Determination of early diastolic LV vortex formation time (T*) via the PDF formalism: A kinematic model of filling

The filling (diastolic) function of the human left ventricle is most commonly assessed by echocardiography, a non-invasive imaging modality. To quantify diastolic function (DF) empiric indices are obtained from the features (height, duration, area) of transmitral flow velocity contour, obtained by echocardiography. The parameterized diastolic filling (PDF) formalism is a kinematic model developed by Kovács et al which incorporates the suction pump attribute of the left ventricle and facilitates DF quantitation by analysis of echocardiographic transmitral flow velocity contours in terms of stiffness (k), relaxation (c) and load (xo). A complementary approach developed by Gharib et al, uses fluid mechanics and characterizes DF in terms of vortex formation time (T*) derived from streamline features formed by the jet of blood aspirated into the ventricle. Both of these methods characterize DF using a causality-based approach. In this paper, we derive T*'s kinematic analogue T*_kinematic in terms of k, c and xo. A comparison between T*_kinematic and T*_{fluid mechanic} obtained from averaged transmitral velocity and mitral annulus diameter, is presented. We found that T* calculated by the two methods were comparable and T*_kinematic correlated with the peak LV recoil driving force kx_o.