Time Domain Resolution of Forward and Reflected Waves in the Aorta

Li, John K.‐J.

doi:10.1109/tbme.1986.325903

Cited by 82 publications

(47 citation statements)

References 8 publications

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“…6,7 Mean pressure and flow, are related through peripheral resistance, and because they are not waves they are subtracted from P m and Q m before the calculation. WIA is also based on measured pressure and flow (or velocity) where the changes in these signals are considered as wavelets used for analysis.…”

Section: Wsa and Wiamentioning

confidence: 99%

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Wave Separation, Wave Intensity, the Reservoir-Wave Concept, and the Instantaneous Wave-Free Ratio

2015

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Abstract-Wave separation analysis and wave intensity analysis (WIA) use (aortic) pressure and flow to separate them in their forward and backward (reflected) waves. While wave separation analysis uses measured pressure and flow, WIA uses their derivatives. Because differentiation emphasizes rapid changes, WIA suppresses slow (diastolic) fluctuations of the waves and renders diastole a seemingly wave-free period. However, integration of the WIA-obtained forward and backward waves is equal to the wave separation analysis-obtained waves. Both the methods thus give similar results including backward waves spanning systole and diastole. Nevertheless, this seemingly wave-free period in diastole formed the basis of both the reservoir-wave concept and the Instantaneous wave-Free Ratio of (iFR) pressure and flow. The reservoir-wave concept introduces a reservoir pressure, P res , (Frank Windkessel) as a wave-less phenomenon. Because this Windkessel model falls short in systole an excess pressure, P exc , is introduced, which is assumed to have wave properties. The reservoir-wave concept, however, is internally inconsistent. The presumed wave-less P res equals twice the backward pressure wave and travels, arriving later in the distal aorta. Hence, in contrast, P exc is minimally affected by wave reflections. Taken together, P res seems to behave as a wave, rather than P exc . The iFR is also not without flaws, as easily demonstrated when applied to the aorta. The ratio of diastolic aortic pressure and flow implies division by zero giving nonsensical results. In conclusion, presumptions based on WIA have led to misconceptions that violate physical principles, and reservoir-wave concept and iFR should be abandoned. (Hypertension. 2015;66:93-98.

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Section: Wsa and Wiamentioning

confidence: 99%

“…Both, however, give similar results. 6,7,13 It is important to note that the validity of estimation of Z c is not guaranteed throughout the complete arterial system. When measuring close to bifurcations (eg, in the common carotid or pulmonary artery), the reflection-free period can be too short.…”

Section: Wsa and Wia Are More Similar Than Generally Perceivedmentioning

confidence: 99%

Wave Separation, Wave Intensity, the Reservoir-Wave Concept, and the Instantaneous Wave-Free Ratio

2015

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“…This standard frequency‐domain method is equivalent to the time‐domain method 36, 37. FWA was calculated as the maximum minus the minimum of P f .…”

Section: Methodsmentioning

confidence: 99%

Misinterpretation of the Determinants of Elevated Forward Wave Amplitude Inflates the Role of the Proximal Aorta

Phan

Segers

et al. 2016

JAHA

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BackgroundThe hemodynamic basis for increased pulse pressure (PP) with aging remains controversial. The classic paradigm attributes a predominant role to increased pulse wave velocity (PWV) and premature wave reflections (WRs). A controversial new paradigm proposes increased forward pressure wave amplitude (FWA), attributed to proximal aortic characteristic impedance (Zc), as the predominant factor, with minor contributions from WRs. Based on theoretical considerations, we hypothesized that (rectified) WRs drive the increase in FWA, and that the forward pressure wave does not depend solely on the interaction between flow and Zc (QZc product).Methods and ResultsWe performed 3 substudies: (1) open‐chest anesthetized dog experiments (n=5); (2) asymmetric T‐tube model‐based study; and (3) human study in a diverse clinical population (n=193). Animal experiments demonstrated that FWA corresponds to peak QZc only when WRs are minimal. As WRs increased, FWA was systematically greater than QZc and peaked well after peak flow, analogous to late‐systolic peaking of pressure attributable to WRs. T‐tube modeling confirmed that increased/premature WRs resulted in increased FWA. Magnitude and timing of WRs explained 80.8% and 74.3% of the variability in the difference between FWA and peak QZc in dog and human substudies, respectively.ConclusionsOnly in cases of minimal reflections does FWA primarily reveal the interaction between peak aortic flow and proximal aortic diameter/stiffness. FWA is strongly dependent on rectified reflections. If interpreted out of context with the hemodynamic principles of its derivation, the FWA paradigm inappropriately amplifies the role of the proximal aorta in elevation of FWA and PP.

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“…and also 45 mg capoten (angiotensin converting enzyme inhibitor) tid p.o. We studied for several months on an almost daily basis arterial properties in a two year old healthy conscious dog (body mass of 30 kg), and calculated Zo [1,3] for each intervention using:…”

Section: Methodsmentioning

confidence: 99%

“…While mean P and mean Q provide an estimate of hemodynamic resistance, it is often desirable to consider the pulsatile nature of the waves. A fast time domain method for the resolution of aortic pressure and flow into their forward and reflected components has been described by Li [1]. This method is applied to data we collected from chronically instrumented dogs.…”

Section: Introductionmentioning

confidence: 99%

Wave reflection and characteristic impedance in the conscious dog as influenced by adrenergic intervention

Kerkhof

2001 Conference Proceedings of the 23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society

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2001-The combined measurement of aortic root pressure, flow and diameter permits determination of e.g. arterial compliance (C) and characteristic impedance (Zo). These systemic circulatory properties reflect the dynamic load to the left ventricle. Obviously, it is of clinical interest to study possible effects of cardiopharmacologic intervention on C and Zo. Therefore, the specific aims of this study are first to delineate the characteristics of the systemic circulation and second to analyze the influence of adrenergic agonists and blockers on C and Zo. We investigate these questions in the chronically instrumented dog by analyzing in particular effects of alpha-and beta-adrenergic drugs. We found that on average Zo amounts to 0.11 mmHg.s/ml, while medetomidine (by a rise of approximately 70%) causes the largest increase in Zo.

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Time Domain Resolution of Forward and Reflected Waves in the Aorta

Cited by 82 publications

References 8 publications

Wave Separation, Wave Intensity, the Reservoir-Wave Concept, and the Instantaneous Wave-Free Ratio

Wave Separation, Wave Intensity, the Reservoir-Wave Concept, and the Instantaneous Wave-Free Ratio

Misinterpretation of the Determinants of Elevated Forward Wave Amplitude Inflates the Role of the Proximal Aorta

Wave reflection and characteristic impedance in the conscious dog as influenced by adrenergic intervention

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