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

Conventional echocardiographic diastolic function (DF) assessment approximates transmitral flow velocity contours (Doppler E-waves) as triangles, with peak (E_peak), 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 E_peak, AT, DT and thereby introduce the geometric method (GM) that computes the PDF parameters using E_peak, 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 indistinguishable average 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 = 0.956 c: 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 (E_peak, 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.