L38 Hemodynamics Flashcards
What are the 4 important things upon which hemodynamic homeostasis depends?
- Preload
- Afterload
- Contractility
- Heart Rate
What does cardiac output depend upon?
CO = SV * HR
___ determines oxygen delivery; ___ determines organ perfusion.
Cardiac output; blood pressure
What is CO?
Measure of the volume of blood (and thus how much oxygen) can be delivered
What is SV?
How much blood the heart pumps per contraction
What three factors determine SV?
Preload, afterload, contractility
What is preload?
How much fluid is in the pump
What is afterload?
How much resistance there is to pumping
What is contractility?
How strong the pump is
Describe the axes of the Frank Starling curve.
X-axis: preload
Y-axis: SV
Describe the 4 points of the pressure volume loop, starting with A = bottom right corner.
A: MV closes
B: AV opens
C: AV closes
D: MV opens
When does the mitral valve shut?
When the pressure in the left ventricle is greater than the pressure in the left atrium
When does the atrial valve open?
When the pressure in the ventricle is greater than the pressure in the artery
Diastole (relaxation, filling) occurs from point ___ to ___.
D; A
Systole (contraction, emptying) occurs from point ___ to ___.
B; C
What is lucitropy?
The heart’s ability to relax and accept volume
How does the pressure volume loop shift to the left or right?
Increasing or decreasing the preload or left ventricular end diastolic pressure;
Adding volume shifts to the right
Diuresis, nitrates, and blood loss shifts to the left
The Frank Starling curve indicates that increased preload leads to increased ___ and therefore increased LV contraction and increased ___.
Sarcomere length; stroke volume
Compliance = ?
Change in volume/change in pressure
When does the atrial valve close?
When left ventricular pressure is exceeded by aortic pressure
How does the pressure volume loop shift up and down?
Increasing and decreasing afterload (arteriolar contraction)
How is afterload measured?
Wall tension
Increasing afterload ___ stroke volume.
Decreases (and vice versa)
The slope of the line at the top right of the pressure volume loop represents ___.
Contractility
