Evaluating fetal tricuspid and mitral annular plane systolic excursion (TAPSE and MAPSE) using spatiotemporal image correlation (STIC) M-mode

Objectives: 2D ultrasound TAPSE and MAPSE examination may characterise ventricular function in the fetus. We aimed to evaluate feasibility of STIC M-mode for measuring TAPSE and MAPSE in the second half of gestation. Methods: We recruited gravidae presenting from 20 to 34 weeks for routine surveillance, with structurally normal singleton pregnancies. STIC volumes of a complete cardiac cycle were acquired and saved. Manipulation of the volumes and measurements were performed offline in post-processing and in a lower speed. All unnamed volumes were evaluated by two operators to assess repeatability. 15 STIC volumes were also duplicated and appeared randomly three times each for intraobserver repeatability evaluation. The operators scrolled through each volume to optimise the 4 chamber view then rotated the cardiac apex to 12 o’clock. The M-mode beam was a ligned through the lateral aspect of the tricuspid valve annulus, parallel to the interventricular septum. The x and y axes were further adjusted in order to define the most appropriate distinct line to measure the maximum annular movement. The excursion, or vertical movement, of the tricuspid annulus during systole and diastole was measured from the M-mode wave amplitude. This process was then repeated for mitral annulus excursion. Inter- and intraobserver variability were tested with intraclass correlation coefficients (ICC). Results: 60 volumes from 16 gravidae were evaluated by eachoperator. The mean TAPSE was 5.4 (SD, 1)mm and 5.3 (SD, 1.1)mm measured by operator 1 and 2 respectively. The mean MAPSE was 4.3 (SD, 0.8)mm and 4.2 (SD, 0.7)mm measured by operator 1 and 2 respectively. ICCs for TAPSE were high with intraobserver ICCs of 0.94 and 0.92 for operator 1 and 2 and an interobserver ICC of 0.91. MAPSE ICCs were lower with intraobserver ICCs of 0.80 for both operators and interobserver ICC of 0.76. Conclusions: STIC allows easy and accessible evaluation of systolic function in the fetus, that is reliable and repeatable, more so for TAPSE than MAPSE