DETERMINATION OF LEFT-VENTRICULAR CHAMBER STIFFNESS FROM THE TIME FORDECELERATION OF EARLY LEFT-VENTRICULAR FILLING

Background A noninvasive measure of left ventricular (LV) chamber stif fness (K-LV) would be clinically useful. Our theoretical analysis pred icts that K-LV can be calculated from the time for deceleration of LV early filling (t(dec)) by K-LV=rho . L/A .(pi/2 . 1/t(dec))(2) where r ho=density of blood, L=effective mitral length, and A=mitral area. Met hods and Results We tested this hypothesis in eight conscious dogs ins trumented for measurement of LV pressure (P) with use of a micromanome ter 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 grad ed doses of phenylephrine. We assumed that rho=1.0 and that L/A=3.4. T hus, we predicted that K-LV=(0.08/t(dec))(2). The LV filling pattern w as determined from the derivative of LV volume (dV/dt). t(dec) was mea sured 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 t hat 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 e stimate 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.