Abstract Body (Do not enter title and authors here): Background: Prior reports demonstrate that the ductus arteriosus (DA) can become more curved as pregnancy progresses. This study investigates the question whether the degree of DA tortuosity is associated with changes in Doppler flow in the DA or right ventricular (RV) functional findings in fetuses with tortuous DAs but otherwise normal intracardiac anatomy. We hypothesize that greater tortuosity will be associated with higher DA flow velocity and negative impacts on RV function.

Methods: Fetuses diagnosed with tortuous DA from 01/2016 to 10/2023 and with gestational age of ≥ 32 weeks were evaluated. The degree of DA tortuosity was assessed as the minimum (sharpest) ductal angle in degrees, number of ductal bends, and ductal tortuosity grade (Table 1). Tortuosity grade was assigned as mild when a single bend in the DA had an angle > 90 degrees, moderate when a single bend in the DA had an angle < 90 degrees, and severe when there were ≥2 bends in the DA. DA flow was assessed as peak systolic flow velocity (PSV) and pulsatility index (PI) (Figure 1). Markers of RV function included degree of tricuspid regurgitation, RV size, ratio of RV to left ventricle (LV) size (RV/LV), RV function, RV hypertrophy and venous Dopplers. The association between DA tortuosity and both DA doppler flow and RV functional measures were assessed using linear regression. P-values of <0.05 were considered statistically significant.

Results: A total of 76 fetuses with a tortuous DA were evaluated; the average gestational age was 34.9 ± 1.7 weeks (range, 32.0 to 38.7 weeks). The clinical characteristics of the cohort were described in Table 1. Despite a wide variation in the degree of DA angulation, DA tortuosity was not associated with either DA PSV or PI. PSV was elevated in 32 of 76 (42.1%) subjects. A higher peak systolic ductal velocity was modestly correlated to a higher RV/LV ratio (r=0.24, p=0.04). Otherwise, neither DA tortuosity nor PSV correlated to any other measures of RV functional status.

Conclusions: Although significant, variable tortuosity of the DA can be seen in late gestation fetuses with otherwise normal cardiac anatomy. The degree of tortuosity was not associated with elevations in DA Doppler flow or significant changes in RV functional parameters. Elevated PSV in the DA – not predicted by DA tortuosity – was correlated only to increases in relative RV/LV size, without changes in other RV functional findings.