Ventricular diastolic impedance Z(t): validation of a new, model-based image processing derived index of global diastolic function

The quest for a noninvasive, global index of left ventricular (LV) diastolic function has not yet been attained. Current echocardiographic methods extract components of diastolic function from selected aspects of transmitral flow velocity, ventricular geometry and wall motion. Diastolic left ventricular pressure P(t) and transmitral flow Q(t) define global diastolic impedance as Z(t)=P(t)/Q(t). Since P(t) requires cardiac catherization, we expressed P(t) via the nonsteady Bernoulli equation using Doppler echocardiographically measurable transmitral flow velocity v(t) and acceleration v=dv/dt. For validation we compared catheterization (invasively) derived Z_inv(t) with echo (noninvasively) derived Z_noninv(t) and found excellent agreement. We conclude that the echocardiographically determined LV diastolic impedance Z_noninv(t) provides a physiologically sound quantitative index of global LV diastolic function