Common on ITU and is associated with increased mortality.
Impairs systolic function by:
- LV emptying occurs before aortic pressure has fully decreased reducing SV due to increased afterload.
- Less time for LV filling reducing preload.
- Less time for calcium to be to be taken up into the sarcoplasmic reticulum after it is released in systole, reducing contractility & SV.
Generally preserved until >100bpm when SV & CO reduces.
Diastolic function impacted due to the loss of atrial systole. Reduces LA emptying leading to reduced LVEDP and increased LAP – leads to LA dilatation.
Patients with diastolic impairment who rely on atrial contraction for LV filling tolerate AF particularly poorly.
Impact for Echo:
Variability in systolic function measures require more values to be taken and averaged.
Need to take 10 consecutive readings and average.
Very infrequently actually performed but need to average as many readings as possible.
This includes LVOT VTI for SV, FAC, FS, EF etc.
Theoretically can use two consecutive readings if the R-R intervals are the same but less practical.
For diastolic function – both high LVEDP and AF increase LA volume challenging to identify cause.
Take MV inflow readings over 5-10 cardiac cycles.
More important to take readings of good quality doppler traces than consecutive beats.
E velocity cannot be used to estimate LAP. Will reduce in early diastolic failure but then increases AF with rise in LAP. Can use trend on same patient but not useful in ITU.
Better to use E dec time if EF <45%:
- <150ms predicts PAWP >15mmHg.
- <120ms predicts PAWP >20mmHg (sensitivity 100%, specificity 96%).
Can use IVRT but is HR dependent and not ideal measure for clinical practice. <65ms predicts PAWP >15mmHg.
Propagation velocity – slope of aliasing velocity of LV inflow using colour M-mode in A4C.
E/Vp has good correlation with PAWP but not particularly practical to measure. E/Vp >1.4 = PAWP >15.
Best measure is for E/e’ (surprise). Less sensitive and specific than some measures but used in combination is very useful. E/e’ >11 suggests PAWP >15mmHg (sensitivity 75%, specificity 93%).