Various studies have confirmed that FFR and IVUS-guided PCI provide superior clinical outcomes compared to angiographic-guided PCI. The use of FFR to guide PCI decisions has been shown to decrease the frequency of urgent revascularizations in patients treated with drug-eluting stents compared to medical therapy alone.4) IVUS plays a significant role in enhancing stent implantation, which has been linked to reduced mortality and fewer instances of target-vessel revascularization.5) The proposed mechanism by which intracoronary imaging leads to improved outcomes involves providing precise vessel size measurements, enabling better stent expansion and contact with the vessel wall, as well as identifying potential complications like dissections; this contributes to a reduced risk of lesion recurrence or restenosis.6) Moreover, a study reported that IVUS has shown that more than one-third of patients (39%) fail to meet IVUS optimization criteria even when angiographic criteria are met, leading to poorer clinical outcomes.7) Therefore, the discrepancy between angiographic assessment by QCA-derived diameter stenosis and assessments using FFR or IVUS in intermediate coronary lesions can become a significant topic of discussion.

In this issue of the Journal, Lee and colleagues8) report the discrepancies between QCA and FFR or IVUS in evaluating intermediate coronary lesions. The post hoc analysis of FLAVOUR trial reveals that approximately 28.2% of intermediate lesions show discordance between QCA and FFR, while 32.4% show discordance between QCA and IVUS. These findings emphasize the necessity of advanced assessments to enhance diagnostic precision and patient outcomes, not based on QCA only. Importantly, the present study showed that 2-year clinical outcomes indicate that FFR- or IVUS-guided strategies yield comparable results in managing discordant lesions. For instance, lesions significant by QCA but negative by FFR or IVUS saw deferred PCI without compromising patient outcomes, advocating for a conservative approach in such scenarios. The authors have defined this situation as a mismatch.

In cases of mismatch, the FFR negative group showed a primary endpoint rate of 5.9% at 2 years, while the IVUS negative group showed a lower rate of 3.4%; though not statistically significant, this indicates a trend toward better outcomes with IVUS. The recent PREVENT study compared optimal medical treatment alone versus preemptive stenting with optimal medical treatment in lesions found negative by FFR, reporting a risk reduction of 31% with rates of 5.2% and 3.0%, respectively.9) This suggests the inherent limitation of FFR in not being able to reveal lesion characteristics. In context, the present study showed that both the mismatch group and the reverse mismatch group had numerically lower event incidences in the IVUS groups compared to the FFR groups, indicating the need for further research to explore the correlation between plaque vulnerability and subsequent acute coronary events.10)

Despite these considerations, the present study can provide a useful option for institutions unable to perform both FFR and IVUS. By implementing either FFR or IVUS, the potential discordance arising from decisions based solely on QCA can be mitigated, ultimately expected to improve patient clinical outcomes.