Assessment of Atrial Size, Shape, and Contractility in Growth-Restricted and Small-for-Gestational-Age Fetuses

Objectives - The size, shape, and contractility of the heart's atrial chambers have not been evaluated in fetuses with growth restriction (FGR) or who are small-for-gestational-age (SGA) as defined by the Delphi consensus protocol. This study aimed to examine the atrial chambers using speckle tracking analysis to identify any changes that may be specific for either growth disturbance. Methods - Sixty-three fetuses were evaluated with an estimated fetal weight <10th percentile who were classified as FGR or SGA based on the Delphi consensus protocol. The atrial cardiac cycle was defined as end-diastole, end-systole, and end-diastole, equivalent to ventricular end-systole, end-diastole, and end-systole. The atrial size, shape, and contractility were computed from 24 transverse segments and one length measurement identified from speckle tracking analysis of the endocardium at end-diastole and end-systole. The z-score for each atrial measurement was computed using the mean and standard deviation equations from a control group of 200 fetuses. The z-score values were compared between the control and FGR/SGA fetuses as well as between FGR and SGA fetuses using the Kruskal-Wallis test. A P-value of <.05 was considered significant. Results - Of the 63 fetuses with an estimated fetal weight (EFW) <10th percentile, 60% (38/63) were classified as FGR and 40% (25/63) as SGA. The following abnormal atrial measurements were unique to FGR fetuses: decreased end-diastolic left atrial (LA) area, decreased LA base and mid-chamber end-diastolic width, decreased LA base sphericity index, decreased right atrial (RA) mid-chamber sphericity index, decreased LA ejection volume, and decreased LA emptying volume. The following were unique to the SGA fetuses: Increased RA mid-chamber length, decreased LA fractional area change, decreased RA reservoir strain, decreased RA basal-apical length fractional shortening, and decreased LA base width transverse fractional shortening. The significant difference was an increased LA mid-chamber length in the SGA fetuses. Conclusions - Fetuses with an EFW <10th percentile who are classified as either SGA or FGR demonstrate unique abnormalities of atrial size, shape, and contractility, thus allowing the examiner to differentiate between FGR and SGA fetuses.