April 28, 2026Journal of the American College of Cardiology232 citations
FIRST: Fractional Flow Reserve and Intravascular Ultrasound Relationship Study
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Key Result
An IVUS minimum lumen area <3.07 mm2 was the best overall threshold for identifying FFR <0.8, showing moderate accuracy (AUC 0.65) that improved with reference vessel-specific analyses.
Study Design
Type
Observational (n=350)
Multicenter
Yes
PICO
P
Population
Intermediate coronary lesions (n=350)
I
Intervention / Comparator
Intravascular ultrasound (IVUS) vs Fractional flow reserve (FFR)
O
Primary Outcome
Optimal minimum lumen area (MLA) by IVUS correlating with FFR <0.8 — AUC 0.65
Main Result
Effect estimate: AUC 0.65
Limitations
- The utility of IVUS MLA as an alternative to FFR to guide intervention in intermediate lesions may be limited in accuracy and should be tested clinically.
Abstract
OBJECTIVES: FIRST (Fractional Flow Reserve and Intravascular Ultrasound Relationship Study) aimed to determine the optimal minimum lumen area (MLA) by intravascular ultrasound (IVUS) that correlates with fractional flow reserve (FFR) and to assess the correlation between virtual histology IVUS and FFR for intermediate coronary lesions. BACKGROUND: FFR is considered the gold standard for assessing intermediate coronary lesions. Measurements of ≤0.8 are considered clinically significant and indicative of physiological ischemia. METHODS: FIRST is a multicenter, prospective, international registry of patients with intermediate coronary lesions, defined as 40% to 80% stenosis by angiography. In total, 350 patients (367 lesions) were enrolled at 10 U.S. and European sites. Patients were followed through hospital discharge. RESULTS: Overall, an MLA 3.5 mm. FFR correlated with plaque burden (r = -0.220, p < 0.001) but not with other plaque morphology. CONCLUSIONS: Anatomic measurements by IVUS show a moderate correlation with the FFR values. The optimal cutoff for an MLA to FFR <0.8 is vessel dependent. Plaque morphology characteristics do not correlate with FFR. The utility of IVUS MLA as an alternative to FFR to guide intervention in intermediate lesions may be limited in accuracy and should be tested clinically. (Fractional Flow Reserve and Intravascular Ultrasound Relationship Study FIRST; NCT01153555).
Cite This Study
Waksman et al. (2013) conducted an observational in Intermediate coronary lesions (n=350). Intravascular ultrasound (IVUS) vs. Fractional flow reserve (FFR) was evaluated on Optimal minimum lumen area (MLA) by IVUS correlating with FFR <0.8 (AUC 0.65). An IVUS minimum lumen area <3.07 mm2 was the best overall threshold for identifying FFR <0.8, showing moderate accuracy (AUC 0.65) that improved with reference vessel-specific analyses.