title: Non-invasive measurement using cardiovascular magnetic resonance of changes in pulmonary artery stiffness with exercise.
abstract: BACKGROUND
  Exercise stress tests are commonly used in clinical settings to monitor the functional state of the heart and vasculature. Large artery stiffness is one measure of arterial function that can be quantified noninvasively during exercise stress. Changes in proximal pulmonary artery stiffness are especially relevant to the progression of pulmonary hypertension (PH), since pulmonary artery (PA) stiffness is the best current predictor of mortality from right ventricular failure.
  
  
  METHODS
  Cardiovascular magnetic resonance (CMR) was used to investigate the effect of exercise stress on PA pulse wave velocity (PWV) and relative area change (RAC), which are both non-invasive measures of PA stiffness, in healthy subjects. All 21 subjects (average age 26 ± 4 years; 13 female and 8 male) used a custom-made MR-compatible stepping device to exercise (two stages of mild-to-moderate exercise of 3-4 min duration each) in a supine position within the confines of the scanner. To measure the cross-sectional area and blood flow velocity in the main PA (MPA), two-dimensional phase-contrast (2D-PC) CMR images were acquired. To measure the reproducibility of metrics, CMR images were analyzed by two independent observers. Inter-observer agreements were calculated using the intraclass correlation and Bland-Altman analysis.
  
  
  RESULTS
  From rest to the highest level of exercise, cardiac output increased from 5.9 ± 1.4 L/min to 8.2 ± 1.9 L/min (p < 0.05), MPA PWV increased from 1.6 ± 0.5 m/s to 3.6 ± 1.4 m/s (p < 0.05), and MPA RAC decreased from 0.34 ± 0.11 to 0.24 ± 0.1 (p < 0.05). While PWV also increased from the first to second exercise stage (from 2.7 ± 1.0 m/s to 3.6 ± 1.4 m/s, p < 0.05), there was no significant change in RAC between the two exercise stages. We found good inter-observer agreement for quantification of MPA flow, RAC and PWV.
  
  
  CONCLUSIONS
  These results demonstrate that metrics of MPA stiffness increase in response to acute moderate exercise in healthy subjects and that CMR exercise stress offers great potential in clinical practice to noninvasively assess vascular function.
authors.affiliation: Department of Biomedical Engineering, University of Wisconsin-Madison, Engineering Centers Building, 1550 Engineering Drive, Madison, WI, 53706, USA. forouzan@wisc.edu.
authors.forename: Omid
authors.initials: O
authors.lastname: Forouzan
authors.affiliation: Department of Biomedical Engineering, University of Wisconsin-Madison, Engineering Centers Building, 1550 Engineering Drive, Madison, WI, 53706, USA. jaredwarczytowa@gmail.com.
authors.forename: Jared
authors.initials: J
authors.lastname: Warczytowa
authors.affiliation: Department of Biomedical Engineering, University of Wisconsin-Madison, Engineering Centers Building, 1550 Engineering Drive, Madison, WI, 53706, USA. owieben@wisc.edu.|Department of Medical Physics, Wisconsin Institutes for Medical Research, 1111 Highland Avenue, Madison, WI, 53705-2275, USA. owieben@wisc.edu.|Department of Radiology, University of Wisconsin, School of Medicine and Public Health, E3/366 Clinical Science Center, 600 Highland Avenue, Madison, WI, 53792-3252, USA. owieben@wisc.edu.
authors.forename: Oliver
authors.initials: O
authors.lastname: Wieben
authors.affiliation: Department of Radiology, University of Wisconsin, School of Medicine and Public Health, E3/366 Clinical Science Center, 600 Highland Avenue, Madison, WI, 53792-3252, USA. cfrancois@uwhealth.org.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: François
authors.affiliation: Department of Biomedical Engineering, University of Wisconsin-Madison, Engineering Centers Building, 1550 Engineering Drive, Madison, WI, 53706, USA. chesler@engr.wisc.edu.
authors.forename: Naomi C
authors.initials: NC
authors.lastname: Chesler
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D001783:Blood Flow Velocity; D004867:Equipment Design; D015444:Exercise; D005080:Exercise Test; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008297:Male; D015588:Observer Variation; D056888:Patient Positioning; D011237:Predictive Value of Tests; D011651:Pulmonary Artery / Q000502:physiology*; D011652:Pulmonary Circulation; D063177:Pulse Wave Analysis / Q000295:instrumentation / Q000379:methods*; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D016683:Supine Position; D059289:Vascular Stiffness; D055815:Young Adult