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.