Effects of frame rate on two-dimensional speckle tracking-derived measurements of myocardial deformation in premature infants.

Background: Frame rate (FR) of image acquisition is an important determinant of the reliability of 2-dimensional speckle tracking echocardiography (2DSTE)-derived myocardial strain. Premature infants have relatively high heart rates (HR). The aim was to analyze the effects of varying FR on the reproducibility of 2DSTE-derived right ventricle (RV) and left ventricle (LV) longitudinal strain (LS) and strain rate (LSR) in premature infants.

Methods: RV and LV LS and LSR were measured by 2DSTE in the apical four-chamber view in 20 premature infants (26 ± 1 weeks) with HR 163 ± 13 bpm. For each subject, 4 sets of cine loops were acquired at FR of <90, 90-110, 110-130, and >130 frames/sec. Two observers measured LS and LSR. Inter- and intra-observer reproducibility was assessed using Bland-Altman analysis, coefficient of variation, and linear regression.

Results: Intra-observer reproducibility for RV and LV LS was higher at FR >110 frames/sec, and optimum at FR >130 frames/sec. The highest inter-observer reproducibility for RV and LV LS were at FR >130 and >110 frames/s, respectively. The highest reproducibility for RV and LV systolic and early diastolic LSR was at FR >110 frames/sec. FR/HR ratio >0.7 frames/sec per bpm yielded optimum reproducibility for RV and LV deformation imaging.

Conclusions: The reliability of 2DSTE-derived RV and LV deformation imaging in premature infants is affected by the FR of image acquisition. Reproducibility is most robust when cine loops are obtained with FR/HR ratio between 0.7 and 0.9 frames/sec per bpm, which likely results from optimal myocardial speckle tracking and mechanical event timing.