Visualization of subclavian vein on Tc-99m MAA transarterial lung perfusion scintigraphy raises the possibility of macrovascular shunt in patients with AVM

Tc-99m MAA transarterial lung perfusion scintigraphy (TLSP) is known to be useful to evaluate the amount of shunt in patients with arteriovenous malformation (AVM) of extremities. We investigated the clinical significance of appearance of subclavian vein (SV) on upper extremity TLPS. 12 patients with upper extremity AVM were included in the study. Dynamic images of chest were obtained for 4 minutes and 5mCi Tc-99m MAA was injected i.v before imaging and intraarterially at ipsilateral distal brachial artery during imaging. On the pulmonary time activity curve, %shunt was calculated. AVM with %shunt more than 30% was considered to have macrovascular shunt. There were 8 right and 4 left AVM lesions (10 hand, 3 forearm and 2 upper arm lesions). The SV was observed on 5 of 12 dynamic TLPS. Calculated %shunt of 12 patients ranged from 2.0% to 99%. All 5 patients with visualization of SV had macrovascular shunt and repeated examinations in 2 patients showed identical results, which could exclude technical artifact. Meanwhile, only 2 of 7 patients without visualization of SV had macrovascular shunt. The sensitivity and specificity of visualization of SV for macrovascular shunt is 71.4% and 100%. Visualization of subclavian vein on Tc-99m MAA dynamic TLPS can help discriminate macrovascular from microvascular shunt in patients with upper extremity AVM