Ultrastructural Study of Platelet Behavior and Interrelationship in Sprouting and Intussusceptive Angiogenesis during Arterial Intimal Thickening Formation

Platelets in atherosclerosis, bypass stenosis, and restenosis have been extensively assessed. However, a sequential ultrastructural study of platelets in angiogenesis during the early phases of these lesions has received less attention. Our objective was the study of platelets in angiogenesis and vessel regression during intimal thickening (IT) formation, a precursor process of these occlusive vascular diseases. For this purpose, we used an experimental model of rat occluded arteries and procedures for ultrastructural observation. The results show (a) the absence of platelet adhesion in the de-endothelialized occluded arterial segment isolated from the circulation, (b) that intraarterial myriad platelets contributed from neovessels originated by sprouting angiogenesis from the periarterial microvasculature, (c) the association of platelets with blood components (fibrin, neutrophils, macrophages, and eosinophils) and non-polarized endothelial cells (ECs) forming aggregates (spheroids) in the arterial lumen, (d) the establishment of peg-and-socket junctions between platelets and polarized Ecs during intussusceptive angiogenesis originated from the EC aggregates, with the initial formation of IT, and (e) the aggregation of platelets in regressing neovessels (‘transitory paracrine organoid’) and IT increases. In conclusion, in sprouting and intussusceptive angiogenesis and vessel regression during IT formation, we contribute sequential ultrastructural findings on platelet behavior and relationships, which can be the basis for further studies using other procedures.

Percutaneous glue embolization of arteriovenous fistula of in situ saphenous vein bypass graft: Case report and literature review

Objectives Arteriovenous fistulas (AVFs) of an in situ saphenous vein bypass can be managed surgically or through endovascular coil embolization. The complications associated with the surgical wounds required for side branch ligature can be minimized through selective vein ligature and interrupted small incisions, but endovascular methods are time-consuming and limited by vein size. In this case report, we describe percutaneous ultrasound (US)-guided balloon-assisted direct glue injection as an alternative treatment strategy for AVF closure. Methods We treated a patient with a delayed AVF in a femoral-popliteal in situ saphenous vein bypass. The patient came to our attention for the recurrence of chronic limb-threatening ischemia (CTLI) 4 years after the initial bypass creation. Ultrasound and computed tomography angiography (CTA) showed a double tandem graft in significant stenosis below an AVF connected with the deep venous system. Treatment included percutaneous angioplasty of the bypass stenosis and contemporary AVF closure via ultrasound-guided glue injection. Results We successfully performed endovascular angioplasty with a drug-eluting balloon of the bypass stenosis and ultrasound-guided fistula embolization with cyanoacrylate Glubran 2. Angiography after the procedure showed bypass graft patency, no residual stenosis, and complete closure of the AVF. Results were confirmed with US. Conclusions Percutaneous embolization using glue could be a useful technique for AVF closure. It is a minimally invasive method that reduces the need for skin incisions during in situ saphenous grafting or endovascular revascularization.