Determination of Left Ventricular Chamber Stiffness From the Time for Deceleration of Early Left Ventricular Filling

Abstract

Background A noninvasive measure of left ventricular (LV) chamber stiffness (K LV ) would be clinically useful. Our theoretical analysis predicts that K LV can be calculated from the time for deceleration of LV early filling (t dec ) by \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[K_{LV}{=}\frac{{\rho}\ {\cdot}\ L}{A}\ {\cdot}\ (\frac{{\pi}}{2}\ {\cdot}\ \frac{1}{t_{dec}})^{2}\] \end{document} where ρ=density of blood, L=effective mitral length, and A=mitral area. Methods and Results We tested this hypothesis in eight conscious dogs instrumented for measurement of LV pressure (P) with use of a micromanometer and volume (V) with use of sonomicrometers. K LV was determined as the slope of the late diastolic portion of the LV P-V loop. K LV was varied from 0.99±0.35 to 2.58±0.92 mm Hg/mL with use of three graded doses of phenylephrine. We assumed that ρ=1.0 and that L/A=3.4. Thus, we predicted that K LV =(0.08/t dec ) 2 . The LV filling pattern was determined from the derivative of LV volume (dV/dt). t dec was measured from peak early filling to the end of early filling. Predicted K LV and actual K LV were closely correlated ( r =.94, SEE=0.06 mm Hg/mL, P <.05). The regression line was close to the line of identity (slope=0.95, intercept=0.13 mm Hg/mL). Dobutamine did not alter the relation between t dec and K LV . t dec determined from the mitral valve flow velocity measured with Doppler echocardiography correlated well with that measured by dV/dt ( r =.89, P <.01) but was 0.02 seconds longer. K LV -calculated t dec from the corrected Doppler t dec provided a good estimate of measured K LV ( r =.75, SEE=0.5 mm Hg/mL, P <.01). Conclusions LV chamber stiffness can be determined from the time for deceleration of LV early filling, which can be measured noninvasively.