Postsystolic shortening by myocardial deformation imaging as a sign of cardiac adaptation to pressure overload in fetal growth restriction.

BACKGROUND: Fetal growth restriction (FGR) is associated with global adverse cardiac remodeling in utero and increased cardiovascular mortality in adulthood. Prenatal myocardial deformation has not been evaluated in FGR to date. We aimed to evaluate prenatal cardiac remodeling comprehensively in FGR including myocardial deformation imaging. METHODS AND RESULTS: Echocardiography was performed in 37 consecutive FGR (defined as birthweight <10th centile) and 37 normally grown fetuses. A comprehensive fetal echocardiography was performed including tissue Doppler and 2-dimensional-derived strain and strain rate. Postnatal blood pressure measurement at 6 months of age was also performed. FGR cases showed signs of more globular hearts with decreased longitudinal motion (left systolic annular peak velocity: controls mean 6 cm/s [SD 1.2] versus FGR 5.3 [1]) and diastolic dysfunction (isovolumic relaxation time: controls 44 ms [6] versus FGR 52 [9]). Peak strain and strain rate values of the left ventricle were not significantly different; however, a postsystolic shortening in the basal segment of the septal ventricular wall was observed in 57% of the FGR cases and in none of controls (P<0.001). FGR cases with postsystolic shortening had absence of a hypertrophic response, a poorer perinatal outcome (lower gestational age and birthweight, containing all cases of perinatal mortality [8%]), and higher values of blood pressure. CONCLUSIONS: Myocardial deformation imaging revealed a postsystolic shortening in 57% of FGR, which supports increased pressure overload as a mechanism for cardiovascular programming in FGR. Postsystolic shortening was associated with severity and with higher blood pressure postnatally.

Feasibility and reproducibility of a standard protocol for 2D speckle tracking and tissue Doppler-based strain and strain rate analysis of the fetal heart.

PURPOSE: Assessment of cardiac function in the fetal heart is challenging because of its small size and high heart rate, restricted physical access to the fetus, and impossibility of fetal ECG recording. We aimed to standardize the acquisition and postprocessing of fetal echocardiography for deformation analysis and to assess its feasibility, reproducibility, and correlation for longitudinal strain and strain rate measurements by tissue Doppler imaging (TDI) and 2D speckle tracking (2D-strain) during pregnancy. METHODS: Echocardiography was performed in 56 fetuses. 2D and color TDI in apical or basal four-chamber views were recorded for subsequent analysis. Caution was taken to achieve a frame rate >70 Hz for speckle tracking and >150 Hz for TDI analysis. For each acquisition, 7.5 s of noncompressed data were stored in cine loop format and analyzed offline. Since fetal ECG information is by definition not available, aortic valve closure was marked from aortic flow and the onset of each cardiac cycle was manually indicated in the 2D images. Sample volume length was standardized at the minimum size. Two observers measured the left and right ventricular peak systolic longitudinal strain and strain-rate. RESULTS: Strain and strain rate measurements were feasible in 93% of the TDI and 2D-strain acquisitions. The mean time spent on analyzing TDI images was 18 min, with an intraclass agreement coefficient of 0.86 (95% CI 0.77-0.92), 0.83 (95% CI 0.72-0.90), 0.96 (95% CI 0.93-0.98), and 0.86 (95% CI 0.76-0.92) for basal left and right free wall peak systolic strain and strain rate, respectively. Agreement between observers using tissue Doppler also showed high reliability. The mean time spent for 2D-strain analysis was 15 min, with an intraclass agreement coefficient of 0.97 (95% CI 0.95-0.98), 0.94 (95% CI 0.89-0.96), 0.96 (95% CI 0.93-0.98), and 0.84 (95% CI 0.73-0.90) for basal left and right free wall peak systolic strain and strain rate, respectively. Agreement between observers also showed a high reliability that was similar for TDI and 2D-strain. There was a weak correlation between TDI and 2D-strain measurements. CONCLUSIONS: A standard protocol with fixed acquisition and processing settings, including manual indication of the timing events of the cardiac cycle to correct for the lack of ECG, was feasible and reproducible for the evaluation of longitudinal ventricular strain and strain rate of the fetal heart by TDI as well as 2D-strain analysis. However, both techniques are not interchangeable as the correlation between them is relatively poor.