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Departments of 1Physics, 2Biomedical Engineering, and 3Internal Medicine, Cardiovascular Biophysics Laboratory, Cardiovascular Division, Washington University School of Medicine, St. Louis, Missouri
Submitted 24 May 2005 ; accepted in final form 7 October 2005
Transmitral Doppler echocardiography is the preferred method of noninvasive diastolic function assessment. Correlations between catheterization-based measures of isovolumic relaxation (IVR) and transmitral, early rapid filling (Doppler E-wave)-derived parameters have been observed, but no model-based, causal explanation has been offered. IVR has also been characterized in terms of its duration as IVR time (IVRT) and by
, the time-constant of IVR, by approximating the terminal left ventricular IVR pressure contour as P(t) = P
+ Poet/
, where P(t) is the continuity of pressure, P
and Po are constants, t is time, and
is the time constant of IVR. To characterize the relation between IVR and early rapid filling more fully, simultaneous (micromanometric) left ventricular pressure and transmitral Doppler E-wave data from 25 subjects undergoing elective cardiac catheterization and having normal physiology were analyzed. The time constant
was determined from the dP/dt vs. P (phase) plane and, simultaneous Doppler E-waves provided global indexes of chamber viscosity/relaxation (c), chamber stiffness (k), and load (xo). We hypothesize that temporal continuity of pressure decay at mitral valve opening and physiological constraints permit the algebraic derivation of linear relations relating 1/
to both peak atrioventricular pressure gradient (kxo) and E-wave-derived viscosity/relaxation (c) but does not support a similar, causal (linear) relation between deceleration time and
or IVRT. Both predicted linear relations were observed: kxo to 1/
(r = 0.71) and viscosity/relaxation to 1/
(r = 0.71). Similarly, as anticipated, only a weak linear correlation between deceleration time and IVRT or
was observed (r = 0.41). The observed in vivo relationship provides insight into the isovolumic mechanism of relaxation and the changing-volume mechanism of early rapid filling via a link of the respective relaxation properties.
isovolumic relaxation; deceleration time; diastole; kinematic modeling
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