Background: Congenital heart diseases are the most common type of congenital malformations. Some of them may pass
unnoticeable in the first days or maybe years of life, but the others are pretty serious and life-threatening due to major
malformations that lead to the mixing of oxygenated and deoxygenated blood. Most of these cases are not repairable and
require separating the venous and arterial blood to help improve oxygen saturation (SpO2
).
Aim: The study aims to evaluate the mid and long-term effects of left modified blalock-taussig (MBT) shunt after
bidirectional cavopulmonary shunt.
Patients and Methods: A retrospective cohort study was conducted on 20 patients who underwent MBTS after
Bidirectional Glenn. We evaluated the mid and long-term effects of MBTS in those patients, especially SpO2
 and
echocardiographic findings. The study considered the ethical principles of the Helsinki Declaration approval from the
research ethics committee at our institution (MS 510/2023).
Results: There was a significant increase in postoperative SpO2
 in comparison to preoperative SpO2
 (P<0.001) with a
mean difference of 20.95%.
Conclusion: Congenital cyanotic heart disease represents a life-threatening condition where the main problem is
desaturation due to the mixing of arterial and venous blood. Bidirectional Glenn is a step to separate the oxygenated and
deoxygenated blood. But later on, SpO2  continues to decline and further intervention is needed. In this study, we found
that MBTS provides a postoperative significant increase in SpO2  in a wide group of those patients even who are not
candidates for other operations without significant complications.