Fetal and Neonatal Diastolic Myocardial Strain Rate: Normal Reference Ranges and Reproducibility in a Prospective, Longitudinal Cohort of Pregnancies.

BACKGROUND: Normative fetal diastolic strain rate values have not been comprehensively reported. The aims of this study were to report normative data for diastolic strain rate parameters across gestation and upon delivery, determine the effect of advancing gestational age on these measures, and compare interobserver variability at multiple gestational age time points. METHODS: Sixty gravid women were enrolled before 20 weeks' gestation. The following measures were obtained by two blinded observers at five time points across gestation and at 4 to 8 weeks' postnatal age: global left ventricular circumferential strain rate peak E and A waves, global left and right ventricular longitudinal strain rate peak E and A waves, and mitral and tricuspid valve E/A ratios. Reproducibility was assessed using intraclass correlation and Bland-Altman analysis. Least square means analysis was used to evaluate for changes across gestational age. RESULTS: Left ventricular longitudinal and circumferential diastolic strain rate values decreased across gestation, while right ventricular longitudinal values remained stable. With delivery, left ventricular values remained fairly stable, while right ventricular values increased. Intraclass correlations for diastolic strain rate values were 0.68 to 0.94 at ≥24 weeks' gestation and 0.25 to 0.82 for values at 20 to 21 weeks' gestation. Intraclass correlations ranged from 0.49 to 0.90 for mitral valve and tricuspid valve E/A ratios across gestation. CONCLUSIONS: Fetal measures of diastolic strain rate have acceptable reproducibility after 24 weeks' gestation. The described changes across gestation likely reflect intrinsic myocardial adaptation to loading conditions. These reference ranges can be used to assess effects of various disease states on fetal myocardial deformation.

Longitudinal Changes and Interobserver Variability of Systolic Myocardial Deformation Values in a Prospective Cohort of Healthy Fetuses across Gestation and after Delivery.

BACKGROUND: Normative data for fetal myocardial deformation values have not been comprehensively described in a longitudinal cohort. The effect of gestational age on these values and on interobserver variability require further investigation. METHODS: Sixty gravid women were prospectively enrolled before 20 weeks' gestation. The following measures were obtained by two blinded observers at five time points across gestation and also at 4 to 8 weeks' postnatal age: global circumferential strain and strain rate, global longitudinal left ventricular strain and strain rate, global longitudinal right ventricular strain and strain rate, and left and right ventricular myocardial performance indices. Optimal myocardial visualization and frame rate (≥100 frames/sec) were ensured. RESULTS: For gestational age groups ≥24 weeks, intraclass correlation coefficients between observers were >0.70 for all measures and >0.85 for the majority of measures of myocardial deformation. At 20 to 21 weeks' gestation, intraclass correlation coefficients were 0.35 to 0.52 for longitudinal measures and 0.74 to 0.82 for circumferential measures. Myocardial performance index intraclass correlation coefficients were <0.80 at all time points and <0.70 for most time points. Global longitudinal left ventricular strain and global circumferential strain values remained stable across gestational age groups. Global longitudinal right ventricular strain values remained stable across gestation and increased after birth. Global circumferential strain rate, global longitudinal left ventricular strain rate, and global longitudinal right ventricular strain rate decreased from 20 to 21 weeks' gestation to the remainder of gestation and then remained stable until delivery. Upon delivery, global circumferential strain rate and global longitudinal left ventricular strain rate decreased, and global longitudinal right ventricular strain rate increased. CONCLUSIONS: Interobserver variability of fetal strain and strain rate measured at ≥24 weeks' gestation was lower in comparison with values obtained at 20 to 21 weeks' gestation and lower in comparison with left ventricular and right ventricular myocardial performance indices using the described protocol. Gestational changes in fetal myocardial deformation values likely reflect changes in preload and/or afterload on the fetal heart.