Can left ventricular diastolic stiffness be measured noninvasively?

Background: 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. Methods: Twenty-five patients (age 54 ± 12 years) with ischemic heart disease (n = 19) or primary LV dysfunction (n = 6), with a wide range of DT (79-324 ms) and ejection fraction (8%-57%), underwent simultaneous assessment of LV pressure by micromanometer and volume by 2-dimensional (2D) echocardiogrpahy-guided Doppler mitral flow velocity (where volume = mitral flow velocity integral × annular area) calibrated to 2D echocardiography stroke volume. Invasive K_lv [delta pressure (from minimum to end-diastolic)/delta volume (during the same time interval)] was obtained at baseline and in 23 patients after LV unloading by prostaglandin E₁ (30-60 ng/kg/min) (n = 12), nitroglycerin (0.2 mg) (n = 9) or magnesium (1 g) (n = 2). Noninvasive K_lv was estimated according to the above formula. Results: In this set of patients with normal mitral annular area (3.9 ± 1.1 cm²/m²), multivariate analysis showed that DT is inversely related to K_lv (P < .001) but not to left atrial chamber stiffness, LV volume, relaxation time constant, mitral valve opening pressure, or area. The relation between noninvasively calculated and directly measured K_lv was close to the line of identity under all conditions, (y = 0.93x + 0.05, r = 0.67, n = 48, P < .001), although with a wide standard error of the estimate (0.26 mm Hg/mL). Conclusion: We conclude that K_lv can be calculated ± 0.5 mm Hg/mL from noninvasively measured DT in patients.