Novel magnetic resonance wave intensity analysis in pulmonary hypertension
Michael A Quail
0
1
Daniel S Knight
1
Jennifer A Steeden
1
Andrew Taylor
0
1
Vivek Muthurangu
0
1
0
Great Ormond Street Hospital for Children
,
London
,
UK
1
Centre for Cardiovascular Imaging, Institute of Cardiovascular Science
,
London
,
UK
From 17th Annual SCMR Scientific Sessions New Orleans, LA, USA. 16-19 January 2014
-
Background
In pulmonary arterial hypertension (PH), abnormal wave
reflections play an important part in pathophysiology
and can be assessed using wave intensity analysis
(WIA). However, conventionally this technique requires
simultaneous invasive measurement of pulmonary artery
pressure and velocity. Therefore, we have developed a
novel non-invasive technique that uses high
temporalresolution phase-contrast MR (PCMR) flow and area
data to perform WIA. The aim of this study was to
establish any differences in wave reflections between
patients with PH and healthy volunteers.
Methods
Right PA volume flow and area curves were obtained in
15 patients with PH (mean SD, age 52 13 years)
and 10 healthy controls (age 45 11 years) using a
retrospectively gated, respiratory navigated, golden-angle,
high TR, PCMR sequence. The right PA was used to
avoid the through plane motion in the main PA. All
patients also underwent right heart cardiac
catheterization for pressure and vascular resistance (PVR)
measureTable 1 Data Table, Pulmonary Hypertension and Healthy Controls
ment within 30days (mean 11days) and had serum brain
natriuretic peptide (BNP) measured. Wave speed was
determined in the right PA using the single slice Q-A
method. WIA was derived in terms of volume flow and
area changes.
Results
There were significant differences in WIA between cases
and controls (Table 1 Figure 1). Wave speed was higher
in PH than controls in keeping with reduced arterial
compliance (p = 0.0001). A backwards compression wave
(BCW) was observed in all patients with PH (Figure 1C),
but was absent in all control patients (p < 0.0001).
Conversely a backwards expansion wave was seen in
normal controls but not in PH. Average PVR and PA mean
arterial pressure (MAP) were 612 298 ARU and 43
12 mmHg respectively. There was a significant
correlation between MAP and the duration of the BCW
(R = 0.62, p = 0.01) and also the ratio of the magnitude
of the forward (FCW) and backwards compression waves
(R = -0.57, p = 0.03). PVR was independently associated
with the acceleration time (AT, Figure 1A) (b = -1.42,
Wave Speed (m/s)
Backwards Compression Wave (BCW)
Backwards Expansion Wave (BEW)
Acceleration Time (ms)
Pulmonary Hypertension n = 15
1Centre for Cardiovascular Imaging, Institute of Cardiovascular Science,
London, UK
Full list of author information is available at the end of the article
Figure 1 Example flow curves from a PH patient (A) and a healthy control (B), demonstrating abnormal contour in PH. Net wave
intensity plots from PH (C) and healthy control (D) showing the presence of a backwards compression wave (BCW). AT, Acceleration time.
p = 0.005) and the time of onset of the BCW (b = 0.95,
p = 0.039) by multiple linear regression analysis (Model,
R = 0.74). The ratio of the FCW and BCW correlated
significantly with serum BNP (R = 0.63, p = 0.017).
Conclusions
We have demonstrated that it is possible to assess
abnormal hemodynamic abnormalities in PH using CMR based
WIA. Specifically, patients with PH have an abnormal
backwards-traveling compression wave, which probably
arises from the narrowed distal vasculature, augmenting
pressure and reducing flow. Furthermore, there is also loss
of the normal backwards expansion wave that is thought
to increase flow in the pulmonary artery. Importantly, we
have shown that WIA indices correlate strongly with
pressure, vascular resistance and serum markers of disease
severity, and therefore show promise as a diagnostic tool
for PH.
(...truncated)