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

Cardiovascular Biophysics Laboratory, Washington University School of Medicine, St. Louis, Missouri

Submitted 29 September 2006 ; accepted in final form 8 January 2007

Average left ventricular (LV) chamber stiffness (P_avg/V_avg) is an important diastolic function index. An E-wave-based determination of P_avg/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: P_avg/V_avg = N(/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 P_avg/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 P_avg/V_avg has been validated, we reexpress the DT-stiffness (P_avg/V_avg) relation of Little et al. as follows: DT_k . Using the kinematic model, we derive the general DT-chamber stiffness/viscoelasticity relation as follows: DT_k,c = (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 (r² = 0.84, DT vs. DT_k,c) jointly rather than by stiffness alone (r² = 0.60, DT vs. DT_k). Thus LVs can have indistinguishable DTs but significantly different P_avg/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.

echocardiography; mathematical modeling; diastole