TABLE 2.

Important limitations of tissue Doppler variables

Variable	Limitations
Doppler angulation error	The vector of the Doppler sample volume must deviate <20° from vector of myocardial motion to avoid significant underestimation of myocardial velocities
Which annulus: septal or lateral?	Given that early diastolic annular velocity (Ea) at the septal annulus is lower than Ea at the lateral annulus, the early diastolic velocity to Ea (E/Ea) ratio at the septal annulus is almost always higher than E/Ea at the lateral annulus. Ea at both annuli can be averaged to calculate E/Ea, especially in patients with regional wall motion abnormalities. Thus, E/Ea (septal) ≥15, E/Ea (lateral) ≥12 and E/Ea (average) ≥15 can be used to reflect elevated left ventricular filling pressures
Preserved ejection fraction (≥50%) versus normal hearts	In general, E/Ea is more accurate in estimating left ventricular filling pressures in patients with depressed, rather than preserved, ejection fraction
E/Ea ‘gray zone’	An E/Ea between 11 and 14 is a gray zone, in which case other variables are needed to accurately estimate left ventricular filling pressure: left atrial volume indexed to body surface area (a normal volume, <32 mL/m2, effectively rules out significant left atrial pressure elevation), pulmonary venous flow profile (systolic wave > diastolic wave, implying normal left ventricular filling pressures) and B-type natriuretic peptide (a level <50 pg/mL effectively excluding elevated left ventricular filling pressure)
Clinical situations in which E/Ea has not been well validated	The E/Ea is not generally used in patients with severe mitral annular calcification, mitral stenosis and mitral prosthetic valves. In patients with hemodynamically significant mitral regurgitation and in patients with atrial fibrillation, caution must be used when using E/Ea (see text). The E/Ea has not been validated in paced rhythm