title: Non-invasive evaluation of pulmonary arterial blood flow and wall shear stress in pulmonary arterial hypertension with 3D phase contrast magnetic resonance imaging.
abstract: BACKGROUND
  Recently, time-resolved 3D phase contrast magnetic resonance imaging (4D-flow) allows flow dynamics in patients with pulmonary arterial hypertension to be measured. Abnormal flow dynamics, such as vortex blood flow pattern in the pulmonary artery (PA), may reflect progression of pulmonary arterial hypertension (PAH). Some reports suggested that abnormal blood flow parameters including wall shear stress (WSS) could be markers of PAH. However, it was not fully assessed clinical usefulness of these variables. We aimed to assess whether these flow dynamic parameters, such as vortex formation time (VFT) and WSS, were associated with right ventricular (RV) function.
  
  
  RESULTS
  Fifteen subjects, nine with PAH and six healthy volunteers, underwent 4D-flow. Differences of Blood flow patterns, blood flow velocities and WSS between PAH patients and healthy volunteers were evaluated. We also assessed the association between VFT, WSS and RV function in PAH patients. Both vortex blood flow patterns and early systolic retrograde flow in the main PA were observed in all patients with PAH. The PA flow velocities and WSS in patients with PAH were lower than those in healthy volunteers, but that blood flow volumes in the MPA, RPA and LPA and SV in the MPA were broadly comparable between the groups. The mean VFT was 35.0 ± 16.6 % of the cardiac cycle. The VFT significantly correlated with RV ejection fraction, RV end systolic volume, and RV end systolic volume index (RVEF = 75.1 + (-85.7)·VFT, p = 0.003, RVESV = 12.4 + 181.8·VFT, p = 0.037 and RVESVI = 10.6 + 114.8·VFT, p = 0.038, respectively) in PAH patients, whereas WSS did not correlate with RV function.
  
  
  CONCLUSIONS
  We confirmed that abnormal blood flow dynamics, including the vortex formation and the early onset of retrograde flow, low WSS in the PA were characteristics of PAH. The VFT may be associated with right ventricular dysfunction, whereas WSS was not. Our results suggest that 4D-flow is an effective means of detecting right heart failure as well as diagnosing PAH.
  
  
  BACKGROUND
  https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi. Unique identifier: UMIN000011128.
authors.affiliation: Department of Clinical Pharmacology and Therapeutics, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192 Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Odagiri
authors.affiliation: Department of Clinical Pharmacology and Therapeutics, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192 Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Inui
authors.affiliation: Department of Clinical Pharmacology and Therapeutics, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192 Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Hakamata
authors.affiliation: Department of Internal Medicine II, Hamamatsu University School of Medicine, Hamamatsu, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Inoue
authors.affiliation: Department of Internal Medicine II, Hamamatsu University School of Medicine, Hamamatsu, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Suda
authors.affiliation: Department of Radiology, Hamamatsu University School of Medicine, Hamamatsu, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Takehara
authors.affiliation: Department of Radiology, Hamamatsu University School of Medicine, Hamamatsu, Japan.
authors.forename: Harumi
authors.initials: H
authors.lastname: Sakahara
authors.affiliation: Department of Radiology, Hamamatsu University School of Medicine, Hamamatsu, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Sugiyama
authors.affiliation: Department of Radiology, Stanford University, Palo Alto, CA USA.
authors.forename: Marcus T
authors.initials: MT
authors.lastname: Alley
authors.affiliation: GE Healthcare Japan, Hino, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Wakayama
authors.affiliation: Department of Clinical Pharmacology and Therapeutics, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192 Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Watanabe
keywords: 4D-flow; Diagnosis; Magnetic resonance imaging; Pulmonary artery; Right ventricle