TAC: A Review of Prenatal Diagnosis, Associated Findings, and Postnatal Outcome of Fetuses

Truncus arteriosus communis (TAC) is a rare conotruncal birth defect of the heart. Truncus arteriosus occurs in less than one out of every 10,000 live births. There are about 250 cases of truncus arteriosus in the United States every year. It is most commonly found in offspring borne of a diabetic mother. It occurs when the blood vessel coming out of the heart in the developing baby fails to separate during development, leaving a connection between the aorta and pulmonary artery. 

A study was conducted to assess the range of cardiac and chromosomal anomalies, the intrauterine course, and the postnatal outcome of fetuses with TAC from two tertiary centers. While collecting data, TAC was distinguished into three different categories based on Collets and Edward’s, and Van Praagh’s based on existing arteries, arising MPA and aorta arch anomalies.  All the cases were differentiated according to five pregnancy outcomes i.e., Termination of pregnancy, intrauterine fetal, neonatal death, death in infancy or childhood, and survivors. The sources used for data collection were medical files, stored ultrasound images, and recordings. Also, factors such as maternal age, gestational age at first diagnosis type of TAC, etc. were considered.

Of all the data collected 39 cases of TAC were diagnosed prenatally. The mean gestational age at the first diagnosis was recorded as 22 weeks with 2 cases losing follow-up. 87.5% of TAC cases were diagnosed correctly with an accuracy of 90.5% in subtype identification. It was also visualized that in 38.5% of cases the fetuses had additional chromosomal anomalies over the 26.5% cases where TAC was an isolated finding. Microdeletion in chromosome 22q11.2 was seen as the most prevalent cause in 17.6% of subjects whereas extra-cardiac and cardiac associated with chromosomal anomalies were found in between 8.8% and 58.8%.  

The outcome was recorded as 14 terminations, 1 intrauterine fetal death, 5 postnatal death, and 14 infants alive at the last follow-up. The survival rate was 42 months on average. For survivors, postoperative health was found stable in 78.6% but 21.4% were significantly impaired due to non-cardiac problems. It can be concluded that TAC is a complex cardiac anomaly that can be diagnosed with high precision in prenatal stages. TAC is most often correlated to chromosomal and extra-cardiac anomalies leading to terminations and before operative mortality. Also, the postoperative health status in infants showed positive values irrespective of the subtype of TAC.

Source: Abel J.S, et al., Arch GynecolObstet 304, 1455-1466 (2021)