Approaches to Guided PCI

Approaches to Guided PCI


Fractional flow reserve, or FFR, is a technique
for assessing the severity of a coronary artery stenosis in preparation for possible PCI of
the lesion. FFR uses a pressure wire passed across the
stenotic lesion and measures the mean pressure, both proximal and distal to the stenosis, during
the entire cardiac cycle. As a part of the procedure, the vasodilator
adenosine is administered. However, adenosine is not well-tolerated by
all patients and can cause chest pain, shortness of breath, and other symptoms. The instantaneous wave-free ratio, or iFR,
is a technique for assessing stenosis severity that does not require the use of adenosine. iFR is calculated during only one part of
the cardiac cycle in mid- to late-diastole. Two new trials, the iFR-SWEDEHEART study and
the DEFINE-FLAIR study, compared the efficacy and safety of iFR and FFR-guided coronary
revascularization. The IFR-SWEDEHEART study, which was open label,
randomized 2037 patients with stable angina or acute coronary syndrome. The DEFINE-FLAIR study was a blinded trial
that randomized 2492 patients with coronary artery disease. In both trials, any artery with an angiographic
stenosis of intermediate severity was evaluated for possible revascularization. Study investigators in both trials hypothesized
that iFR would be non-inferior to FFR with respect to the primary endpoint, which was
a composite of all-cause mortality, non-fatal myocardial infarction, and unplanned revascularization
at 1 year. In the iFR-SWEDEHEART study, the primary endpoint
occurred in 6.7% of the iFR group and 6.1% of the FFR group; the 95% confidence interval
for the risk difference fell within the pre-specified non-inferiority margin of 3.2%. In the DEFINE-FLAIR study, the primary endpoint
occurred in 6.8% of the iFR group and 7.0% of the FFR group; and the 95% confidence interval
for the risk difference fell within the pre-specified non-inferiority margin of 3.4%. In both studies, significantly more patients
in the FFR group than in the iFR group reported procedural symptoms owing to the administration
of adenosine. Both studies conclude that, one year after
percutaneous coronary intervention in patients with coronary disease, iFR guided revascularization
was non-inferior to FFR guided revascularization with respect to adverse cardiac events. Full trial results are available at NEJM.org.

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