A&P CV2 Loops Flashcards
Ventricular pressure -volume loops demonstrate the changes in
Intraventricular volume and pressure during normal cardiac cycle
How many steps are in the ventricular loop cycle?
4
Isovolumetric Contraction Step 1 (B-> C) Happens just after
the QRS
Isovolumetric Contraction is the period between _____ and _____.
Mitral valve closing and aortic valve opening
Mitral valve closing and aortic valve opening occurs in what phase of loop cycle?
Isovolumetric contraction
What period has the highest O2 consumption?
Isovolumetric contraction
Isovolumetric contraction CYCLE begins
during diastole (at point B)
The left ventricle is filed with blood from teh left atrium (vol = 140ml) during what cycle?
Isovolumetric contraction
During Isovolumetric contraction, what does the ventricular pressure do? why?
Pressure increases b/c the valves are closed and the ventricle is filling.
Isovolumetric contraction follows what law?
Laplace’s Law
Laplace’s Law is (equation)
T=Pr
T=Pr
Laplace’s law
What part of the loop cycle follows Laplace’s Law?
Isovolumetric Contraction (B to C)
What is the ventricular end -diastolic volume?
~ 140ml
Cycle 2 of the ventricular P-Vol Loop is
Ventricular Ejection (C to D) or “emptying”
Ventricular Ejection is what cycle of the P-Vol loop?
cycle 2 (C to D)
Cycle 2, Ventricular Ejection is the period between what opening and closing?
aortic valve opening and closing
at what point (A, B, C, D) does the aortic valve open?
C
The aortic valve opens when pressure in …
the left Ventricle exceeds pressure in the aorta.
When the left Ventricle exceeds pressure in the aorta what happens? Where do we see this on the loop graph?
The aortic valve opens
See at point C
During Cycle 2, Ventricular Ejection blood is ejected into the aorta, and Ventricular Vol does what?
decreases
The volume ejected during cycle 2 from the ventricle is known as the:
Stroke Volume
Stroke volume can be measured on the P-Vol loop graph where?
The WIDTH of the loop
The volume remaining in the left ventricle (at Point A) is:
end-systolic volume
Equation for loop calculation of SV
SV = EDV - ESV
SV = EDV (point B) - ESV (point A)
Equation for loop calculation of EF
EF = SV / EDV
[(point B - point A)/ point B]
Cycle 3 of Ventricular P-Vol Loop is called
Isovolumetric relaxation
Isovolumetric relaxation occurs at what cycle in the loop?
cycle 3 - point D to point A
Isovolumetric relaxation is the period between
aortic valve closing and mitral valve opening.
the period between aortic valve closing and mitral valve opening is known as:
Isovolumetric relaxation (D to A)
What happens at point D?
the ventricle relaxes
Where does the Ventricle relax on the loop? (what point)
D
When the ventricle relaxes, what is happening?
The Ventricular pressure decreases to less than aortic pressure.
-Aortic valve closes.
Why is cycle 3 Isovolumetric? What’s happening?
The aortic valve closes.
B/c all the valves close again, ventricular vol. is constant (isovolumetric)
Ventricular Filling is what cycle of the P-Vol loop?
cycle 4. (A to B)
Cycle 4 is called what?
Ventricular Filling (point A to B)
Ventricular Filling (cycle 4) is the period just after what:
mitral valve opening (point A)
What point does the Mitral valve open?
Point A
At point D the ventricle
relaxes
Once left ventricular pressure decreases to less than the left atrial pressure, what happens?
the Mitral (AV) valve opens and filling of the ventricle begins.
During Ventricular Filling (cycle 4), ventricular volume increases to about:
140 ml (end-diastolic vol)
What is occurring at Point B ?
end diastolic volume
ventricular volume increasing
20% of ventricular filling is a result of the
atrial kick
Atrial Kick occurs when?
at the end of cycle 4; just before point B
Increased Preload refers to an
increase in ventricular End diastolic VOLUME (filling)
-result of increased venous return
Frank-Startling relationship:
Increased preload =
increased stroke volume
Increased SV is reflected on the P-Vol loop by
increased WIDTH
Preload (ventricular) increases from:
- exercise
- increased blood vol (pregnancy, over transfusion)
- excitement (sympathetic)
Preload (ventricular) decreases from:
- venodilators (ntg)
- diuretics (furosemide)
**Preload = **
Pumps up the heart
“Pumps up the Heart”
Preload
Increased afterload refers to
an increase in aortic PRESSURE
an increase in aortic PRESSURE refers to
increased afterload
afterload is aka
diastolic arterial pressure
diastolic arterial pressure is aka
afterload
Afterload is proportional to
TPR (total peripheral resistance)
Factors that increase afterload
HTN
Aortic Stenosis
If the ventricle must eject blood against a higher pressure, what will decrease?
stroke volume
Stroke volume is reflected on the P-Vol loop as the
width
How would decreased SV change the P-Vol loop?
Decrease the width
Decreased SV results in an increased
end systolic volume
End systolic volume is the volume
left behind after systole
We use what to decrease afterload?
vasodilators (hydralazine)
Increased contractility develops when the ventricle has a greater tension than usual during systole.
Causing an increase in: (two things)
SV and EF
Increased SV causes a decrease in
end systolic volume (ESV)
Contractility (and SV) increase with:
- catecholamines
- increased intracellular Ca++
- Digitalis (Increased Intracellular Na+ resulting in Increased intracellular Ca++)
Contractility (and SV) decrease with:
- Beta 1 blockade
- HF
- acidosis
- hypoxia/ hypercapnia
- catecholamines
- increased intracellular Ca++
- Digitalis
All do what to Contractility/SV?
Increase it
- Beta 1 blockade
- HF
- acidosis
- hypoxia/ hypercapnia
All do what to Contractility/SV?
Decrease it
Visual Explain what changes in the ventricular P-vol loop graphically with increases in:
(A) Preload
(B) Afterload
(C) Contractility
A- preload; vol increases. loop expands to the right.
B- afterload; Pressure increases. loop increases in height; left side of loop vol decreases.
C- contractility; Vol increases to the left and a slight increase in pressure height
SV is affected by (3 points)
- contractility
- afterload
- preload
SV CAP
Increased SV when Increased ___
Preload or Contractility
Increased SV when decreased ____
afterload
Decreased afterload does what to SV?
increases SV
Increased Contractility does what to SV?
Increases SV
Increased Preload does what to SV?
Increases SV
constancy of CO up to a pressure level of
160 mmHg
If pressure > 160mmHg; what happens to CO?
drops rapidly
Nerves that stimulate Heart
Vagus
Sympathetic nerves
Parasympathetic stimulation has a positive or negative effect on CO (curve)?
Negative
lowers the curve - lowering the RA pressure
Sympathetic stimulation has a positive or negative effect on CO (curve)
Generally positive
-graphed curve: zero, Normal, and a GREAT Improvement/Increase of CO with Maximum sympathetic stimulation
