Author + information
- Jiang Ming Fam1,
- Matthieu de Beule2,
- Nicolas van Mieghem3,
- Roberto Diletti1,
- Bert Everaert3 and
- Robert-Jan Van Geuns3
With improved percutaneous coronary intervention (PCI) techniques, PCI has emerged to be a safe option for revascularization with good long term outcomes in selected patients with unprotected left main coronary artery (uLMCA) lesions. Overexpansion beyond nominal size is a common procedure to ensure adequate stent apposition during left main stenting to improve clinical outcome. However there is limited data concerning the feasibility and safety of aggressive post dilation of metallic stent platforms during left main stenting to achieve apposition and reduce focal underexpansion.
The objectives of this study are to investigate if overexpansion can be achieved beyond the recommended stent expansion limit for a 4.0mm metallic stent and to compare different expansion techniques to achieve optimal apposition and study the effect of overexpansion on the mechanical performance of the stent.
We performed bench testing to measure the effect of overexpansion on the stent performance of thin strut (74μm) 4.0 mm drug eluting platinum chromium stents (DES) (Synergy IITM, Boston Scientific, Natwick, MA, USA) in silicon phantom models of 6 mm diameter. We tested the stents in the following 5 models; using a 6.0 mm balloon with Proximal Optimisation Technique (POT) at low (nominal) pressure of 6 atm (Group 1- POT-LP); and rated burst pressure (RBP) of 14 atm (Group 2- POT-RBP); Final Kissing Balloon Dilation (FKBD) methods using relatively undersized (‘US’) 3.5mm and 4.0mm balloons at RBP (Group 3 FKBD-US); FKBD using adequately sized 4.0mm and 5.0mm balloons at low pressure (Group 4- FKBD-LP) and finally at RBP (Group 5- FKBD- RBP).
The platinum chromium stents 4.0mm stent reached an outer diameter of only 5.1mm by using a 6.0 mm balloon at 6 atm. Further postdilatation with higher pressures (14 atm) resulted in a stent outer diameter of 6.0mm, demonstrating a safety margin above the designated expansion limit. Simultaneous kissing with undersized balloon diameters resulted in a high ellipticity index and importantly malapposition. Using correctly sized balloons, stent area improved but ellipticity remained and malapposition was less but still higher compared to POT-LP and POT-RBP.
Our study shows that the thin strut platinum chromium 4.0mm stents can be safely expanded with the use of POT beyond the overexpansion limit of 5.75mm with optimal stent apposition and performance. Proximal optimisation using adequately sized balloons and high pressure is advised to achieve optimal outcome in left main stenting.