AUTOMATED-METHOD FOR CHARACTERIZATION OF DIASTOLIC TRANSMITRAL DOPPLER VELOCITY CONTOURS - EARLY RAPID FILLING

Doppler echocardiographic studies of transmitral flow have become a ro utine clinical tool for the assessment and characterization of ventric ular diastolic (filling) function. We have previously derived a parame trized diastolic filling (PDF) formalism for the purpose of diastolic function assessment using Doppler echocardiography. The model accommod ates the mechanical ''suction'' feature of early diastolic filling of the heart by using a simple harmonic oscillator (SHO) as a paradigm fo r the kinematics of filling. PDF model predictions of transmitral flow velocity have shown excellent agreement with human echocardiographic Doppler contours (temporal profiles) when a visual, transparency overl ay method of model fit to clinical Doppler contour comparison was used . The determination of PDF model parameters from the clinical Doppler contour is equivalent to the solution of the ''inverse problem'' of di astole. Previously, this determination consisted of a manual, iterativ e method of graphical overlay, in which model predicted contours were visually compared with the echocardiography machine generated Doppler contour using transparencies. To automate the process of model paramet er estimation (i.e., solution of the ''inverse problem'') for the earl y or ''rapid filling'' phase of diastole (known in cardiology as the E -wave of the clinical Doppler velocity profile [DVP]) we recorded the acoustic pulsed Doppler signal using the forward channel of a commerci al echocardiography machine. The Doppler spectrogram for a particular E-wave was recreated using short-time Fourier transform processing. Th e maximum velocity envelope (MVE) was extracted from the spectrogram. The PDF model was fit to the E-wave MVE using a Levenberg-Marquardt (i terative) algorithm by the requirement that the mean-square error betw een the clinical data (MVE) and the model be minimized. Because the mo del is linear, all of the PDF parameters for the Doppler E-wave can be uniquely determined. We show that: (1) solution of the ''inverse prob lem of diastole'' is possible; (2) clinical Doppler E-wave contours ca n be accurately reproduced and quantified using the PDF formalism and its parameters; and (3) our proposed, automated method of PDF paramete r determination for the E-wave is robust.