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Pulmonary artery/aorta ratio in simple screening for fetal outflow tract abnormalities during the second trimester
S F Wong1, C Ward, A Lee-Tannock
1Department of Maternal Fetal Medicine, Mater Mothers' Hospital, South Brisbane, QLD, Australia. shellwong@hotmail.com
Insights
The pulmonary artery/aorta (PA/AO) ratio, measured via ultrasound in the three-vessel view, can effectively screen for congenital heart outflow tract abnormalities in fetuses. This simple tool shows up to 86% sensitivity in detecting these serious conditions.
Area of Science:
- Fetal Medicine
- Pediatric Cardiology
- Medical Imaging
Background:
- Congenital heart disease (CHD) presents significant mortality and morbidity risks in newborns.
- Prenatal detection rates for congenital outflow tract anomalies via ultrasound remain suboptimal.
- Effective screening tools are crucial for early identification and management of fetal cardiac defects.
Purpose of the Study:
- To establish a normative nomogram for the pulmonary artery/aorta (PA/AO) ratio using the three-vessel view in fetal ultrasound.
- To evaluate the PA/AO ratio as a potential screening tool for congenital cardiac outflow tract abnormalities.
Main Methods:
- Prospective evaluation of 966 fetuses (16-24 weeks gestation) and 46 with known outflow tract abnormalities.
- Measurement of pulmonary artery (PA) and aorta (AO) diameters in the three-vessel view.
- Calculation of the PA/AO ratio, construction of a nomogram, and comparison with affected fetuses.
Main Results:
- The mean PA/AO ratio in normal fetuses was 1.16 (SD 0.18), with a 95% CI of 0.87-1.58.
- Fetuses with outflow tract abnormalities (n=43) showed a median PA/AO ratio outside the 95% CI in 86% of cases.
- The study identified specific ranges for PA and AO diameters within the evaluated gestational period.
Conclusions:
- The PA/AO ratio measured in the three-vessel view serves as a valuable initial screening tool for fetal outflow tract anomalies.
- This method demonstrates a potential sensitivity of up to 86% for detecting these cardiac defects.
- The PA/AO ratio offers a simple, effective approach to improve prenatal screening for congenital heart abnormalities.
Objectives:
Congenital heart disease is associated with high mortality and morbidity rates, being the most life-threatening defect in the first month of postnatal life and accounting for approximately half of all childhood mortality from birth defects. Despite this, the prenatal detection rate for congenital outflow tract anomalies by ultrasound imaging is relatively low. The aim of this study was to establish a nomogram for the pulmonary artery/aorta (PA/AO) ratio measured in the three-vessel view plane. This ratio was investigated as a simple screening tool for congenital cardiac outflow tract abnormalities.
Methods:
The study was a prospective evaluation of 966 singleton fetuses at 16-24 weeks of gestation and 46 fetuses with congenital cardiac outflow tract abnormalities. The diameters of the pulmonary artery and aorta were measured in the three-vessel view. The PA/AO ratio was calculated and a nomogram was constructed. The mean and 95% CI for the ratio were defined and the PA/AO ratios of cases with outflow tract abnormalities were plotted against the values for normal fetuses.
Results:
The gestational age of the normal group ranged from 16 to 24 weeks, with a median of 19 weeks. The pulmonary artery diameter measured between 2.1 and 4.93 mm (mean, 3.3 mm) and the aorta measured between 2.1 and 5.2 mm (mean, 2.93 mm). The mean (SD) PA/AO ratio was 1.16 (0.18) (95% CI, 0.87-1.58; range 0.61-1.86; median, 1.14). For fetuses with outflow tract abnormalities, the median gestation was 19 weeks and 37/43 (86%) had a PA/AO ratio outside the 95% CI.
Conclusions:
The PA/AO ratio derived from measurements in the three-vessel view plane can be used as an initial screening tool for outflow tract anomalies and may have a sensitivity of up to 86%, with a 5% false-positive rate.
