Quantifying Diastolic Function: From E-Waves as Triangles to Physiologic Contours via the 'Geometric Method'.

Abstract

Conventional echocardiographic diastolic function (DF) assessment approximates transmitral flow velocity contours (Doppler E-waves) as triangles, with peak (Epeak), acceleration time (AT), and deceleration time (DT) as indexes. These metrics have limited value because they are unable to characterize the underlying physiology. The parametrized diastolic filling (PDF) formalism provides a physiologic, kinematic mechanism based characterization of DF by extracting chamber stiffness (k), relaxation (c), and load (x o ) from E-wave contours. We derive the mathematical relationship between the PDF parameters and Epeak, AT, DT and thereby introduce the geometric method (GM) that computes the PDF parameters using Epeak, AT, and DT as input. Numerical experiments validated GM by analysis of 208 E-waves from 31 datasets spanning the full range of clinical diastolic function. GM yielded indistinguishableaverage parameter values per subject vs. the gold-standard PDF method(k: R2=0.94, c:R2=0.95, x o :R2=0.95, p<0.01 all parameters). Additionally, inter-rater reliability for GM-determined parameters was excellent (k:ICC=0.956c:ICC=0.944, x o :ICC=0.993). Results indicate that E-wave symmetry (AT/DT) may comprise a new index of DF. By employing indexes (Epeak, AT, DT) that are already in standard clinical use the GM capitalizes on the power of the PDF method to quantify DF in terms of physiologic chamber properties.