Objectives: To examine the effect of the Symbiot PTFE-covered stent on distal embolization during percutaneous coronary intervention (PCI) in saphenous vein grafts (SVGs).
Background: Covered stents are intended to trap friable debris and reduce distal embolization during vein graft PCI, but have consistently failed to improve clinical outcomes in randomized trials. The reasons for this lack of benefit are unclear.
Methods: Thirty patients undergoing SVG PCI, and eligible for a FilterWire distal protection device, were randomized to Symbiot or to a conventional bare-metal stent. Postprocedure, the FilterWire was removed, fixed in formalin, and photographed under high magnification. The primary end-point was embolic debris area, measured by semi-automated edge-detection analysis of digital images. Secondary end points were no-reflow, "Filter no-reflow", and distal embolization.
Results: There was no significant difference between the Symbiot and conventional stent groups in embolic debris area (10.5 +/- 7.2 versus 6.6 +/- 7.8 mm2; p = 0.18). No-reflow occurred in 3/14 Symbiot versus 0/16 conventional (p = 0.09), and final TIMI flow was lower in the Symbiot group (2.7 +/- 0.5 versus 3.0 +/- 0.5; p = 0.01). However, there was no difference in the incidence of Filter no-reflow (7/14 versus 7/16; p = NS) or distal embolization (9/14 versus 8/16; p = NS). Distal embolization in the Symbiot group occurred predominantly after postdilatation (7/9; p = 0.05).
Conclusions: The Symbiot PTFE-covered self-expanding stent does not reduce distal embolization compared to a conventional bare metal stent. Distal embolization with the Symbiot occurs almost exclusively after mandatory postdilatation. These findings may explain the failure of the Symbiot, and of covered stents in general, to improve clinical outcomes during vein graft PCI.