Impact of Vascular Geometry on Thrombosis in Pediatric Patients With Modified Blalock‐Taussig‐Thomas Shunt: A Pilot Study

Background Thrombosis in modified Blalock‐Taussig‐Thomas shunts (mBTTS) poses a life‐threatening risk for infants with shunt‐dependent congenital heart disease. Although hemodynamics influence thrombosis, the specific geometric contributors remain unclear. This study aimed to identify key variables to inform future hemodynamic analysis, hypothesizing that brachiocephalic, subclavian artery, mBTTS, and/or pulmonary artery (PA) geometry play a critical role in clot formation. Methods and Results We retrospectively analyzed 11 infants with hypoplastic left heart syndrome who underwent mBTTS placement. Using computed tomography and magnetic resonance imaging, we generated 3‐dimensional models of the shunt and surrounding vasculature. Geometric variables related to shunt positioning and vascular insertion were measured and compared between patients with (n=5) and without (n=6) thrombotic occlusions. Significant differences in vascular geometry were observed between occluded and nonoccluded shunts. Occluded shunts had longer PA lengths (12.4 mm versus 8.4 mm, P =0.0130), increased variance in PA radius (0.03 versus 0.008, P =0.0216), greater PA tortuosity (1.03 versus 1.01, P =0.0043), and increased variance in torsion across the brachiocephalic and subclavian arteries (3200 mm −1 versus 17 500 mm −1 , P =0.0390). These findings support our hypothesis that the vascular geometry surrounding the mBTTS plays a critical factor in clot formation. Additional variations in PA, brachiocephalic and subclavian artery geometry approached significance. Conclusions Significant geometric differences in the PA, brachiocephalic, and subclavian arteries were associated with mBTTS thrombosis, supporting the hypothesis that vascular geometry plays a critical role in clot formation. These findings provide a foundation for future hemodynamic analyses and may inform surgical planning to reduce thrombosis risk in patients with mBTTSs.