title: Novel insight into the detailed myocardial motion and deformation of the rodent heart using high-resolution phase contrast cardiovascular magnetic resonance.
abstract: BACKGROUND
  Phase contrast velocimetry cardiovascular magnetic resonance (PC-CMR) is a powerful and versatile tool allowing assessment of in vivo motion of the myocardium. However, PC-CMR is sensitive to motion related artifacts causing errors that are geometrically systematic, rendering regional analysis of myocardial function challenging. The objective of this study was to establish an optimized PC-CMR method able to provide novel insight in the complex regional motion and strain of the rodent myocardium, and provide a proof-of-concept in normal and diseased rat hearts with higher temporal and spatial resolution than previously reported.
  
  
  METHODS
  A PC-CMR protocol optimized for assessing the motion and deformation of the myocardium in rats with high spatiotemporal resolution was established, and ten animals with different degree of cardiac dysfunction underwent examination and served as proof-of-concept. Global and regional myocardial velocities and circumferential strain were calculated, and the results were compared to five control animals. Furthermore, the global strain measurements were validated against speckle-tracking echocardiography, and inter- and intrastudy variability of the protocol were evaluated.
  
  
  RESULTS
  The presented method allows assessment of regional myocardial function in rats with high level of detail; temporal resolution was 3.2 ms, and analysis was done using 32 circumferential segments. In the dysfunctional hearts, global and regional function were distinctly altered, including reduced global peak values, increased regional heterogeneity and increased index of dyssynchrony. Strain derived from the PC-CMR data was in excellent agreement with echocardiography (r = 0.95, p < 0.001; limits-of-agreement -0.02 ± 3.92%strain), and intra- and interstudy variability were low for both velocity and strain (limits-of-agreement, radial motion: 0.01 ± 0.32 cm/s and -0.06 ± 0.75 cm/s; circumferential strain: -0.16 ± 0.89%strain and -0.71 ± 1.67%strain, for intra- and interstudy, respectively).
  
  
  CONCLUSIONS
  We demonstrate, for the first time, that PC-CMR enables high-resolution evaluation of in vivo circumferential strain in addition to myocardial motion of the rat heart. In combination with the superior geometric robustness of CMR, this ultimately provides a tool for longitudinal studies of regional function in rodents with high level of detail.
authors.affiliation: Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Kirkeveien 166, N-0407, Oslo, Norway. ekespe@medisin.uio.no.
authors.forename: Emil K S
authors.initials: EK
authors.lastname: Espe
authors.forename: Jan Magnus
authors.initials: JM
authors.lastname: Aronsen
authors.forename: Kristine
authors.initials: K
authors.lastname: Skårdal
authors.forename: Jürgen E
authors.initials: JE
authors.lastname: Schneider
authors.forename: Lili
authors.initials: L
authors.lastname: Zhang
authors.forename: Ivar
authors.initials: I
authors.lastname: Sjaastad
mesh_terms: D000818:Animals; D016477:Artifacts; D001696:Biomechanical Phenomena; D004195:Disease Models, Animal; D008279:Magnetic Resonance Imaging; D008297:Male; D009200:Myocardial Contraction; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000503:physiopathology; D011237:Predictive Value of Tests; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D013997:Time Factors; D014463:Ultrasonography
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