As ventricle relaxes blood from aortic flow back into ventricle so no true isovolumetric relaxation,so ventricle gets filled before mitral valve opens,throughout diastole ventricle gets filled from aorta so end diastolic volume is increased as shown in PV loop
By chronic dilatation of ventricle EDV increases
No true isovolumetric contraction as blood is coming from aorta;once the LVP > aortic diastoilic pressure’ventricle begins to eject the blood
↑EDV→↑ force of contraction (F-S law)
↑ ventricular peak pressure
↑ stroke volume ( width of PV loop)
ESV may not be ↑ amount due to ↑ in afterload,but if ventricle goes in failure ↑ in ESV → fall in peak systolic pressure & stroke volume.
Lt ventricular emptying impaired because of AS
High outflow resistance
Large pressure gradient
Peak systolic pressure in ventricle ↑↑
↑ wall stress,ventricle afterload
↓ stroke volume + ↑ end systolic volume
Width of PV loop ↓ because velocity of fiber shortens
Decreases by ↑ in afterload
↑ESV + venous return→↑EDV
↑EDV(preload)→↑ force of contraction-Frank Starling’s law
In severe AS-ESV↑ > EDV
Compensatory ↑EDV-by ventricular hypertrophy
↓EDV by increase stiffness of ventricle prevent normal filling
P-V LOOP In Mitral Stenosis
Decrease in EDV-As impaired LV filling[preload]
Decrease in stroke volume.
Decrease in cardiac output
Decrease in preload & decrease in aortic pressure.
Decrease ventricular wall stress[afterload]
Small decrease in end systolic volume.
PV LOOP IN Mitral Regurgitation
☛ In mitral regurgitation –LV ejects blood in aorta and Lt.Atrium ,so LA volume volume and LApressure increases so no isovolumetric contraction phase becoz blood begins to flow across mitral valve and back in to LA before aortic valve opens as soon as ventricular pressure exceeds LA pressure.
☛ Total output resistance on ventricle redused becoz of MR ,so endsystolic volume can be smaller than normal.
☛ There is no true isovolumetric relaxation becoz when aortic valve closes and ventricles begins to relax ,Mitral valve is not completely closed so blood continues to flow back in LA as long as LVP > LAP.
LVEDV and LVEDP both increases.
☛ Increase in EDV – Increase in wall stress→ increase afterload,if it were not then net effect is width of PV LOOP is increased.and ejection in aortais decreased.