HRR: Cardiodynamics III Flashcards
What is the Frank-Starling law?
Stroke volume of the ventricle increases in response to increased volume of blood filling the ventricle prior to contraction (preload)
This law illustrates the relationship between the volume of blood filling the heart and the strength of the subsequent contraction.
What is the best measure of preload?
Sarcomere stretch
Sarcomere stretch reflects the degree of stretch of cardiac muscle fibers, which correlates with preload.
What is preload?
The volume of the ventricle at the end of diastole just before contraction
Preload is crucial for determining the force of the heart’s contraction.
How does increasing preload impact the Frank-Starling curve?
Causes movement upward along the curve
An increase in preload enhances the stroke volume, shifting the curve upward.
How does decreasing preload impact the Frank-Starling curve?
Causes movement downward along the curve
A decrease in preload results in a reduced stroke volume, shifting the curve downward.
What are some factors that increase preload?
- Increased venous pressure
- Increased blood volume
- Increased venous return
These factors contribute to more blood filling the ventricles, thereby increasing preload.
What effect does squatting have on preload?
In short bursts, it will increase preload
Squatting can enhance venous return, thus increasing the volume of blood filling the heart.
How does reduced heart rate impact preload?
It will increase it
A slower heart rate allows more time for the ventricles to fill, thus increasing preload.
What is preload?
The volume of blood in the ventricles at the end of diastole
Preload is a key determinant of stroke volume and cardiac output.
How will reduced heart rate impact preload?
It will increase it
A slower heart rate allows more time for the ventricles to fill with blood.
How does valvular stenosis impact preload?
Increases it
Valvular stenosis restricts blood flow, leading to increased volume in the ventricles.
What is afterload?
The arterial pressure the ventricle needs to overcome to eject blood
Afterload is influenced by systemic vascular resistance and arterial compliance.
Describe how afterload impacts force-velocity curves.
Once the ventricle overcomes the pressure, velocity is fast; if not, force is high but velocity is flat
This illustrates the relationship between force exerted by the heart and the speed of blood ejection.
What is the relationship between force and velocity?
Low force = high velocity; High force = 0 velocity
This principle explains why a ventricle may exert a lot of force without generating velocity under high afterload.
How does heart rate impact afterload?
Increases it
A faster heart rate can lead to increased arterial pressure, thus increasing afterload.
How does reduced afterload impact the pressure-volume (PV) loop?
It will reduce preload, reduce pressure, decrease volume, and increase stroke volume (SV)
This occurs because the end-systolic volume (ESV) decreases from more blood being ejected, and ESV decreases at a faster rate than end-diastolic volume (EDV).
What is the impact of inotropy on a PV loop?
Stroke volume increases, slope of the end-systolic pressure-volume relationship (ESPVR) increases, and preload decreases due to more blood being ejected
This demonstrates the relationship between contractility and volume changes in the heart.
What happens to the PV loop in heart failure?
The loop is shifted right; both the EDV and ESV are increased due to poor pump action, and SV is reduced.
This reflects the heart’s inability to effectively pump blood.
