Medical Student Monash University Monash University Melbourne, Victoria, Australia
Background: Transposition of great arteries (TGA) is a common cyanotic heart defect. BAS aims to improve both circulatory mixing and oxygenation. Previous studies have combined infants with an intact ventricular septum (IVS) and those with a ventricular septal defect (VSD). Additionally, the septostomy was performed much later after birth in those studies.
Objective: The objectives were to ascertain improvement in oxygenation parameters after BAS and to assess for any correlation between the ASD size and oxygenation variables.
Design/Methods: A retrospective audit for data over ten years (2010-2020) was performed for infants with D-TGA with IVS who had undergone BAS. Oxygenation data for equal time duration either side of the procedure was compared. In the Unit, prostaglandin infusion (PGE1) is started based on pre-ductal saturations (<75%) and/or restrictive inter-atrial shunting. A single cardiologist masked to the clinical data measured the ASD diameter in 2-Dimensional mode. Data are presented as mean +/- standard deviation or median (interquartile range [IQR]). Student’s t-test was used for the comparison of pre-post procedure variables. Pearson coefficient was used to determine correlation between ASD size and oxygenation.
Results: Our study on 25 infants with TGA and IVS noted that the procedure was performed at a median (interquartile range) of 3 (2, 4) hours after birth. PGE1 was administered to the majority of infants (20/25 [80%]). Other relevant cohort characteristics are described in Table 1. BAS procedure resulted in a significant increase in paO2 (24±5 to 40±6mm Hg, p<0.001) and pre-ductal oxygen saturations (67±18 to 81±11%, p=0.003) (table 2). This was accompanied by a significant increase in ASD size (1.8 +/- 0.6 to 4.8 +/- 0.7 mm, p<0.001). However, no correlation was noted between ASD size and oxygenation variables (table 3). Conclusion(s): In our study on infants with TGA and IVS managed with BAS, while the procedure led to a significant increase in oxygenation variables, ASD size did not correlate with oxygenation. Pulmonary vascular resistance may be an additional important physiological variable determining oxygenation.