title: Specific left ventricular twist-untwist mechanics during exercise in children.
abstract: BACKGROUND
  In adults, left ventricular (LV) systolic twist is an important factor that determines LV filling, both at rest and during exercise. In children, lower LV twist has been demonstrated at rest, but its adaptation during exercise and its functional consequences on LV filling are unknown.
  
  
  METHODS
  Using speckle-tracking echocardiography, LV twist-untwist mechanics were studied in 25 children (aged 10-12 years) and 20 young adults (aged 18-44 years) at rest and during three exercise workloads performed at 20%, 30%, and 40% of their maximal aerobic power.
  
  
  RESULTS
  At rest, LV twist was lower in children, because of a higher temporal dispersion of peak rotation between base and apex. During exercise, the increase of basal rotation was blunted in children compared with adults (-6.7 ± 2.7° vs -9.0 ± 2.0° at 40% of maximal aerobic power, P < .05). Consequently, LV twist increased to a lesser extent (13.0 ± 5.0° vs 15.8 ± 4.5° at 40% of maximal aerobic power, P < .05). The increase in LV untwisting rates during exercise was also lower in children, leading to a lower percentage of untwisting during early diastole (8 ± 8% vs 29 ± 20% at 40% of maximal aerobic power, P < .001). Consequently, during early diastole, the normal timing of diastolic events observed in young adults, with untwist occurring before radial displacement, was blunted in children. Nevertheless, children exhibited normal LV filling due to higher diastolic radial and longitudinal strain rates.
  
  
  CONCLUSIONS
  Twist-untwist mechanics may evolve with advancing age. In children, early diastolic LV untwisting appears to be less important than in adults. Their better LV intrinsic myocardial relaxation may ensure adequate LV filling during exercise without dependence on the additional effect of suction resulting from LV energy recoil.
authors: EA 4488-Activité Physique-Muscle-Santé, Université Lille Nord de France, Faculté des Sciences du Sport et de l'Education Physique, Lille, France.
authors: Julien
authors: J
authors: Boissière
authors: Claire
authors: C
authors: Maufrais
authors: Georges
authors: G
authors: Baquet
authors: Iris
authors: I
authors: Schuster
authors: Michel
authors: M
authors: Dauzat
authors: Grégory
authors: G
authors: Doucende
authors: Philippe
authors: P
authors: Obert
authors: Serge
authors: S
authors: Berthoin
authors: Stéphane
authors: S
authors: Nottin
mesh_terms: D000293:Adolescent; D000328:Adult; D000375:Aging / Q000502:physiology*; D002648:Child; D004452:Echocardiography / Q000379:methods*; D015444:Exercise / Q000502:physiology*; D005260:Female; D005602:France; D006352:Heart Ventricles / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D012399:Rotation; D016277:Ventricular Function, Left / Q000502:physiology*; D055815:Young Adult
keywords: AVC; Aortic valve closure; Children; Exercise; Exercise at 20% of maximal aerobic power; Exercise at 30% of maximal aerobic power; Exercise at 40% of maximal aerobic power; IVRT; Isovolumetric relaxation time; LV; Left ventricle; Left ventricular; SR; STE; Speckle-tracking echocardiography; Strain rate; Untwisting angle during isovolumetric relaxation time; W1; W2; W3; °UT(IVRT)