4.4 FORWARD AND BACKWARD WAVES AT THE AORTIC ROOT: STEADY-STATE AND WAVE RE-REFLECTION CONSIDERATIONS

DOI

10.1016/j.artres.2015.10.023How to use a DOI?

Abstract

Background: The assumption of steady-state oscillation is often overlooked when arterial pressure and flow waveforms are decomposed into backward (P_b) and forward waves (P_f). This has led to various misinterpretations including a significant reflection-free time during early-systole and attribution of the P_f to solely a product of left ventricular contraction and proximal aortic properties.

Methods: Aortic pressure and flow were measured in anesthetized, open-chest dogs (n = 5). Wave reflections were modified with i.v. infusion of methoxamine (MTX) to increase reflections and nitroprusside (NTP) to decrease reflections. In a human sample (n = 226), central pressure and flow were measured using carotid tonometry and phase-contrast MRI, respectively.

Results: Under conditions of baseline and increased reflections in both dogs and humans, peak of the forward wave (FWA) consistently occurred after time of peak flow (P < 0.001). FWA was systematically greater than peak flow multiplied by aortic characteristic impedance (Q_maxZ_c) in dogs (P < 0.01) and humans (P < 0.01). Only when wave reflections were abolished vasoactively (NTP) in dogs was time of FWA and peak flow the same, leading to insignificant differences in FWA and Q_maxZ_c (P = 0.59).

Conclusion: In steady-state, wave reflections set up in previous cardiac cycles, wave re-reflections at the aortic root, and proximal reflections contribute to both the P_f and P_b waves, even during early-systole. Most importantly, peak aortic flow is also determined by aortic input impedance, which includes effects from properties distal of the proximal aorta. Under steady-state conditions, forward wave amplitude and morphology cannot be attributed solely to the LV and proximal aorta.

Open Access

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

TY  - JOUR
AU  - Timothy Phan*
AU  - John Li
AU  - Vandan Panchal
AU  - Amer Syed
AU  - Ejaz Shah
AU  - Julio Chirinos
PY  - 2015
DA  - 2015/11/23
TI  - 4.4 FORWARD AND BACKWARD WAVES AT THE AORTIC ROOT: STEADY-STATE AND WAVE RE-REFLECTION CONSIDERATIONS
JO  - Artery Research
SP  - 44
EP  - 45
VL  - 12
IS  - C
SN  - 1876-4401
UR  - https://doi.org/10.1016/j.artres.2015.10.023
DO  - 10.1016/j.artres.2015.10.023
ID  - Phan*2015
ER  -