Out of Sight, But Still Should Be in Mind

To the Editor:

CASE has published many interesting case series and reports over the years. As a busy congenital echo lab team, we think CASE represents a great source for practical cases that can benefit similar teams of readers and sonographers. One specific article, “Mysterious Infantile Cyanosis: An Imaging Case Series,” by Sudeep Sunthankar et al.,¹ caught our attention, and we decided to write this Letter to the Editor to highlight this aspect. We would like to congratulate the authors for putting together very interesting cases. The article calls for the consideration of cor triatriatum dexter (CTD) diagnosis in hypoxic neonates with right-to-left atrial-level shunting. This is an important discussion as it brings to light the idea that sonographers and medical providers often overlook certain diagnoses due to low prevalence, which can have a significant impact on providing the appropriate patient care in a timely fashion.

The article demonstrates that CTD can be present in otherwise structurally normal hearts, as well as alongside other complex congenital heart defects—specifically right heart chambers hypoplasia. This notion is intriguing and somewhat counterintuitive, because we are often quick to recognize right heart hypoplasia itself as the mechanism for right-to-left atrial-level shunting. However, less common causes like CTD should be considered as an origin for both right heart hypoplasia and right-to-left atrial-level shunting in the hypoxic neonate, and it needs to be fully evaluated in this clinical presentation.

Sonographers often have a mental checklist of structures to evaluate when right-to-left atrial-level shunting is present. The most important item, especially in a neonate, is pulmonary venous drainage, as total anomalous pulmonary venous return is always associated with obligatory right-to-left atrial-level shunting and any delay in making this diagnosis can have a huge impact on the clinical course. We would like to emphasize the importance of detailed interrogation of the right atrial anatomical structures as well. Cor triatriatum dexter is not the first thing one thinks about here, but it should be added to that checklist. Detailed two-dimensional and color Doppler sweeps of the right atrium in apical and subcostal views, as well as spectral Doppler interrogation of any unusual finding, should be performed anytime a right-to-left atrial-level shunting or right heart hypoplasia is present in an infant.

Although medical management has come very far, it is not perfect. Critical thinking, full understanding of physiology, and carefully enhanced imaging should always be encouraged as they often lay the foundation for better clinical care. One way to achieve this is by publishing image-based case series, like the one we highlighted here, which will attract the attention of imagers from all levels.