Parameters of the cardiac cycle; volume fractions; factors infuencing cardiac output Flashcards
What are the Volume fractions?
- EDV
- ESV
- SV
- CO
What are the parameters describing the heart cycle?
- compliance
- work and performance
What is the EDV?
End Diastolic Volume
- At the end of the diastole (maximal relaxation, right before the next heart contraction), the ventricles are maximally filled.
What is ESV?
End Systolic Volume
- When the ventricles re maximally emptied (end of systole, right before relaxation) there is still some blood remaining in them.
What is SV?
Stroke Volume
- Passes through the aorta at each cycle.
= EDV - ESV
What is CO?
Cardiac output
- The volume of blood pumped into the circulation by the heart in one minute.
CO = (EDV - ESV) x Frequency = SV x Frequency
How can you measure the cardiac output?
- Using Fick´s Principle
2. Using Stewart´s principle.
Why do you measure the Cardiac output?
It is a good measure of cardiac performance
Explain Fick´s principle:
Based on the law of conservation of mass.
- CO is based on the amount of oxygen that is taken up by the lung per unit time hsould equal the amount taken up by the tissues.
CO = total O2 uptake (1/min) / aterio-venous O2 difference (l/l).
Explain the Stewart´s principle:
From volume determination to Volume FLOW determination (V/time instead of V)
- Injecting Evans-blue IV, sample collection and analysis, plot curve, just before recirculation do extrapolation (intercept with X).
- Area under the extrapolated curve = CO.
What is Ventricular Compliance?
Dilating capacity (volume change taking place due to unit-pressure change, delta-V/delta-P
When is Ventricular Compliance important?
Important parameter of the adaptability of the heart. Closely related to the dialting ability of ventricles.
Connection between EDV, EDVP and SV in rest:
the pressure maintained by blood arriving from periphery (EDV ventricular pressure) is 5 Hgmm.
. that creates 60ml EDV.
Increase of EDVP in the connection between EDV, EDVP and SV.
- linearly increases EDV (+SV) until 25 Hgmm (from here Collagen prevents further dilation)
Ventricular compliance in old animals:
Decreased compliance
- The curve shifts to right
- the same EDVP cant dilate the heart to the same EDV
- at least two-fold EDVP is needed to achieve the same EDV.