Left ventricular rotational mechanics in early infancy: Normal reference ranges and reproducibility of peak values and time to peak values.

INTRODUCTION

Left ventricular cardiac twist and torsion values have been described in premature and term neonates, but not in early infancy. Early and late peak untwist rates and time to peak (TTP) values have not been described in infants.

METHODS

53 term infants were enrolled prospectively. The following parameters were obtained by two blinded observers at 1-2months postnatal age: peak twist and torsion (twist indexed to LV length), peak twist rate and torsion rate, TTP twist, early peak untwist rate, TTP early untwist rate, late peak untwist rate, TTP late untwist rate. Reproducibility was assessed using intraclass correlation and Bland Altman analysis.

RESULTS

Intraclass correlation was ≥0.87 for all peak rotational mechanics values. Measures of TTP values had intraclass correlation (ICC) values ≤0.77, with TTP twist rate demonstrating the lowest ICC (0.69). The only measure which demonstrated significant bias was TTP twist rate. Peak twist demonstrated modest correlation (R=0.52, p<0.001) with global circumferential strain, and no correlation with ejection fraction, global longitudinal strain, or left ventricular myocardial performance index.

CONCLUSIONS

Measurements of rotational mechanics and timing to peak values have acceptable reproducibility. Peak twist, twist rate, and early untwist rate values in early infancy are similar to those reported in premature neonates, and higher than those reported in older children. Twist indexed to LV length (torsion) is lower in early infancy than in premature neonates, but higher than in term neonates.