Lighting Up the Dark: Indocyanine Green Angiography for Assessing Free Flap Autonomization After Late Arteriovenous Loop Thrombosis.

Background: Although delayed clinically apparent free flap compromise from late vascular thrombosis is uncommon, it continues to pose significant diagnostic and therapeutic challenges. This retrospective case series assesses cases of late thrombosis after arteriovenous loop and free flap reconstruction. Methods: Medical records, including demographics, surgical details, vascular status, flap perfusion imaging, treatment, and outcomes of patients from hospital records who underwent arteriovenous loop and free flap reconstruction between 2003 and 2025, were extracted and analyzed. Results: A total of 3 out of 123 cases (2.4%) developed clinically apparent perfusion problems in the transferred tissue of the lower extremity between the 30th and 86th postoperative days. Digital subtraction angiography confirmed arterial thrombosis in all 3 cases, whereas indocyanine green angiography (ICG-A) demonstrated a centripetal skin perfusion pattern indicating autonomy of all included flaps. All patients were treated with therapeutic anticoagulation and strict bed rest with limb elevation. During the inpatient stay, stabilization of flap perfusion was confirmed by regular flap monitoring. Conclusions: This study highlights the value of ICG-A not only in detecting vascular occlusion but also in assessing flap autonomization, thereby guiding therapeutic decision-making in cases of late thrombosis. The "wait-and-see" triple treatment, consisting of repeated ICG-A, therapeutic anticoagulation, and strict bed rest with limb elevation, seems to have been an effective strategy in these 3 cases. However, demonstrable flap autonomy is essential before applying this approach.