Impact of varying diastolic pressure fitting technique for the reservoir-wave model on wave intensity analysis

Q: What are the key findings of this study?

Varying diastolic pressure decay fitting techniques left peak reservoir pressure (≤6% change), its integral (≤3%), and wave speed (≤8%) largely stable, while altering excess pressure integral up to 64%.

Q: What is the clinical evidence from this study?

Study design: Cross-Sectional. Population: Healthy humans free from manifest cardiovascular disease (n=1037). Intervention: Diastolic pressure decay fitting techniques for the reservoir-wave model (varying degrees of freedom [2 DOF vs 3 DOF] and diastolic fitting window length [whole diastole vs last two-thirds of diastole]) vs. Comparison across four fitting combinations (3 DOF whole, 2 DOF whole, 3 DOF 2/3, 2 DOF 2/3) and measured PU-loop vs excess PexUex-loop. Primary outcome: Sensitivity of reservoir pressure parameters (Prmax, PRI), excess pressure/velocity parameters (Pexmax, PEI, Uexmax), wave speed, and wave intensity parameters (FCW, BCW, FEW) to diastolic fitting technique (p=<0.05).

Q: What does this research mean for the field?

Peak reservoir pressure, its time integral, and wave speed are largely robust to different diastolic pressure decay fitting methods, whereas excess pressure and velocity parameters are highly sensitive to the fitting technique. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

Q: What question did this study set out to answer?

To examine how altering diastolic decay fitting techniques affects the derivation of reservoir and excess pressure, flow velocity components, and wave intensity parameters.

Nicola Pomella; Ernst Rietzschel; Patrick Segers; Ashraf W. Khir

doi:10.1177/0954411920959957

September 30, 2020Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in MedicineOpen Access

Impact of varying diastolic pressure fitting technique for the reservoir-wave model on wave intensity analysis

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Key result

Varying diastolic fitting alters excess pressure integral up to ~64% while reservoir parameters remain stable.

P<0.05
n=1,037

Figures

Why the study?

While the reservoir-wave concept remains debated, there is no consensus on the best fitting method for calculating the reservoir pressure waveform.

Does varying the diastolic pressure decay fitting technique (degrees of freedom and fitting window length) affect calculated reservoir-wave hemodynamic parameters, wave speed, and wave intensity parameters in healthy middle-aged adults?

Key Points

To examine how altering diastolic decay fitting techniques affects the derivation of reservoir and excess pressure, flow velocity components, and wave intensity parameters.
Analyzed common carotid artery pressure and flow velocity waveforms measured via applanation tonometry and Doppler ultrasound in N=1037 healthy adults aged 35 to 55 years from the Asklepios study.
Applied different fitting techniques (2 vs 3 degrees of freedom, and whole window vs last two-thirds of diastole) to the diastolic decay of measured arterial pressure to calculate the asymptotic pressure decay and reservoir pressure waveform.
Calculated wave speed using the PU-loop method and determined wave intensity analysis parameters derived from excess pressure and excess velocity.
Peak reservoir pressure decreased slightly from 3 to 2 degrees of freedom (-6% for whole window, -5% for two-thirds window) and its time integral remained stable (-3% to -1%), showing that peak reservoir pressure and reservoir pressure integral are largely robust to fitting methods.
Peak excess pressure increased significantly from 3 to 2 degrees of freedom (+32% for whole window, +16% for two-thirds window), and the excess pressure integral increased by +64% (whole window) and +36% (two-thirds window).
Wave speed was minimally affected across settings (changing +7% from 3 to 2 degrees of freedom in the whole window, and -1% in the two-thirds window), whereas forward compression wave area increased by +38% (whole window) and +14% (two-thirds window).

Study Design

Type

Cross-Sectional (n=1,037)

Multicenter

No

Structured PICO

Does varying the diastolic pressure decay fitting technique (degrees of freedom and fitting window length) affect calculated reservoir-wave hemodynamic parameters, wave speed, and wave intensity parameters in healthy middle-aged adults?

P

Population

1,037 healthy adults aged 35 to 55 years (51.2% female) free from manifest cardiovascular disease from the Belgian Asklepios population cohort.

E

Exposure

Diastolic pressure decay fitting techniques for the reservoir-wave model applied to common carotid applanation tonometry pressure and pulsed-wave Doppler ultrasound flow velocity waveforms, varying degrees of freedom (3 DOF [free-fitting Pn, P∞, and b] vs 2 DOF [fixing Pn to measured dicrotic notch pressure and free-fitting P∞ and b]) and diastolic window length (whole diastole vs last two-thirds [2/3] of diastole).

C

Comparator

Cross-comparison among the four fitting method combinations (3 DOF whole, 2 DOF whole, 3 DOF 23, 2 DOF 23) and between measured waveforms (PU-loop) and excess waveforms (PexUex-loop).

O

Outcome

Hemodynamic parameters (peak reservoir pressure [Prmax], reservoir pressure integral [PRI], peak excess pressure [Pexmax], excess pressure integral [PEI], peak reservoir and excess velocities [Urmax, Uexmax], asymptotic pressure [P∞], diastolic rate constant [b], systolic rate constant [a], mean square error [X2]) and wave intensity parameters (wave speed [c], forward compression wave area [FCW], backward compression wave area [BCW], and forward expansion wave area [FEW]).surrogate

Main Result

p-value: p=<0.05

Peak reservoir pressure, reservoir pressure time integral, and wave speed are robust against variations in diastolic pressure decay fitting methods, making them more reliable non-invasive vascular diagnostic indicators than excess pressure, velocity, and wave intensity parameters.

Limitations

The last third (1/3) of diastole fitting window used in some literature was not evaluated.
Reservoir and excess pressures were calculated using only the pressure waveform measured at the carotid artery rather than simultaneous pressure and velocity at the aortic root.
The clinical applicability of the reservoir-wave theory and its underlying assumptions remains a matter of debate.
Only a single exponential decay model was evaluated rather than a multi-exponential approach.
Pressure and flow velocity measurements were recorded sequentially rather than simultaneously and required post-processing alignment.
The last third (1/3) of diastole fitting window was not evaluated in this study.
Reservoir and excess pressures were calculated using only the carotid artery pressure waveform rather than aortic root pressure and velocity waveforms.
The underlying validity of the reservoir-wave theory and its clinical assumptions remains debated.
Only a single exponential diastolic decay model was used rather than a multi-exponential approach.
Carotid pressure and flow velocity measurements were recorded sequentially rather than simultaneously and required alignment.

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Implication

Reservoir pressure metrics remain stable across fitting methods; leaves open their preferential use as reliable non-invasive vascular indicators.

Abstract

The reservoir-wave model assumes that the measured arterial pressure is made of two components: reservoir and excess. The effect of the reservoir volume should be excluded to quantify the effects of forward and backward traveling waves on blood pressure. Whilst the validity of the reservoir-wave concept is still debated, there is no consensus on the best fitting method for the calculation of the reservoir pressure waveform. Therefore, the aim of this parametric study is to examine the effects of varying the fitting technique on the calculation of reservoir and excess components of pressure and velocity waveforms. Common carotid pressure and flow velocity were measured using applanation tonometry and doppler ultrasound, respectively, in 1037 healthy humans collected randomly from the Asklepios population, aged 35 to 55 years old. Different fitting techniques to the diastolic decay of the measured arterial pressure were used to determine the asymptotic pressure decay, which in turn was used to determine the reservoir pressure waveform. The corresponding wave speed was determined using the PU-loop method, and wave intensity parameters were calculated and compared. Different fitting methods resulted in significant changes in the shape of the reservoir pressure waveform; however, its peak and time integral remained constant in this study. Although peak and integral of excess pressure, velocity components and wave intensity changed significantly with changing the diastolic decay fitting method, wave speed was not substantially modified. We conclude that wave speed, peak reservoir pressure and its time integral are independent of the diastolic pressure decay fitting techniques examined in this study. Therefore, these parameters are considered more reliable diagnostic indicators than excess pressure and velocity which are more sensitive to fitting techniques.

Discussion

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Cite This Study

Pomella et al. (2020) conducted a cross-sectional in Healthy humans free from manifest cardiovascular disease (n=1,037). Diastolic pressure decay fitting techniques for the reservoir-wave model (varying degrees of freedom [2 DOF vs 3 DOF] and diastolic fitting window length [whole diastole vs last two-thirds of diastole]) vs. Comparison across four fitting combinations (3 DOF whole, 2 DOF whole, 3 DOF 2/3, 2 DOF 2/3) and measured PU-loop vs excess PexUex-loop was evaluated on Sensitivity of reservoir pressure parameters (Prmax, PRI), excess pressure/velocity parameters (Pexmax, PEI, Uexmax), wave speed, and wave intensity parameters (FCW, BCW, FEW) to diastolic fitting technique (p=<0.05). Varying diastolic pressure decay fitting techniques left peak reservoir pressure (≤6% change), its integral (≤3%), and wave speed (≤8%) largely stable, while altering excess pressure integral up to 64%.

synapsesocial.com/papers/6a7c656152b1b26805401238 https://doi.org/10.1177/0954411920959957

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Impact of varying diastolic pressure fitting technique for the reservoir-wave model on wave intensity analysis

Figures

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

Impact of varying diastolic pressure fitting technique for the reservoir-wave model on wave intensity analysis

Figures

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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