P734Feasibility of strain and strain-rate analysis of the fetal heart in an experimental rodent model

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Aim: Fetal heart is challenging because of its small size, high heart rate, restricted physical access to the fetus and impossibility of ECG recording. We aimed to assess feasibility and reproducibility for strain and strain-rate (SR) measurements by tissue Doppler imaging (TDI) and 2Dstrain in a pregnant rabbit model.Methods: Ultrasound was performed in 30 fetuses placing the probe directly on the uterine wall at 30 days of gestation. 2D and color TDI in apical four chamber views were recorded for subsequent analysis. Caution was taken to achieve >250 fps. For each acquisition, 15s of non compressed data were stored in cine-loop format and analyzed offline. Aortic valve closure was marked from aortic flow and the onset of each cardiac cycle was manually indicated in the 2D images. Sample volume and area length were standardized at the minimum size. Two observers measured peak systolic left ventricular strain and SR.Results: Strain and SR measurements were feasible in 93% of the acquisitions. Mean time spent for 2Dstrain analysis was 8 min with an intraclass agreement coefficient of 0.88(95%CI 0.75-0.94) and 0.89(95%CI 0.79-0.95) for peak systolic strain and SR respectively. Agreement between observers using 2Dstrain showed a mean difference of 0 with 95% limits of agreement -8.2 to +8.2 for strain and 0(-1.2 to 1.1) for SR. Mean time spent for analyzing TDI images was 14 min with an ICC of 0.63(95%CI 0.39-0.80) and 0.61(95%CI 0.35-0.80) for peak systolic strain and SR respectively. Agreement between observers using TDI showed a mean difference of 3.5(-15 to 22) for strain and 0.1(-5.7 to 5.8) for SR.Conclusions: Evaluation of left ventricular strain and SR of the fetal heart is feasible by 2Dstrain or TDI and has a reproducibility similar to previous data in humans.

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