Beat-to-beat variation in pulse wave velocity during breathing maneuvers.
OBJECTIVE
Thoracic pulse wave velocity (PWV) variation due to modulated trans-mural pressure (TMP) may indicate mechanical properties of the aorta. Our aim was to measure beat-to-beat thoracic PWV and TMP to observe its normal variation during respiratory maneuvers.


METHODS
We validated PWV measurements from a real-time velocity projection MRI scan in a pulsatile phantom. A volunteer study showed inter-scan repeatability of steady-state PWV, and observed PWV variation when performing Mueller and Valsalva maneuvers. Synchronized to the real-time projection velocity data, TMP was measured using a mouth piece and pressure sensor arrangement monitoring the intra-thoracic pressure and a single arterial pressure measurement.


RESULTS
In the phantom, beat-to-beat PWV derived from real-time projection (5.33 ± 0.32 m s(-1) ) agreed well with experimentally derived PWV using ultrasound probes (5.72 ± 0.50 m s(-1) ). The within-subject PWV variation between scans was 0.28 m s(-1) . Volunteers' PWVs increased during Mueller maneuver (TMP increase of 14.67 ± 10.69 mmHg) by 32% (P < 0.001), and during Valsalva maneuver (TMP decrease of TMP = 17.01 ± 12.91 mmHg), PWV response were inconsistent with an average increase of 14% (P < 0.05).


CONCLUSIONS
Gating TMP to beat-to-beat PWV allows insight into how aortic stiffness varies with strain. However, quantifying nonlinear arterial stiffness requires real-time arterial pressure measurement.
Division of Imaging Sciences and Biomedical Engineering, King's College London, St. Thomas' Hospital, London, UK.
Nicholas R
NR
Gaddum
Tobias
T
Schaeffter
Martin
M
Bührer
Marcel
M
Rutten
Lorna
L
Smith
Philip J
PJ
Chowienczyk
Philipp B J
PB
Beerbaum
D000328:Adult; D001013:Aorta, Thoracic / Q000033:anatomy & histology* / Q000502:physiology*; D001783:Blood Flow Velocity; D001794:Blood Pressure; D064368:Healthy Volunteers; D018056:Hemorheology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D011673:Pulsatile Flow; D012039:Regional Blood Flow; D014636:Valsalva Maneuver
Mueller; Valsalva; magnetic resonance; pulse wave velocity; real time phase contrast; respiratory maneuver