What is the best physiologic tool to assess ischemia in a patient with a 50% mid-Left Anterior Descending (LAD) artery stenosis during Percutaneous Coronary Intervention (PCI)?

FFR is the Best Physiologic Tool to Assess Ischemia During PCI

For a patient undergoing PCI with an uncertain 50% mid-LAD stenosis, fractional flow reserve (FFR) is the best physiologic tool to assess ischemia, as it directly measures the hemodynamic significance of the lesion and has Level A evidence supporting improved clinical outcomes when used to guide revascularization decisions. 1

Why FFR is Superior to Other Options

FFR Provides Direct Physiologic Assessment

• FFR measures the ratio of distal coronary pressure to aortic pressure during maximal hyperemia, representing the maximum achievable myocardial blood flow as a percentage of normal flow 2
• The normal FFR value is 1.0 for every patient and every coronary artery, with FFR ≤0.80 indicating hemodynamically significant stenosis that causes ischemia 1, 2
• FFR is independent of heart rate, blood pressure, contractility, and microcirculatory disturbances, making it highly reproducible 1, 2

Strong Guideline Support for FFR

• ACC/AHA/SCAI guidelines give FFR a Class IIa recommendation (Level of Evidence: A) for assessing intermediate coronary stenoses (30-70% luminal narrowing) in patients with anginal symptoms 1
• The 2024 ESC 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 1
• FFR is specifically recommended as an alternative to noninvasive functional testing when such studies are absent or ambiguous 1

Clinical Outcomes Data Supporting FFR

• 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) 1
• In the FFR-guided group, 37% of lesions had FFR >0.80 and were not stented, resulting in fewer stents placed (1.9±1.3 vs 2.7±1.2, P=0.001) without adverse outcomes 1
• Multiple studies show that deferring PCI for intermediate lesions with FFR >0.75 results in excellent outcomes with event rates <10% over 2-year follow-up 1

Why Other Options Are Inferior

IVUS (Option A) - Anatomic, Not Physiologic

• IVUS provides anatomic information about vessel size and plaque characteristics but does not measure ischemia or hemodynamic significance 1
• IVUS cannot determine whether a stenosis causes ischemia, which is the critical question for revascularization decisions 1

OCT (Option B) - Anatomic, Not Physiologic

• Like IVUS, OCT provides high-resolution anatomic imaging but does not assess the physiologic significance of stenoses
• OCT cannot determine whether intervention is warranted based on ischemia

Coronary CT (Option D) - Not Available During PCI

• Coronary CT angiography is performed before catheterization, not during PCI 3
• While CT-derived FFR (FFR_CT) exists, it is a pre-procedural planning tool, not an intraprocedural assessment method 3, 4
• The patient is already in the catheterization laboratory undergoing PCI, making CT impractical

Stress ECG (Option E) - Not Performed During PCI

• Stress ECG is a noninvasive test performed before catheterization, not during PCI
• Guidelines specifically state that FFR is useful as an alternative when noninvasive functional studies are absent or ambiguous 1
• The patient is already undergoing PCI, making stress testing impractical and unnecessary when FFR can be measured directly

Practical Application for This Case

Why This 50% LAD Stenosis Needs FFR

• Visual angiographic assessment correlates poorly with hemodynamic significance: only 35% of 50-70% stenoses are actually hemodynamically significant by FFR 1
• A 50% stenosis falls squarely in the intermediate range (30-70%) where FFR is specifically recommended 1
• Without FFR, there is a high risk of either unnecessary stenting (if the lesion is not ischemic) or missed treatment (if it is ischemic)

How to Perform FFR in This Case

• Advance a pressure wire sensor to the distal two-thirds of the LAD, at least 2-3 cm distal to the 50% stenosis 2
• Administer intracoronary nitrates and intravenous adenosine at 140 μg/kg/min for at least 2 minutes to induce maximal hyperemia 2
• Calculate FFR as the ratio of distal coronary pressure (Pd) to aortic pressure (Pa) at maximal hyperemia 2
• If FFR ≤0.80, proceed with PCI; if FFR >0.80, defer intervention and continue optimal medical therapy 1

Common Pitfalls to Avoid

• Ensure the guiding catheter is not causing damping during measurement by disengaging it from the ostium during hyperemia 2
• Check for pressure signal drift by pulling back the sensor to equalize pressures if needed 2
• Measure FFR at the appropriate location: 2-3 cm distal to the stenosis, not at the distal vessel tip, to avoid overestimating ischemia 4, 5