Why is this study important?

• The use of optical coherence tomography (OCT) for plaque characterization and preparation guidance has been advocated versus conventional methods to improve calcified lesions percutaneous coronary intervention (PCI) outcomes. However, this has never been evaluated in a prospective randomized controlled trial (RCT). The CALIPSO trial aimed to assess the technical outcome superiority of OCT over angiography alone for calcified lesions PCI guidance. 

What question was this study supposed to answer? 

• CALIPSO is a prospective multicenter trial that randomized patients with stable moderate-to-severe calcified coronary lesions between OCT vs angio-guided PCI groups. In the OCT arm, patients were treated according to a predefined algorithm based on the target lesion pre-PCI OCT analysis, whereas the strategy was left at the discretion of the operator in the angiographic-alone arm. All patients underwent a final OCT run analysis for primary endpoint assessment (minimal stent area/MSA) assessment. 

What did the study show?  

• A total n=134 patients were included in the final analysis (n=65 OCT group; n=69 angio group). The baseline characteristics of the groups were well balanced, but advanced plaque preparation was more frequently used in the OCT arm (63% vs. 37%, p=0.002). The final MSA was larger in the OCT than in the angiographic-alone group (6.5 (5.5-8.1) vs. 5.0 (4.1-6.1) mm2, p<0.001). Significantly better geometric stent expansion, higher average stent area, and shorter major malposition length were also observed in the OCT group compared to the others. There was no difference in peri-procedural complications incidence, neither in contrast medium volume or procedure duration between groups. 
• The use of Intravascular Lithotripsy (IVL) was almost four times higher in the OCT arm than in the angiographic-alone arm. Overall, IVL was used in about half of the OCT-guided group.
• Of note is that the anticipation of successful OCT catheter crossing was an inclusion criterion for this study. Hence, OCT catheter uncrossable lesions that needed rotational atherectomy upfront were not included in this study.

Key takeaway:

• The CALIPSO trial shows that OCT guidance resulted in better stent implantation technical results than angiographic-alone guidance in patients with calcified lesions PCI, without any safety concerns. However, whether this technical superiority in terms of imaging endpoints will translate into clinical benefit should be assessed in future studies.