Korean Circ J.  2015 Mar;45(2):131-140. 10.4070/kcj.2015.45.2.131.

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

• Kim HJ
• Yoon JH
• Lee EJ
• Oh JH
• Lee JY
• Lee SJ
• Han JW

• KMID: 2297880
• DOI: http://doi.org/10.4070/kcj.2015.45.2.131

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.

Keyword

Ventricular function; Speckle tracking echocardiography; Torsion; Rotation; Child

MeSH Terms

Aging
Child*
Echocardiography
Heart Rate*
Heart Ventricles
Humans
Mechanics*
Multivariate Analysis
Reference Values
Systole
Ventricular Function

Figure

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  Fig. 1 Representative curves of left ventricular (LV) torsion movement. A: LV apical and basal rotation, and twist curves. Positive values express counterclockwise rotation or twist as seen from the apex. During early systole including isovolumetric contraction time, LV twists in opposite direction (early systolic twist, EST) of a dominant LV systolic twist during mid- or late systole. B: LV basal and apical rational velocity (Vr), and peak twist (Vt) and untwist (Vut) velocity curves. Peak twist velocity is observed at around a half of systolic time, whereas peak untwist velocity is seen during early diastolic period. Red arrows indicate the reference point of starting cardiac cycle (Q-wave). AVC: aortic valve closure, MVO: mitral valve opening, ST: systolic time, DT: diastolic time, a: time to peak systolic twist, b: time to peak EST, c: time to peak Vt during systole, d: time to peak Vut during diastole.

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  Fig. 2 Regression plots of early systolic apical (A) and basal rotation (B) with 95% confidence intervals. The apical segment showed clockwise (n=34), counterclockwise (n=27), or no rotation (n=3) during early systole, which changed more clockwise with increasing age (A). In contrast, the basal segment showed early systolic counterclockwise rotation in all subject, which did not change significantly with aging (B). NS: not significant.

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  Fig. 3 Regression plot of early systolic torsion (EStor) with 95% confidence interval. All showed negative values of Estor, which were in opposite direction of the dominant left ventricular systolic twist (positive value) during mid- and late systole. NS: not significant.

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  Fig. 4 Regression plots of apical and basal rotation normalized by left ventricular length with 95% confidence interval. An age related decrease was observed.

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  Fig. 5 Regression plot of the peak left ventricular (LV) torsion with 95% confidence interval, which decreased with increasing age.

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  Fig. 6 Regression plots of peak twist and untwisting velocities with 95% confidence intervals. When normalized by left ventricular length, peak twist and untwisting velocities decreased with increasing age.

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