From the Guidelines
Coronary fractional flow reserve (FFR) studies are indicated in patients who have undergone CT coronary angiography when there is intermediate coronary stenosis (typically 40-70% narrowing) and the functional significance of these lesions needs to be determined, as recommended by the 2024 ESC guidelines for the management of chronic coronary syndromes 1.
Indications for FFR Studies
The following are indications for FFR studies:
- Intermediate coronary stenosis (50% to 70% diameter stenosis) as stated in the 2011 ACCF/AHA/SCAI guideline for percutaneous coronary intervention 1
- Ambiguous CT findings
- Multiple lesions present
- Discordance between a patient's symptoms and CT findings
- Risk stratification needed before deciding on revascularization versus medical therapy
Procedure and Interpretation
The procedure involves measuring pressure differences across a stenosis during maximum hyperemia (usually induced with adenosine), with an FFR value ≤0.80 generally indicating a hemodynamically significant lesion that would benefit from intervention 1.
Clinical Utility
FFR studies have been shown to be accurate and demonstrate excellent agreement with invasive FFR, as stated in the CAD-RADS 2.0 document 1. The technique has also been shown to improve catheterization lab efficiency and increase risk associated with an CT-FFR ≤0.80.
Recommendations
The 2024 ESC guidelines recommend selective assessment of functional severity of intermediate diameter stenoses using FFR/iFR (significant ≤0.8 or ≤0.89) to guide the decision to revascularize 1. The CAD-RADS 2.0 document suggests possible ICA referral for a symptomatic patient in the setting of an appropriate clinical context for coronary revascularization and the designation of “ID” (positive ischemia) for a lesion-specific value ≤0.75 in a vessel large enough for percutaneous coronary intervention (PCI) 1.
From the Research
Indications of CFFR Studies
The indications of CFFR (Coronary Computed Tomography-Derived Fractional Flow Reserve) studies in a patient who has undergone CT coronary angiography are:
- To assess the functional significance of coronary artery stenoses 2, 3
- To guide downstream management in patients with intermediate stenosis (30% to 70%) 2
- To identify patients who do not require further diagnostic testing or intervention (FFRCT >0.80) from higher-risk patients (FFRCT ≤0.80) who may need further testing with invasive coronary angiography and possibly intervention 2
- To plan percutaneous coronary interventions (PCI) by assessing lesion-specific ischemia, planning stent locations and sizes, and using virtual remodeling of the lumen (virtual stenting) to assess the functional impact of PCI 4
Key Findings
- FFRCT is effective in differentiating patients who do not require further diagnostic testing or intervention from higher-risk patients who may need further testing with invasive coronary angiography and possibly intervention 2
- The diagnostic accuracy of CTCA, QCT, CCA, and QCA to detect a hemodynamically significant coronary lesion is limited, and FFR measurement is a more accurate method to determine the hemodynamic significance of a coronary stenosis 3
- Angiography-derived FFR has emerged as a non-invasive technique to assess the functional significance of coronary artery stenoses, and its clinical applications include assessing intermediate coronary lesions and guiding revascularization decisions 5
Clinical Applications
- CFFR studies can be used to diagnose and treat coronary artery disease (CAD) in patients with stable chest pain 2, 6
- FFRCT can be used to assess the hemodynamic significance of coronary stenoses and guide revascularization decisions 3, 6
- CTA and FFRCT can be used to plan PCI by assessing lesion-specific ischemia, planning stent locations and sizes, and using virtual remodeling of the lumen (virtual stenting) to assess the functional impact of PCI 4