E-wave deceleration time may not provide an accurate determination of LV chamber stiffness if LV relaxation/viscoelasticity is unknown

Average left ventricular (LV) chamber stiffness is an important diastolic function index. Ail E-wave-based determination of (Little WC, Ohno M, Kitzman DW, Thomas JD, Cheng CP. Circulation 92: 1933-1939, 1995) predicted that deceleration time (DT) determines. stiffness as follows: Delta P-avg/Delta V-avg = N(pi/DT)(2) (where N is constant), which implies that if the DTs of two LVs are indistinguishable, their stiffness is indistinguishable as well. We observed that LVs with indistinguishable DTs may have markedly different Delta P-avg/Delta V-avg values determined by simultaneous echochardioaphy-catheterization. To elucidate the mechanism by which LVs with indistinguishable DTs manifest distinguishable chamber stiffness, we use a validated. kinematic E-wave model (Kovacs SJ, Barzilai B, Perez JE. Am J Physiol Heart Circ Physiol 252: H178-H187, 1987) with stiffness (k) and relaxation/viscoelasticity (c) parameters. Because the predicted linear relation between k and Delta P-avg/Delta V-avg has been validated, we reexpress the DT-stiffness (Delta P-avg/Delta V-avg) relation of Little et al. as follows: DTk approximate to pi/(2 root k). Using the kinematic model, we derive the general DT-chamber stiffness/viscoelasticity relation as follows: DTk(k,c) = pi/(2 root k) + c/(2k) (where c and k are determined directly from the E-wave), which reduces to DTk when c << k. Validation involved analysis of 400 E-waves by determination of five-beat averaged k and c from 80 subjects undergoing simultaneous echocardioaraphy-catheterization. Clinical E-wave DTs were compared with model-predicted DTk and DTk,c. Clinical DT was better predicted by stiffness and relaxation/viscoelasticity (r(2) = 0.84, DT vs. DTk,c) jointly rather than by stiffness alone (r(2) = 0.60 DT vs. DTk). Thus LVs can have indistinguishable DTs but significantly different Delta Pavg/Delta Vavg if chamber relaxation/viscoelasticity differs. We conclude that DT is a function of both chamber stiffness and chamber relaxation viscoelasticity. Quantitative diastolic function assessment warrants consideration of simultaneous stiffness and relaxation/viscoelastic effects.