Implications of In Situ Thrombosis and Distal Embolization during Superficial Femoral Artery Endoluminal Intervention

Background: Endoluminal therapy for superficial femoral artery (SFA) occlusive disease is commonplace, but the incidence and outcomes of in situ thrombosis (IST) and distal embolization (DE) have not been well defined. The aim of this study was to examine the impact of IST and DE on long-term outcomes of SFA interventions. Methods: A database of patients undergoing endovascular treatment of the SFA was queried. Patients who developed either IST treated by pharmacomechanical lytic therapy or DE were selected and compared to those without either event (control). Kaplan-Meier survival analyses were performed to assess time-dependent outcomes, with 2-year outcomes reported. Factor analyses were performed using a Cox proportional hazard model for time-dependent variables. Results: There were 818 limbs that underwent endovascular treatment for symptomatic SFA disease (59% for claudication and 41% rest pain and tissue loss). In the control group, 69% underwent angioplasty, 16% underwent primary stenting, and 15% underwent laser/directional atherectomy. In the IST group, these numbers were 41%, 28%, and 31%, respectively, while in the DE group they were 35%, 32%, and 33%, respectively. Overall the rates were 7.3% with 3.5% suffering IST (all treated with lytic therapy) and 3.8% suffering DE (68% treated percutaneously and the remainder treated by embolectomy). Females were more likely to experience either event. Compared to the control group, only one-third of the patients who suffered DE had primary angioplasty, whlle the remainder underwent primary stenting or laser/directional atherectomy. There was no difference in primary, assisted primary, or secondary patency rates between the control and DE groups. DE resulted in significantly lower limb salvage (87 +/- 2% vs. 68 +/- 8%, control vs. DE, p < 0.05) and freedom from recurrent symptoms (73 +/- 2% vs. 69 +/- 8%, control vs. DE, p < 0.05), while IST treated with lytic therapy was associated with lower patency (67 +/- 2% vs. 37 +/- 6% primary, 77 +/- 2% vs. 41 +/- 9% assisted primary, and 79 +/- 2% vs. 44 +/- 9%, secondary, control vs. IST, p < 0.01). There was no difference in outcomes based on whether surgical or percutaneous therapy was used to treat DE. While preoperative tibial runoff did not influence limb loss after DE, it was significantly associated with decreased patency after IST. Conclusion: DE during SFA interventions is associated with limb loss independently of preoperative runoff and subsequent intervention while the use pharmacomechanical lytic therapy for IST is associated with loss of patency but equivalent limb salvage and freedom from recurrent symptoms.