1.1 COMPARISON OF VARIOUS METHODS FOR THE ESTIMATION FOR AORTIC CHARACTERISTIC IMPEDANCE IN TIME DOMAIN FROM VELOCITY-ENCODED MAGNETIC RESONANCE AND APPLANATION TONOMETRY DATA

DOI

10.1016/j.artres.2013.10.002How to use a DOI?

Abstract

Objectives. To combine cardiovascular magnetic resonance (CMR), which provides accurate and non-invasive evaluation of flow, with applanation tonometry to assess aortic characteristic impedance (Zc) in time domain while comparing six different methods.

Methods. We studied 72 healthy volunteers (31women, age: 42.1 ± 15.3years) who underwent aortic velocity-encoded CMR and carotid applanation tonometry. We developed a method for the superimposition of flow and pressure waveforms as well as semi-automated estimation of temporal Zc based either on magnitude, derivative peaks and early systolic up-slopes ratios or pressure-flow loop. All Zc indices were used to calculate reflection magnitude (RM) as the ratio between backward and forward pressures.

Results. For all methods, Zc was in good agreement with the reference Zc provided in frequency domain and with the theoretical water-hammer Zc, which combines aortic pulse wave velocity and area, and with carotid pulse pressure (table) with a slight superiority for methods based on derivatives peaks and early systolic up-slopes. In addition, only these latter two methods were significantly related to arterial stiffness indices such as tonometric carotid-femoral pulse wave velocity (r = 0.27 and r = 0.25; p < 0.03) and CMR ascending aorta distensibility (r = −0.30 and r = −0.25; p < 0.03). Again these two methods were slightly superior when comparing the derived RM against age (r = 0.68, r = 0.65; p < 0.0001).

Conclusions. The time derivative and up-slopes straightforward computation methods that can be easily integrated in a clinical workflow provides reliable characteristic impedance and reflection magnitude that might enhance CMR usefulness in evaluating aortic left ventricular (LV) pulsatile load and help for further understanding in LV-aortic coupling.

r (p)	Frequency Zc	Water-hammer Zc	Carotid pulse pressure
Peak Zc	0.59 (p < 0.001)	0.52 (p < 0.001)	0.46 (p < 0.001)
95% peak Zc	0.79 (p < 0.001)	0.54 (p < 0.001)	0.32 (p = 0.01)
Inflection point Zc	0.54 (p < 0.001)	0.53 (p < 0.001)	0.47 (p < 0.001)
Derivative peaks Zc	0.84 (p < 0.001)	0.55 (p < 0.001)	0.56 (p < 0.001)
Early systolic up-slopes Zc	0.91 (p < 0.001)	0.51 (p < 0.001)	0.57 (p < 0.001)
Pressure-flow loop Zc	0.76 (p < 0.001)	0.38 (p = 0.001)	0.39 (p < 0.001)

Table

Comparison of aortic characteristic impedance using the 6 time domain methods against the frequency and theoretical references as well as carotid pulse pressure.

Open Access

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

TY  - JOUR
AU  - E. Bollache
AU  - N. Kachenoura
AU  - I. Bargiotas
AU  - A. de Cesare
AU  - M. Bensalah
AU  - A. Redheuil
AU  - E. Mousseaux
PY  - 2013
DA  - 2013/11/11
TI  - 1.1 COMPARISON OF VARIOUS METHODS FOR THE ESTIMATION FOR AORTIC CHARACTERISTIC IMPEDANCE IN TIME DOMAIN FROM VELOCITY-ENCODED MAGNETIC RESONANCE AND APPLANATION TONOMETRY DATA
JO  - Artery Research
SP  - 161
EP  - 161
VL  - 7
IS  - 3-4
SN  - 1876-4401
UR  - https://doi.org/10.1016/j.artres.2013.10.002
DO  - 10.1016/j.artres.2013.10.002
ID  - Bollache2013
ER  -