IVRT/T E-e´ ratio
Time intervals are less prone to hemodynamic alterations and hold
relevance in the load-altered MS milieu. Early clinical and auscultatory
study suggest that IVRT, the time interval between aortic valve closure
and mitral valve opening, is altered in MS.46 47 More
recent echocardiographic data suggests that IVRT demonstrates
significant relationship with invasive filling pressures in the setting
of mitral stenosis41 and in degenerative mitral
annular calcification.48 Further, shorter IVRT and
higher mitral A-wave velocity suggest elevated early diastolic LA
pressures. However, IVRT is not routinely measured in clinical practice
and is affected by heart rate and arterial pressure.40The time interval between E and e’
(TE-e’) has
demonstrated good relation to τ in animal and human studies and is
relatively load-independent.49 50 Using pulse wave
doppler, the E wave is recorded and the time interval between the onset
of QRS complex and the E wave is taken note of. Similarly, using TDI,
the time interval between the onset of QRS wave on the ECG and the e’
wave is noted. The difference between the two is depicted as the
TE-e’ time interval. IVRT is then divided by this value.
The normal value is <2. In normal LV diastolic function, E and
e’ occur at the same time or e’ may precede it. With elevated LA
pressure, the mitral E wave occurs earlier and annular e’ velocity is
delayed, lengthening TE-e’. In keeping with these
findings, Diwan et al. demonstrated that time-adjusted IVRT (IVRT/
TE-e’) displayed the strongest correlation with
capillary wedge pressure in MS and could track changes in capillary
wedge pressure after valve surgery.41 A value of
< 4.2 indicates increased LV diastolic pressures in MS with
reasonable accuracy. However, in the presence of atrial fibrillation,
these values may be hard to ascertain.