Beat-to-beat variation in pulse wave velocity during breathing maneuvers
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Abstract
Purpose
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).
Conclusion
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. Magn Reson Med 72:202–210, 2014. © 2013 Wiley Periodicals, Inc.
