EP09.07: Impact of sample volume position in calculating fetal cardiac output

Fetal cardiac output is known to assess fetal cardiac function, which is calculated using the cross-sectional area of the aortic valve and pulmonary valve and velocity time integral (VTI) with pulse Doppler. Although VTI is changed by the position of sample volume, on or distal to the valve, the impact to the cardiac output is unknown. Thirty-four patients were enrolled as normal fetal heart in fetal cardiology outpatients in our hospital. In recording VTI of the aortic and pulmonary valve, sample volume was positioned on the valve (valve group; V) and distal to the valve (supra-valve group; S). Cardiac output calculated by each VTI were compared. Additionally, electronic spatiotemporal image correlation (eSTIC) volume data was obtained from 17 patients and left ventricle cardiac output was calculated (eSTIC group). Correlation of left ventricle output calculated among eSTIC, V, and S groups was assessed. Aortic VTI was 8.5 ± 2.2cm vs 9.3 ± 2.5cm (Group V vs S, p < 0.01), and pulmonary VTI was 7.0 ± 1.7cm vs 8.2 ± 2.1cm (p < 0.01), suggesting that group S had significantly higher VTI. Combined output was 384 ± 125 vs 439 ± 140mL/kg/min, revealing that group S had significantly high cardiac output. Cardiac output of left ventricle was as follows; eSTIC group; 133 ± 69mL/kg/min, V group; 140 ± 73mL/kg/min, S group; 157 ± 77mL/kg/min. Correlation coefficient was 0.928, bias was -7.3 ± 27.4, and LOA was -61–46.4 between the eSTIC and V groups. Correlation coefficient was 0.917, bias was -24 ± 31, and LOA was -95–-37 between the eSTIC and S groups, showing that V group showed more similar results to eSTIC group. The position of sample volume has significant difference to cardiac output. Cardiac output measured by sample volume on the valve may be more accurate.