FIRST (Fractional Flow Reserve and Intravascular
Ultrasound Relationship Study) is multicenter registry report with intermediate
coronary lesions, defined as 40% to 80% stenosis by angiography. Totally 350
patients with 367 lesion were enrolled.
FFR is considered gold standard for assessing
ischemia of intermediate lesion, FFR of less than 0.8 is considered indication
for stenting a lesion. Traditionally cutoff value by IVUS to stent an intermediate
lesion was minimal luminal area (MLA) of less than 4.0 mm2 but this
was too generous approach so it is criticized. FIRST trial looked into coralataion
of IVUS MLA with FFR weather same value of 4.0mm2 to be used for all
vessels or does it very with reference vessel diameter (RVD) does “same size
fit all”
FIRST trail showed poor correlation of IVUS MLA with
FFR and also same size does not fit all vessels and also FFR was not helpful in
assessing plaque morphology.
Results
of FIRST correlating with FFR of less than 0.8 were
1. Overall
MLA of less than 3.07 mm2, 64.0% sensitivity, 64.9% specificity
2. Accuracy
improved with reference vessel correlation with MLA
a. MLA
less than 2.4 mm2 was best for reference vessel diameters less than 3.0
mm
b. MLA
less than 2.7 mm2 was best for reference vessel diameters of 3.0 to
3.5 mm
c. MLA
less than 3.6 mm2 was best for reference vessel diameters more than
3.5 mm
3. FFR
correlated with plaque burden but not with other plaque morphology.
Conclusion
As there is poor correlation between FFR and IVUS
MLA it appears IVUS MLA may not be good choice to decide to stent or to defer
stenting of intermediate lesion
Anatomically feasibility can be used by IVUS to
guide PCI of intermediate lesions
