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.
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.
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
Measure speed of blood flow past the aortic valve during systole
Aortic VTI is proportional to cardiac output (CO)
