Intravascular optical coherence tomography (OCT) can add value to angiography as a diagnostic as well as an intervention tool for PCI guidance. In diagnostic terms, it is important to separate two very distinct populations: Stable coronary artery disease (CAD) and acute coronary syndromes (ACS). For both populations, the key questions include the following - Is intervention required? If so, which vessel/lesion? With regard to procedure planning, intravascular OCT can help with planning every coronary intervention procedure.

When it comes to lesion preparation, we need to ascertain if there is a need for atherectomy, if there is a need for thrombectomy, if predilatation is chosen over direct stenting, how aggressive should the procedure be, etc. In terms of stent selection, what length and diameter are appropriate, is there a need for multiple stents or a single stent, if a need exists for overlapping stents, where is the best location, etc., need to be determined.

Other potentially significant findings revealed by intravascular OCT after stent implantation are stent malapposition, edge dissections, and tissue prolapse.

The higher resolution and contrast between lumen and vessel wall obtained with intravascular OCT allow for a more detailed lumen segmentation compared with IVUS, which is marked in irregular calcified plaque segments. Reference vessel lumen analyses as well as perfect circular phantom models show excellent agreement between intravascular OCT and IVUS, with lower interobserver variability obtained with intravascular OCT. OCT has unique features that favor its utilization in the setting of ACS. Intravascular OCT has 100% sensitivity (vs. 33% sensitivity of IVUS) in detecting intraluminal thrombus when compared with coronary angiography. OCT is suitable for the detection of non-CAD-related ACS causes like spontaneous coronary artery dissection. OCT-derived information could defer unnecessary stenting.

Calcium is the most important predictor of suboptimal stent expansion. OCT has high tissue penetration on calcium thus allowing for the assessment of calcium thickness. In terms of stent selection, the very fast pullback acquisition obtained with intravascular OCT makes the method a precise one for length measurements. The high-resolution nature of intravascular OCT unravels stent malapposition frequently.