[Management of stent under-expansion].

Stent under-expansion represents a negative prognostic factor, because of the risk to develop intrastent restenosis and stent thrombosis. It is often due to excessive calcium burden at the target lesion level. The list of devices available for the treatment of stent under-expansion includes super high-pressure non-compliant (NC) balloons, excimer laser and intravascular lithotripsy.NC OPNTM balloons (SIS Medical AG, Winterthur, Switzerland) reach much higher pressures than those of standard NC balloons (up to 35 atm), so they are able to overcome the resistance given by the calcific plaque. The excimer laser catheter instead generates ultraviolet light pulses with low penetration power. This one fragments the atherosclerotic material surrounding the implanted stent. This technology has proven to be extremely effective, however it requires specific operator experience to reduce the risk of serious complications. Intravascular lithotripsy is the most recent method, and it has shown very promising results so far. The Shockwave Medical device (S-IVL; Shockwave Medical Inc, Santa Clara, CA, USA) emits sound waves that act selectively on the calcific component, breaking it up and making the vessel more compliant.