Mitral inflow parameters have been used most widely in the evaluation of left ventricular (LV) diastolic function. However, when the mitral E and A waves are completely fused, mitral inflow parameters cannot provide information about the LV diastolic function. LV filling pressure, mitral inflow, mitral annulus velocity, and tau (tau) were measured in 59 patients with sinus rhythm when mitral E and A waves were completely fused with right atrial pacing. When mitral E and A waves were completely fused, tau correlated with the peak fused mitral annulus velocity (r = -0.60, P <.001), and peak fused mitral annulus velocity of less than 12.5 cm/s best discriminated prolonged (>/=50 ms) from normal tau, with a sensitivity of 78% and specificity of 69%. The peak fused mitral inflow velocity to peak fused mitral annulus velocity ratio correlated with LV filling pressure (r = 0.62, P <.001). A ratio of at least 8, could predict elevated LV filling pressure (>/=15 mm Hg) with a sensitivity of 65% and specificity of 74%. In conclusion, even when mitral E and A waves are completely fused, mitral annulus velocity can be used in the evaluation of LV diastolic function.