Defining optimal stent overexpansion strategies for left main stenting : insights from bench testing

Aims: Left main stenting frequently requires overexpansion of stents which can be performed by proximal optimisation technique (POT) or final kissing balloon dilation (FKBD). Yet, there are limited data concerning the effect of post-dilation of metallic stents beyond the overexpansion limit. The objectives of this study were to evaluate stent performance after overexpansion using POT or FKBD. Methods and results: We deployed 4.00 mm drug-eluting platinum-chromium stents in silicone models of 6.00 mm diameter. We compared stent expansion and apposition using: 1) POT with 6.00 mm balloons using low, standard and high pressures (LP, SP and HP, respectively), and 2) final kissing balloon dilation (FKBD) using undersized (US) balloons at SP and optimally sized (OS) balloons at LP and SP. The platinum-chromium 4.00 mm stent can be expanded to an outer diameter of 5.10 mm by POT using a 6.00 mm balloon at LP. Further post-dilatation at higher pressures (SP, HP) resulted in an outer diameter of 6.00 mm. FKBD with US balloons resulted in a high ellipticity index and malapposition; with OS balloons, stent area improved but ellipticity and malapposition were still higher compared to POT. After overexpansion, the radial strength of metallic stents was maintained. Conclusions: In PCI involving relatively larger vessel diameters such as left main stenting, POT but not FKBD can safely expand the platinum-chromium 4.00 mm stent beyond the overexpansion limit to 6.00 mm with optimal stent apposition and performance. POT may be the technique of first choice to achieve optimal stent expansion in left main stenting but requires higher pressures.