Fractional Flow Reserve Determination During Cardiac Catheterization

Introduction to FFR

The American Heart Association recommends that fractional flow reserve (FFR) can be determined during cardiac catheterization using a pressure wire to measure the ratio of distal coronary pressure to aortic pressure during maximal hyperemia 1, 2
FFR is a well-validated, accurate, and objective index for assessing lesion-specific physiological stenosis severity and predicting long-term outcomes 3
FFR measures the maximum achievable myocardial blood flow in the presence of a coronary artery stenosis as a percentage of the maximum blood flow in a hypothetically normal artery 4
The normal value of FFR is 1.0 for every patient and every coronary artery 4

The standardized procedure for FFR measurement includes catheter selection, where guiding catheters without distal side holes are required for research measurements 3
Pressure wire insertion involves inserting the pressure sensor guide wire into the guide catheter and equalizing the pressures registered by the guiding catheter and pressure wire 2
Wire advancement requires advancing the pressure wire sensor to the distal two-thirds of the coronary artery, at least 2-3 cm distal to the index lesion, and documenting the final position angiographically 2
Inducing maximal hyperemia involves administering intracoronary nitrates and intravenous adenosine at 140 μg/kg/min for at least 2 minutes 5, 2
FFR calculation is done as the ratio of distal coronary pressure (Pd) to aortic pressure (Pa) at maximal hyperemia, with the nadir of Pd/Pa ratio during hyperemia representing the FFR value 2, 6

An FFR ≤0.75 is associated with inducible ischemia (specificity 100%) 4
An FFR ≥0.80 indicates absence of inducible ischemia in most patients (sensitivity 90%) 4
For research purposes, a single cutoff value of 0.80 is proposed, with a "gray zone" between 0.75 and 0.80 requiring clinical judgment 1

Catheter ventricularization/damping can impair coronary flow during hyperemia, and solution involves disengaging the guiding catheter from the ostium during measurement 7
Pressure signal drift can be detected by parallel pressure signals with similar morphology throughout diastole and systole, and solution involves pulling back the sensor to equalize pressures and repeat measurements 7
Diffuse disease vs. focal lesions can be differentiated using pullback tracing, which helps identify gradual pressure increase or abrupt changes 7
Pseudostenosis can occur in tortuous vessels where the wire itself creates artifacts, rendering FFR measurements uninterpretable 7

High reproducibility and low intra-individual variability make FFR a reliable measure 4
FFR is independent of gender, CAD risk factors, heart rate, blood pressure, and contractility, providing a well-defined cutoff value with a narrow "gray zone" 4, 1

The American College of Cardiology and American Heart Association recommend FFR for assessing intermediate coronary stenoses (30-70% luminal narrowing) in patients with anginal symptoms, with a Class IIa recommendation (Level of Evidence: A) 8, 9, 10, 11
The European Society of Cardiology guidelines recommend wire-based intracoronary pressure measurement to calculate FFR for intermediate stenoses (40-90% for non-left main stenoses) to improve risk assessment and clinical decision-making 12
FFR measures the ratio of distal coronary pressure to aortic pressure during maximal hyperemia, and a value of ≤0.80 indicates hemodynamically significant stenosis that causes ischemia 8, 9

The FAME trial demonstrated that FFR-guided PCI resulted in significantly lower composite event rates (death, MI, repeat revascularization) at 1 year compared to angiography-guided PCI: 13.2% vs 18.3% (P=0.02) 8, 9
FFR-guided PCI resulted in fewer stents placed (1.9±1.3 vs 2.7±1.2, P=0.001) without adverse outcomes 8, 9
Deferring PCI for intermediate lesions with FFR >0.75 results in excellent outcomes with event rates <10% over 2-year follow-up 13, 14

The American College of Cardiology recommends FFR as an alternative to noninvasive functional testing when such studies are absent or ambiguous 8, 9
The European Society of Cardiology guidelines recommend FFR for intermediate stenoses to improve risk assessment and clinical decision-making 12