Gestational Age-Adjusted Reference Ranges for Fetal Left Ventricle Longitudinal Strain by Automated Cardiac Motion Quantification between 24 and 37 Weeks’ Gestation

Abstract

Introduction: The objective of this study was to construct gestational age (GA) based reference values for left ventricle (LV) longitudinal strain in normal fetuses, between 24-37 weeks’ gestation, assessing its feasibility and reproducibility, with automated cardiac motion quantification software (aCMQ-QLab) widely used in postnatal echocardiography. Methods: Prospective study including healthy gravid women with singleton pregnancies and no evidence of fetal structural cardiovascular disease. Fetal echocardiographies were performed between 24 and 37 GA. 2D four-chamber view clips were recorded and LV longitudinal strain was analyzed offline. Intra and interobserver reproducibility between 2 independent observers was evaluated by intraclass correlation coefficients (ICC) and Bland-Altman scatter plots. Regression analysis was used to determine GA adjusted reference ranges and construct nomograms. Results: LV longitudinal strain measurements were feasible in 95.4% of acquisitions. 435 clips were obtained. Intra and interobserver ICC were 0.998 (95% CI 0.997–0.999) and 0.991 (95% CI 0.984–0.995), respectively. Global longitudinal strain, middle and apical LV segments showed progressive decline as gestational age advanced whereas basal segments remained stable. Conclusions: Assessment of LV longitudinal strain by aCMQ-QLab is feasible and reproducible, and normal ranges are provided. Our results offer more information regarding fetal cardiac function assessment with 2D speckle tracking techniques, aiding in the introduction of this software in research practice; encouraging the realization of more studies and probably helping in its future use in clinical practice, allowing longitudinal surveillance of strain without intervendor variability and aiding in follow-up of fetal cardiac conditions before and after birth, as it is the most commonly used software postnatally.

Longitudinal Behavior of Left-Ventricular Strain in Fetal Growth Restriction

“…Our results also showed differences in strain behavior between groups throughout gestation. AGA fetuses had the expected behavior when compared to previously published normal values [ 41 ], remaining stable or decreasing slightly as gestation progressed. In the AGA group, GLO, middle, and apical segments showed progressive decline as GA advanced, whereas the basal segments remained stable throughout gestation.…”

“…Specialized obstetricians with experience in fetal cardiology imaging and placental dysfunction performed image acquisition. Stringent criteria for ultrasound acquisition were followed according to previously published recommendations [ 41 ]. Care was taken to optimize image quality and acquire images with >80 Hz frames per second (fps).…”

“…After evaluating clip quality, a clip that included three or four cardiac cycles was analyzed offline by aCMQ-QLab (Philips Medical Systems, Andover, MA, USA). In order to manually determined the cardiac cycle, a previously published protocol was followed [ 41 ], selecting the endocardial LV border, tracing the LV endocardium, performing a visual check for tracking quality, and manually correcting if necessary.…”

“…Cases with at least two evaluations during pregnancy were included. All measurements of strain evaluation in FGR fetuses were normalized into Z-values, with a mean of 0 and standard deviation of 1, on the basis of previously published reference curves [ 41 ].…”

“…This offers advantages for fetal assessment. Fetal strain evaluated with 2D-STE has demonstrated good reproducibility and feasibility [ 37 , 38 , 39 , 40 , 41 ] with a well-defined step-by-step approach [ 41 ], and normal reference values for fetal LV strain have been previously published [ 41 ], which differ depending on the software or platform used [ 42 , 43 , 44 ], similar to what happens with other echocardiographic tools [ 45 , 46 ], limiting its current use to research but not clinical practice. 2D-STE has previously been described in FGR fetuses [ 47 ]; however, results were heterogeneous and, in some cases, contradictory.…”