reduced stroke volume due to aortic stenosis?
Increased heart rate
This compensatory mechanism is necessary to maintain normal cardiac output.
What happens to the time spent ejecting blood in the presence of a high resistance valve?
It is reduced
The high resistance makes it harder to build up the necessary pressure for ejection.
What is the expected outcome of treating a patient with aortic stenosis using afterload reducers?
Improved stroke volume and reduced energy requirements of the heart
This treatment facilitates easier ejection of blood from the heart.
What is aortic stenosis?
A condition where the aortic valve does not open fully, leading to narrowed pulse pressure and increased ventricular pressure.
In aortic stenosis, blood pressure on the other side of the valve is typically lower than proximal to the valve.
How does aortic stenosis affect pulse pressure?
Pulse pressure is narrowed, typically reduced from 40 to about 20.
This is a hallmark characteristic of severe aortic stenosis.
What happens to heart rate in response to aortic stenosis?
Heart rate is likely enhanced to maintain normal cardiac output.
The body compensates for reduced stroke volume by increasing heart rate.
What is the impact of a stenotic mitral valve on filling?
It leads to problems with filling, resulting in lower end diastolic volume and reduced stroke volume.
The resistance caused by the stenotic valve affects the flow from the left atrium to the left ventricle.
What compensatory mechanisms occur with a stenotic mitral valve?
Increased preload, systemic filling pressure, atrial pressure, and blood volume.
These adaptations aim to improve filling despite high resistance.
What are insufficient or regurgitant valves?
Valves that do not close tightly, allowing blood to leak backwards.
Both terms describe the same issue of ‘leaky’ valves.
How does a leaky aortic valve affect ventricular filling?
The ventricle fills from both the atrium and the aorta, increasing end diastolic volume.
This dual filling can initially help maintain stroke volume.
What happens to the ventricle over time with a leaky aortic valve?
The walls of the ventricle stretch, leading to worse valve function and greater insufficiency.
Chronic volume overload can impair cardiac structure and function.
What is the relationship between pressure gradients and backward blood flow in aortic regurgitation?
Higher pressure in the aorta relative to the ventricle drives retrograde blood flow when the aortic valve is closed.
This occurs primarily when the ventricular pressure is low.
What is the significance of phase four in a pressure volume loop for a healthy heart?
Phase four is typically isovolumetric, indicating no blood movement into or out of the ventricles.
In a healthy heart, both pressure and volume remain stable during this phase.
What changes occur in the pressure volume loop with a leaky aortic valve?
The loop shows increased ventricular volume during phase four, indicating backward blood flow.
This results in a curved line rather than a straight vertical line.
What happens during early diastole in the context of a leaky aortic valve?
The ventricle fills from both the atrium and retrograde flow from the aorta.
This dual filling can enhance stroke volume temporarily.
What is the potential consequence of prolonged compensation for mitral valve stenosis?
Eventually leads to pulmonary edema due to high pressures in the lungs.
Chronic high filling pressures can impair gas exchange.
True or False: Aortic stenosis results in increased stroke volume.
False
Aortic stenosis typically results in reduced stroke volume due to impaired outflow.
Fill in the blank: The main issue with a stenotic mitral valve is a reduction in __________.
stroke volume
What are the effects of increased filling pressure on the heart?
Increased preload and higher systemic filling pressures.
This is an adaptive response to maintain cardiac output despite filling difficulties.
What happens to ventricular volume when the mitral valve is completely closed?
Ventricular volume increases while blood comes from the aorta.
This indicates a potential leak or backflow occurring in the heart’s valves.
At what point does the aortic valve normally open?
The aortic valve normally opens at the end of phase one.
In cases of aortic regurgitation, it opens at a lower pressure than normal.
What is the relationship between aortic pressure and aortic valve opening during regurgitation?
Aortic pressure is probably low when the aortic valve opens during regurgitation.
How does aortic stenosis affect pulse pressure?
Aortic stenosis causes a narrowing of the pulse pressure.
What type of pulse pressure is associated with aortic insufficiency?
Aortic insufficiency is associated with a wide pulse pressure.
What occurs when the mitral valve is leaky?
Blood moves from the ventricle back into the atria.
When does backward blood flow occur with a leaky mitral valve?
Backward blood flow occurs when the ventricular pressure is higher than the atrial pressure.
What phase of contraction shows a curve indicating blood moving out of the ventricle when the aortic valve is still closed?
Phase two shows a curve indicating blood moving out of the ventricle.
What happens to the pressures in the ventricle and atria during phases two, three, and four?
Ventricular pressure is higher than atrial pressure during these phases.
What shape is typically associated with mitral regurgitation on pressure-volume loops?
The shape resembles an ‘M’.
What shape is typically associated with aortic regurgitation on pressure-volume loops?
The shape resembles an ‘A’ on its side.
What is indicated by the ISO volumetric portion in pressure-volume loops?
It indicates that the balance is no longer isovolumetric due to valve insufficiency.
How should clinicians assess the impact of bad valves on heart function?
They should monitor the valves before they start affecting the overall heart function.
What happens when heart valves do not open properly?
It creates a difficult time ejecting blood.
What is a key factor in the function of heart valves?
Valves must fit together properly to function correctly.
Fill in the blank: The portion of the pressure-volume loop where blood leaks backward during mitral regurgitation occurs primarily in phase _______.
two.
True or False: Aortic regurgitation leads to a decrease in stroke volume.
False.
