## Abstract

Average left ventricular (LV) chamber stiffness (ΔP _{avg}/ΔV_{avg}) is an important diastolic function index. An E-wave-based determination of ΔP_{avg}/ΔV_{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: ΔP_{avg}/ΔV_{avg} = N(π/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 ΔP_{avg}/ ΔV_{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 ΔP_{avg}/ΔV_{avg} has been validated, we reexpress the DT-stiffness (ΔP_{avg}/ΔV_{avg}) relation of Little et al. as follows: DT_{k} ≈ π/(2 √k). Using the kinematic model, we derive the general DT-chamber stiffness/viscoelasticity relation as follows: DT_{k,c} = π/(2 √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 ΔP_{avg}/ΔV_{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.

Original language | English |
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Pages (from-to) | H2712-H2720 |

Journal | American Journal of Physiology - Heart and Circulatory Physiology |

Volume | 292 |

Issue number | 6 |

DOIs | |

State | Published - Jun 2007 |

## Keywords

- Diastole
- Echocardiography
- Mathematical modeling