Artery Research

Volume 20, Issue C, December 2017, Pages 78 - 79

P122 CALCULATING RESERVOIR PRESSURE WITH OR WITHOUT FLOW INFORMATION: SIMILARITY AND ALGORITHMIC SENSITIVITY AT RADIAL ARTERY

Authors
Michael Ebner1, Kim Parker2, Tom Vercauteren3, 1, Sébastien Ourselin3, 1, Siegfried Wassertheurer4, Alun Hughes5, Bernhard Hametner4
1Translational Imaging Group, Centre for Medical Image Computing, Department of Medical Physics and Biomedical Engineering, University College London, London, UK
2Department of Bioengineering, Imperial College London, London, UK
3Wellcome / EPSRC Centre for Interventional and Surgical Sciences, University College London, London, UK
4Center for Health & Bioresources, AIT Austrian Institute of Technology, Vienna, Austria
5Institute of Cardiovascular Science, University College London, London, UK
Available Online 6 December 2017.
DOI
10.1016/j.artres.2017.10.104How to use a DOI?
Abstract

Background: Reservoir pressure is typically estimated from the pressure waveform information only. Comparability with estimates made using pressure and flow depend on assumptions, e.g. a proportional relationship between excess pressure and flow [1]. In this study, we compared (i) results using flow and pressure versus pressure-only at the radial artery, and (ii) two different algorithms used in the literature for pressure- only analysis.

Methods: Reservoir pressure separations were performed on 95 hypertensive individuals where radial pressure and flow velocity waveform measurements were available [2]. Algorithm (F) used flow and pressure information [3]. Algorithms (P1) and (P2) refer to the two different pressure-only implementations as used in [4, 5], and [1, 6], respectively. Reservoir curves characterized by physiologically implausible parameters, i.e. a rate constant b < 0 or an asymptotic pressure P < 0, were discarded, leaving 63 subjects with valid reservoir pressure data.

Results: Estimated reservoir parameters are shown in Table 1. Algorithm (F) showed statistically significant differences in most of the parameters compared to (P1) and (P2), although, except time constant τ and asymptotic pressure P, there was a strong correlation between methods. Significant differences were observed in reservoir pulse pressure and area estimates between (P1) and (P2) despite their, in general, high correlation.

Radial artery pres (F) pres (P1) pres (P2) r(F,P1) r(F,P2) r(P1,P2)
PP [mmHg] 41.5±10.0 36.3±7.2 35.7±7.0 0.82* 0.82* 0.96*
Ap [mmHg s] 17.5±4.3 15.6±3.7 15.5±3.7 0.94* 0.94* 1.00*
τ [S] 0.3±0.1 0.6±0.4 0.6±0.3 0.36* 0.42* 0.88
P [mmHg] 65.7±10.3 63.9±15.2 64.8±12.6 0.45 0.53 0.79
a [1/s] 8.1±5.2 7.4±2.7 0.93
b [1/s] 2.2±1.1 2.1±0.8 0.84
R [mmHg s/m] 419.0±188.8 453.7±348.2 436.7±302.6 0.68 0.75 0.92
C [mm/mmHg] 0.8±0.3 1.7±1.0 1.7±1.0 0.70* 0.70* 1.00
Table 1.

Quantification of reservoir pressures pres obtained by methods (F), (P1) and (P2) at radial artery in the format of mean±standard deviation based on 63 subjects whereby PP denotes the reservoir pulse pressure, Ap the area of reservoir pressure above diastolic blood pressure, τ the time constant describing the diastolic pressure decay, P the asymptotic blood pressure and a,b = 1/τ the rate constants. Peripheral (area) resistance and compliance, i.e. R and C, were estimated from the rate constants a and b for (P1) and (P2) using flow information. The correlation coefficient r was computed between relevant methods. The statistical significance of the differences between methods was based on a paired t-test with * indicating p < 0.05.

Conclusions: The discrepancies between (F) and (P1), (P2) raise concerns about the validity of the implicit assumptions in pressure-only reservoir pressure separation at the radial artery. Differences in (P1) and (P2) indicate some sensitivity of derived parameters to the algorithm employed.

Open Access
This is an open access article distributed under the CC BY-NC license.

References

[1]J Aguado-Sierra, J Alastruey, J-J Wang, N Hadjiloizou, J Davies, and KH Parker, “Separation of the reservoir and wave pressure and velocity from measurements at an arbitrary location in arteries,”, Proc. Inst. Mech. Eng. Part H J. Eng. Med, Vol. 222, No. 4, 2008, pp. 403-416.
[2]CH Manisty, A Zambanini, KH Parker, JE Davies, DP Francis, J Mayet, SA McG Thom, and AD Hughes, “Differences in the magnitude of wave reflection account for differential effects of amlodipine- versus atenolol-based regimens on central blood pressure: an Anglo- Scandinavian Cardiac Outcome Trial substudy.,”, Hypertension, Vol. 54, No. 4, Oct 2009, pp. 724-30.
[3]J-J Wang, AB O’Brien, NG Shrive, KH Parker, and JV Tyberg, “Time-domain representation of ventricular-arterial coupling as a windkessel and wave system.,”, Am. J. Physiol. Heart Circ. Physiol, Vol. 284, No. 4, Apr 2003, pp. H1358-68.
[4]M Ebner, B Hametner, S Parragh, and S Wassertheurer, “Reservoir Wave Paradigm: An Implementation and Sensitivity Analysis,”, SNE Simul. Notes Eur, Vol. 25, No. 3–4, 2015, pp. 151-156.
[5]B Hametner, S Wassertheurer, AD Hughes, KH Parker, T Weber, and B Eber, “Reservoir and excess pressures predict cardiovascular events in high-risk patients,”, Int. J. Cardiol, Vol. 171, No. 1, 2014, pp. 31-36.
[6]JE Davies, P Lacy, T Tillin, D Collier, JK Cruickshank, DP Francis, A Malaweera, J Mayet, A Stanton, B Williams, KH Parker, SA McG Thom, and AD Hughes, “Excess pressure integral predicts cardiovascular events independent of other risk factors in the conduit artery functional evaluation substudy of Anglo-Scandinavian Cardiac Outcomes Trial.,”, Hypertension, Vol. 64, No. 1, Jul 2014, pp. 60-8.
Journal
Artery Research
Volume-Issue
20 - C
Pages
78 - 79
Publication Date
2017/12/06
ISSN (Online)
1876-4401
ISSN (Print)
1872-9312
DOI
10.1016/j.artres.2017.10.104How to use a DOI?
Open Access
This is an open access article distributed under the CC BY-NC license.

Cite this article

TY  - JOUR
AU  - Michael Ebner
AU  - Kim Parker
AU  - Tom Vercauteren
AU  - Sébastien Ourselin
AU  - Siegfried Wassertheurer
AU  - Alun Hughes
AU  - Bernhard Hametner
PY  - 2017
DA  - 2017/12/06
TI  - P122 CALCULATING RESERVOIR PRESSURE WITH OR WITHOUT FLOW INFORMATION: SIMILARITY AND ALGORITHMIC SENSITIVITY AT RADIAL ARTERY
JO  - Artery Research
SP  - 78
EP  - 79
VL  - 20
IS  - C
SN  - 1876-4401
UR  - https://doi.org/10.1016/j.artres.2017.10.104
DO  - 10.1016/j.artres.2017.10.104
ID  - Ebner2017
ER  -