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

Michael Ebner; Kim Parker; Tom Vercauteren; Sébastien Ourselin; Siegfried Wassertheurer; Alun Hughes; Bernhard Hametner

doi:10.1016/j.artres.2017.10.104

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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.2017.10.104 How 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	p_res (F)	p_res (P1)	p_res (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^*
A_p [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 p_res 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, A_p 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.

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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.

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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.2017.10.104 How to use a DOI?
Open Access: This is an open access article distributed under the CC BY-NC license.

Cite this article

ris enw bib

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  -

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