Frequency-Based Analysis of Diastolic Function: The Early Rapid Filling Phase Generates Negative Intraventricular Wave Reflections

Abstract

To assess global diastolic function (DF), both invasive and noninvasive methods have been utilized. Except for the end-diastolic pressure-volume relationship, currently all proposed parameters for diastolic function are derived purely from pressure or flow. To characterize the physiology of diastole in the context of atrioventricular pressure gradient generated transmitral flow, and in analogy to frequency-based characterization of ventricular-vascular coupling, we subjected the simultaneously recorded transmitral flow (E-wave) and micromanometric intraventricular pressure (LVP) waveforms to Fourier analysis in 20 subjects. This permitted computation of input impedance, characteristic impedance, the phase angle φ relating pressure to flow, and the complex reflection coefficient R * during the E-wave. We found that the magnitudes of input impedance were 32 ± 12, 13.9 ± 4.4, 37 ± 13, and 53 ± 23 mmHg s/m for DC, 1st, 2nd, and 3rd harmonics, respectively. The characteristic impedance was 30 ± 15 mmHg s/m. The magnitude and phase angle of complex reflection coefficient R * were 0.43 ± 0.11 and 3.58 ± 0.52 rad, respectively. The magnitude of the input impedance carrying most oscillatory power (1st harmonic) is lower than the characteristic impedance, verifying our finding that the real portion of R * was negative. We also found that E waves with prolonged deceleration time (DT > 180 ms-"delayed relaxation" pattern) manifest increased phase differences between pressure and flow, voiding an optimal pressure-flow relationship. These findings elucidate the frequency-based (amplitude/phase) mechanisms by which early diastolic mechanical ventricular suction (dP/dV< 0) achieves left ventricular filling.

Relationship of pulmonary vein flow to left ventricular short-axis epicardial displacement in diastole: model-based prediction with in vivo validation

“…The methodology employed has been previously described (2,21,26). Briefly, immediately before cardiac catheterization, a full two-dimensional Doppler examination is performed by an experienced sonographer using a standard clinical imaging system (Acuson, Mountain View, CA) with a 3-MHz transducer in the catheterization laboratory.…”

Frequency-based analysis of the early rapid filling pressure-flow relation elucidates diastolic efficiency mechanisms

“…Despite the successful application of Fourier methods in characterizing arterial stiffness, little effort has been made to use similar methods to study the stiffness-related mechanisms of DF or DD. To overcome this limitation, we previously introduced the concept of impedance analysis as a method for DF characterization (28). In precise analogy to frequency-based analysis of pressure and flow applied to the peripheral circulation, our method determined input impedance, characteristic impedance, and the reflection coefficient of the left ventricle (LV) by analysis of pressure and flow during early rapid filling (Doppler E wave).…”

“…As anticipated from theoretical and physiological arguments based on the role of the LV as a suction pump, we found that the LV generates a negative reflection coefficient during the E wave due to the phase difference between pressure and flow. Moreover, filling in normal hearts operates very near the optimal phase angle (180°) that minimizes the reflection coefficient (28). The existence of an optimal phase angle (between P and Q) implies optimization between the dominant (1st harmonic) pressure wave and flow wave during early rapid filling.…”

Diastolic ventricular-vascular stiffness and relaxation relation: elucidation of coupling via pressure phase plane-derived indexes

“…The PDF formalism predicts transmitral flow velocity during early rapid filling (E wave). The viscoelastic damping/relaxation parameter c computed from the Doppler E wave has been shown to play a role in chamber stiffness (32,34), causing a phase shift between pressure and flow (58). It also manifests in characterizing the cardiovascular effects of diabetes (10,49), hypertension (31), caloric restriction (39), exercise, and heart failure (38,48).…”

“…Furthermore, because P and V can have different phases as a result of viscoelastic effects, stiffness, defined either as dP/dV or E(t) ϭ P(t)/[V(t) Ϫ V o ], relies on the assumption of minimal viscosity (or nearly steady state) change in P and V. However, previous work on viscous and elastic properties of the myocardium (55,56) shows that viscoelastic effects, are in general, not negligible. In diastole, for example, viscoelastic effects during relaxation cause a phase shift between pressure and flow (volume) (58). Therefore, using an alternative expression for lumped stiffness (such as Eq.…”