title: Left Ventricular Rotational Mechanics in Preterm Infants Less Than 29 Weeks' Gestation over the First Week after Birth.
abstract: BACKGROUND
  There is a paucity of data on left ventricular (LV) rotational physiology, twist, and torsional mechanics in preterm infants. The principal aims of the present study were to assess the feasibility and reproducibility of measuring LV rotation, twist, and torsion in preterm infants (<29 weeks' gestation) using two-dimensional speckle-tracking echocardiography and to examine the changes in those parameters over the first week after birth.
  
  
  METHODS
  This was a prospective observational study involving preterm infants <29 weeks' gestation. Echocardiographic evaluations were performed on days 1, 2, and 5 to 7 after delivery. LV basal and apical rotation, LV twist, LV twist rate (LVTR), and LV untwist rate (LVUTR) were measured from the basal and apical short-axis parasternal views and calculated using two-dimensional speckle-tracking echocardiography. Torsion was also calculated by normalizing LV twist to LV end-diastolic length. One-way repeated-measures analysis of variance was used to compare values across the three time points. Intra- and interobserver reproducibility were assessed using Bland-Altman analysis and the intraclass correlation coefficient.
  
  
  RESULTS
  Fifty-one infants with a mean ± SD gestational age of 26.8 ± 1.5 weeks and a mean birth weight of 945 ± 233 g were included. There was high intra- and interobserver reproducibility for basal and apical rotation, LV twist, and LV torsion, with intraclass correlation coefficients ranging from 0.78 to 0.96 (P < .001 for all). Intra- and interobserver intraclass correlation coefficients for LVTR and LVUTR ranged from 0.70 to 0.88 (P < .001 for all). Apical rotation remained constant over the first week of age in a positive counterclockwise fashion (11.8 ± 5.0° vs 12.1 ± 6.1° vs 11.7 ± 8.3°, P = .92). Basal rotation changed from counterclockwise on day 1 to clockwise on day 7 (median, 5.5° [interquartile range, -0.3° to 8.3°] vs 4.0 [interquartile range, -4.7° to 7.2°] vs -4.5° [interquartile range, -5.8° to -2.3°], P < .001), with resultant net increases in twist and torsion (P < .05). There was no change in LVTR (P = .60), but LVUTR increased across the same time period (P = .01).
  
  
  CONCLUSIONS
  Assessment of twist, LVTR, and LVUTR is feasible in preterm infants, with acceptable reproducibility. There are increases in LV twist and torsion in addition to LVUTR, suggesting changes in LV mechanics during the first week of age.
authors.affiliation: Department of Neonatology, The Rotunda Hospital, Dublin, Ireland.
authors.forename: Adam
authors.initials: A
authors.lastname: James
authors.affiliation: Department of Neonatology, The Rotunda Hospital, Dublin, Ireland.
authors.forename: John David
authors.initials: JD
authors.lastname: Corcoran
authors.affiliation: The Labatt Family Heart Centre, The Hospital for Children, Toronto, Ontario, Canada.
authors.forename: Luc
authors.initials: L
authors.lastname: Mertens
authors.affiliation: Department of Pediatric Cardiology, Our Lady's Children's Hospital, Crumlin, Dublin, Ireland.
authors.forename: Orla
authors.initials: O
authors.lastname: Franklin
authors.affiliation: Department of Neonatology, The Rotunda Hospital, Dublin, Ireland; Department of Pediatrics, The Royal College of Surgeons in Ireland, Dublin, Ireland. Electronic address: afif@physicians.ie.
authors.forename: Afif
authors.initials: A
authors.lastname: El-Khuffash
mesh_terms: D004452:Echocardiography / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D005865:Gestational Age; D006352:Heart Ventricles / Q000000981:diagnostic imaging*; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D012399:Rotation; D016277:Ventricular Function, Left / Q000502:physiology*
keywords: Neonate; Preterm; Speckle-tracking echocardiography; Torsion; Twist