Normal Left Ventricular Torsion Mechanics in Healthy Children: Age Related Changes of Torsion Parameters Are Closely Related to Changes in Heart Rate

ABSTRACT

BACKGROUND AND OBJECTIVES: This study was aimed at assessing left ventricular torsion (LVtor) mechanics using speckle tracking echocardiography (STE), establishing normal reference values of principal LVtor parameters, and analyzing the age-related changes in normal children. SUBJECTS AND METHODS: Eighty children (aged 3 months to 15 years) with normal cardiac function and rhythm were recruited. LVtor parameters including rotations, twist and untwist, torsion, and their rate indices were measured using STE. Age and heart rate related changes of the parameters were analyzed. RESULTS: Speckle tracking echocardiography analyses for LVtor parameters had excellent reliability in 64 of 80 subjects (80%) (intraclass correlation coefficients; 0.93-0.97). Early systolic twist (EST) motions (-8.4--0.1degrees) were observed in all subjects during an early 20+/-7% of systolic time intervals. The peak systolic twist and torsion were 17.0+/-6.5degrees and 2.9+/-1.3degrees/cm, respectively. The peak twist velocity was recorded at 51+/-13% of systolic time and the peak untwist velocity at 13.8+/-11.5% of diastolic time intervals. Multivariate analysis showed that heart rate change was an independent predictor of changes in torsion parameters; significantly decreasing LV length-normalized apical and basal rotation, torsion, and twist and untwist rate with increasing age. Isovolumetric recoil rate was independent of change in age and heart rate. CONCLUSION: Left ventricle showed unique torsion mechanics in children with EST, torsion, and untwists. Heart rate was an independent predictor of the change in torsion parameters with aging.