Diabetes and diastolic function: Stiffness and relaxation from transmitral flow

To characterize the mechanism by which diabetes affects the heart in diabetic (n = 15) and age-matched control subjects (n = 15), we quantified and compared diastolic function (DF) in terms of chamber stiffness and viscosity/relaxation by analyzing Doppler E- and E′-waves and simultaneous (high-fidelity) hemodynamic data. We compared τ, standard Doppler indexes and indexes of stiffness and viscosity/relaxation computed via the parameterized diastolic filling (PDF) formalism. Three PDF parameters uniquely characterize each E-wave in terms of load (xo), viscoelasticity or viscosity/relaxation (c) and stiffness (k). Significant differences for c (p = 0.00004), the peak atrioventricular pressure gradient (kxo) (p = 0.02) and the stored elastic energy available for early filling (1/2kxo2) (p = 0.04) were found. The only conventional index attaining significance was E-wave acceleration time (p = 0.007). Neither time constant of isovolumic relaxation (τ) nor E-wave deceleration time, E′, k or xo differentiated between groups. We conclude that PDF based DF assessment differentiates between diabetic and nondiabetic controls better than conventional echo- or cath-based indexes. Our results in humans agree with published results from animal studies. We conclude that diabetes affects the heart via a quantifiable increase in chamber viscoelasticity (c) rather than an increase in chamber stiffness (k) and that phenotypic characterization of diabetic cardiomyopathy is facilitated by DF assessment via the PDF formalism. (E-mail: sjk@wuphys.wustl.edu)