Accurate assessment of left main coronary artery (LMCA) disease is a challenging but critical task. Revascularization of hemodynamically significant left main disease has a clear mortality benefit, reduces risk of myocardial infarction, and improves quality of life. , However, both coronary artery bypass surgery and percutaneous coronary intervention of the LMCA carry significant risks.
Historically, cardiologists have relied on angiography to identify significant LMCA disease. However, multiple studies have shown poor correlation between angiographic percent diameter stenosis (DS%) and hemodynamic significance as assessed by fractional flow reserve (FFR), instantaneous wave-free ratio (iFR), and intravascular ultrasound (IVUS). , The LMCA has one of the highest rates of angiographic visual: functional mismatch at 40%, making angiographic assessment of significance largely a flip of the coin. A growing body of evidence has shown that FFR, iFR, and IVUS guided revascularization is superior to angiography alone. ,,
Further adding to this complexity is the fact that FFR, iFR, and IVUS can be discordant in a sizeable percentage of cases. In the iLITRO-EPIC07 study, iFR and FFR were discordant in 20% of cases. IVUS was used to further evaluate these patients, and was found to be discordant with FFR in 8.7% of cases and iFR in 14.6% of cases. Why these modalities may be discordant remains an ongoing area of investigation. Lesion anatomy (length, presence of tandem lesions, eccentricity, calcification, etc.) and volume of subtended myocardial tissue are likely contributing factors. In the iLITRO study, patients with discordant FFR and iFR values were revascularized if IVUS showed minimal luminal area (MLA) of less than 6 mm 2. In other words, IVUS was used as a third marker in case of discordance. Outcomes for MACE were noninferior in the group with deferred revascularization, and FFR appeared to correlate more closely with IVUS.
Demirtakan et al in a recent issue of American Journal of Cardiology used FFR, iFR, and IVUS in 34 patients who had angiographically intermediate LMCA disease. Their work again confirms that angiography correlates poorly with both hemodynamic assessment and IVUS (only 47% of lesions were significant by IVUS, 59% by FFR, and 38% by iFR). In 12/34 cases (35% of cases) at least one modality was discordant. FFR had higher rates of correlation with IVUS, successfully identifying all lesions with MLA ≤ 6 mm 2, whereas iFR failed to identify in 38% (6/16) of cases where MLA was ≤ 6 mm 2. The authors conclude the FFR may be more suitable than iFR for left main assessment.
Limitations of this study include a small sample size (34 patients), and that within this small group only 32% (11/34) had discordant iFR and FFR, which makes drawing widespread conclusions difficult. It is possible that with a larger sample size, the discrepancy between iFR and FFR, with regards to correlation with IVUS, may become less apparent. In addition, this study did not correlate these findings with clinical outcomes, or with another “gold standard” study (e.g. PET).
Advocates favoring FFR over iFR might point to these results as evidence that FFR is superior to iFR in LMCA assessment, as the authors do. Insofar as predicting IVUS MLA ≤ 6 mm 2, this would be true, something also apparent from prior studies. , However, considering the fact that the IVUS MLA ≤ 6 mm 2 cutoff was originally validated against FFR, it is not at all surprising that FFR better predicts IVUS MLA ≤ 6 mm 2 than iFR. The absence of clinical outcomes in the present study stands in contrast to other studies demonstrating the clinical safety of deferral of LMCA lesions with iFR.
As a result, the present study largely reinforces the inaccuracy of angiography to determine LMCA lesion significance, while also reiterating the known ability of FFR to detect IVUS MLA ≤ 6 mm 2. The study also demonstrates the known discordance between iFR and FFR, especially in high-flow arteries such as the LMCA and LAD. Data on what to do when data are discordant, remains scarce. The iLITRO strategy of utilizing IVUS as a tiebreaker for discordant FFR and iFR values is reasonable. Ultimately all of these diagnostic tests have both value and limitations, and should serve as adjuncts to clinical judgement.
CRediT authorship contribution statement
Arnold Seto: Conceptualization, Writing– original draft, Writing– review & editing. Derek Antoku: Writing– original draft.
Declaration of Competing Interest
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Arnold Seto reports a relationship with GE Healthcare that includes: speaking and lecture fees. Arnold Seto reports a relationship with Terumo Medical Corporation that includes: consulting or advisory and speaking and lecture fees. Arnold Seto reports a relationship with Merit Medical Systems Inc that includes: consulting or advisory and speaking and lecture fees. Arnold Seto reports a relationship with Getinge AB that includes: speaking and lecture fees. Arnold Seto reports a relationship with Frond Medical that includes: equity or stocks. Arnold Seto reports a relationship with Summacor that includes: equity or stocks. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Editorial on: AJC- D -25-02053R2. Comparison of Anatomical and Physiological Indices of Angiographically Intermediate Left Main Coronary Artery Stenoses.
References
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
