Invasive Coronary Physiological Measurements for Guiding Revascularization Decisions

Diagnostic Techniques

The European Society of Cardiology recommends using FFR (Fractional Flow Reserve) and iFR (Instantaneous Wave-Free Ratio) for guiding revascularization decisions in intermediate coronary lesions, with both receiving Class I, Level A guideline recommendations 1, 2
FFR is a pressure-derived index that measures the maximum achievable blood flow in a stenotic coronary artery, calculated as FFR = Pd/Pa during maximal hyperemia, with a normal value of 1.0 in every patient and every coronary artery 3, 6
The established ischemic threshold is FFR ≤0.80, which indicates hemodynamically significant stenosis requiring revascularization, as recommended by the European Heart Journal 1, 2, 5
iFR is a resting pressure-only index that does not require adenosine administration, with a threshold of ≤0.89 indicating hemodynamically significant stenosis requiring revascularization, as recommended by the European Heart Journal 1, 2, 7

FFR-guided PCI has demonstrated superior clinical outcomes compared to angiography-guided PCI, with significantly lower rates of death, MI, and repeat revascularization, as shown in the FAME trial 5
The American College of Cardiology and the European Society of Cardiology recommend using FFR and iFR for guiding revascularization decisions, with Class I, Level A recommendations for both 1, 2
iFR use was associated with lower rates of procedure-related chest pain and shorter procedural time compared to FFR, as demonstrated in the DEFINE-FLAIR and iFR-SWEDEHEART trials 7

Guiding catheters without distal side holes are required for accurate research measurements, and proper pressure equalization between the guiding catheter and pressure wire must be performed before wire advancement 3, 5, 6
Intracoronary nitrates should be administered before measurements, as recommended by the European Heart Journal 2
Catheter ventricularization/damping and pressure signal drift can impair coronary flow during hyperemia, and solutions require disengaging the guiding catheter from the ostium during measurement and pulling back the sensor to equalize pressures, respectively 5