The angiographic evaluation of left main (LM) disease can present challenges and requires additional intravascular imaging in order to make the correct decision regarding revascularization. The angle of the ostium often presents challenges for the accurate angiographic evaluation of disease. FFR evaluation of the LM depends not only on the lesion characteristics but also on the territory supplied by the vessel. FFR is very reliable in the presence of isolated LM disease. It seems to be accepted that an FFR in the LM <0.8 or an MLA <5.9-6.5 mm2 is the threshold for revascularization. FFR is a potential tool for assessing the hemodynamic significance of an LM stenosis. A poor correlation has been noted between quantitative coronary angiography and FFR, which points to the shortcomings of relying on angiography alone in evaluating LM lesions. Angiographically intermediate LM lesions with an FFR of ≥0.80 can have revascularization deferred with favorable long-term outcomes.

OCT provides precision information very quickly and helps in the treatment of cardiovascular disease, including LMCA disease. OCT can help assess atherosclerotic plaque and visualize thrombus. It can also assist in evaluation of the lumen area with accurate automated measurements. During PCI, it can help in stent placement and may be used to assess stent apposition and tissue coverage and assist in the identification and quantification of stent coverage. OCT is indicated for the assessment of lesions and for guidance of stent sizing and implantation. OCT can help assess the thickness of calcium plaques which may affect the lesion preparation strategy. Dissections resulting from predilatation are also detected by OCT that can be taken into account when assessing the required stent length.

There is a benefit to integrating FFR and OCT technologies for the evaluation of disease and PCI optimization. They enable physicians to identify, diagnose and treat CAD while improving outcomes. FFR provides an accurate assessment of the functional significance of a lesion in varied clinical scenarios, such as single lesions, diffuse disease, left main, ostial disease, side branches. OCT further helps in the assessment and treatment of disease through high resolution lesion evaluation, both pre- and post-intervention.