Background:
Pathological pulmonary wave reflections (WR) are a potential hemodynamic biomarker for pulmonary hypertension (PH). WR can be quantified using wave intensity analysis (WIA), typically utilizing simultaneous invasive pressure and velocity measurements. In this study we reformulated WIA to use CMR area and flow to measure reflections non-invasively. We hypothesized that this method could detect differences in WR in PH patients compared to healthy controls and could also differentiate certain PH subtypes.
Methods:
20 patients with PH (35% CTEPH), mean age 54years (75% female) and 10 healthy controls, 47years (60% female) were recruited. Branch pulmonary artery (PA) flow volume (Q) and area curves (A) were used to measure wave intensity (
dI
), defined as,
dI
=[[Unable to Display Character: ∆]]Ax[[Unable to Display Character: ∆]]Q and
dI
±
=±
c
/4 [[[Unable to Display Character: ∆]]A± [[Unable to Display Character: ∆]]Q/
c
]
2
, where
c
=wave-speed. Data were acquired using a retrospectively gated, respiratory navigated, golden-angle, 10.5ms temporal resolution, phase-contrast MR sequence. All patients also underwent right heart cardiac catheterization for pressure and vascular resistance (PVR) measurement, median interval 6 days (IQR 2-11days). The presence of proximal clot in CTEPH patients was determined from contemporaneous CT/angiographic data.
Results:
A backwards-travelling compression wave (BCW) was present in both left and right PAs of all PH patients, but was absent in all controls (
p
=6e
-8
). A backwards-travelling expansion/suction wave was present in the 19/20 branch PAs of controls, and only 4/40 PAs in patients (
p
< 0.0001). The area under the BCW was associated with a sensitivity of 100% (95% CI 63-100%) and specificity of 91% (95% CI 75-98%) for the presence of clot in the proximal pulmonary arteries of patients with CTEPH.
Conclusions:
Noninvasive pulmonary WIA accurately delineates pulmonary vascular health and disease. The main findings of this study were: i) There was a significant difference in WIA metrics between patients and controls, in particular, the presence of a BCW was specifically associated with the presence of PH; and ii) The magnitude of the BCW area showed discriminatory capacity for the presence of proximal PA clot in patients with CTEPH. We believe that these results demonstrate that WIA could be used in the non-invasive assessment of PH.
Novel magnetic resonance wave intensity analysis in pulmonary hypertension