AV delays
E and A waves
The ideal AV delay allows for complete atrial kick (atria fully contracts and contributes fully to filling of ventricle) before the onset of ventricular systole.
This is the E and A waves on echo.
Isovolumetric contraction, relaxation and aortic flow also occurs in the cardiac cycle.
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E wave:
the passive filling of the ventricles (atrial diastole)
A wave:
physical contraction of the atria (atrial systole)
Isovolumetric Contraction:
volume of blood in ventricles is static – no more new blood enters ventricle
Aortic flow:
LV emptying into aorta
Isovolumetric Relaxation:
ventricles relax prior to any new inflow of blood.
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AV delays too long
the atrial contribution to diastolic filling terminates before ventricular depolarization, resulting in the waste of diastole and suboptimal preload for ventricular contraction
The E and the A waves fuse together
atrial contribution to the ventricular filling time is inappropriately reduced
AV delays too short
the end-diastolic filling flow (mitral A wave) will be suddenly interrupted due to the onset of a ventricular contraction and closure of the mitral valve
•Ventricular filling time may be cut short
•The atrial kick can be cut short
•Hemodynamics can be impaired
•This shows up by a snubbed or cut off A wave
Velocity time integral
VTI = velocity time integral
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Measure speed of blood flow past the aortic valve during systole
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Aortic VTI is proportional to cardiac output (CO)
