Strut apposition after coronary stent implantation visualised with optical coherence tomography

Aims: To describe different patterns of stent strut apposition, as visualised with optical coherence tomography. Methods and results: Strut thicknesses were reconstructed according to the manufacturers' specifications. The stent area (SA) was measured by connecting the reconstructed abluminal surfaces of struts with a trace line, and the vessel wall area (VWA) was estimated from the abluminal strut surfaces, as well as from the lumen border, in cases of struts that were separated from the vessel wall by flush. Strut apposition was evaluated by comparing the SA- and VWA traces. We observed four patterns of strut apposition. Based on these, stent struts could be classified as: (I) apposed struts, (II) struts overlying the ostium of a side branch, (Ill) malapposed struts that were clearly separated from the vessel wall by flush, and (IV) pseudoapposed struts that were not separated from the vessel wall by visual estimate, but were malapposed in the sense that SA<VWA. Pseudoapposed struts were found in frames with "flower-shaped" lumen contours, and were often surrounded by structures of a lower signal intensity than the rest of the vessel wall. Conclusions: For a detailed analysis of strut apposition with OCT, we reconstructed strut thicknesses and estimated stent- and vessel wall areas. With this method, we found four types of strut apposition, where pseudoapposed struts constitute a type of struts not previously described. The clinical importance of pseudoapposed struts remains to be settled.