A noninvasive estimation of left ventricular (LV) diastolic chamber stiffness (K(LV)) is still a challenge. Experimental data suggests that K(lv) can be obtained by using Doppler mitral flow deceleration time (DT) as the only variable: K(lv) = (70/[DT-20])(2) mm Hg/mL. We assessed the accuracy of this noninvasive estimate of K(lv) by comparing it with invasive measurement of K(lv) in intact patients with a wide range of LV size and function under varying loading conditions.