title: E-wave deceleration time may not provide an accurate determination of LV chamber stiffness if LV relaxation/viscoelasticity is unknown.
abstract: Average left ventricular (LV) chamber stiffness (Delta P(avg)/Delta V(avg)) is an important diastolic function index. An E-wave-based determination of Delta P(avg)/Delta V(avg) (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 echocardiography-catheterization. To elucidate the mechanism by which LVs with indistinguishable DTs manifest distinguishable chamber stiffness, we use a validated, kinematic E-wave model (Kovács 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: DT(k) approximately pi/(2k). Using the kinematic model, we derive the general DT-chamber stiffness/viscoelasticity relation as follows: DT(k,c) = pi/(2skrt[k])+c/(2k)(where c and k are determined directly from the E-wave), which reduces to DT(k) when c << k. Validation involved analysis of 400 E-waves by determination of five-beat averaged k and c from 80 subjects undergoing simultaneous echocardiography-catheterization. Clinical E-wave DTs were compared with model-predicted DT(k) and DT(k,c). Clinical DT was better predicted by stiffness and relaxation/viscoelasticity (r(2) = 0.84, DT vs. DT(k,c)) jointly rather than by stiffness alone (r(2) = 0.60, DT vs. DT(k)). Thus LVs can have indistinguishable DTs but significantly different Delta P(avg)/Delta V(avg) 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.
authors.affiliation: Cardiovascular Biophysics Laboratory, Washington University, School of Medicine, St. Louis, MO, USA.
authors.forename: Leonid
authors.initials: L
authors.lastname: Shmuylovich
authors.forename: Sándor J
authors.initials: SJ
authors.lastname: Kovács
mesh_terms: D006328:Cardiac Catheterization; D003971:Diastole; D015150:Echocardiography, Doppler; D004548:Elasticity; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D008875:Middle Aged; D008955:Models, Cardiovascular; D009038:Motion; D009200:Myocardial Contraction; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012107:Research Design; D013997:Time Factors; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017725:Ventricular Pressure