Significance of CFR 1.7 on Cardiac CTA
A coronary flow reserve (CFR) of 1.7 on cardiac CTA is abnormal and indicates impaired coronary vasodilatory capacity, suggesting either significant epicardial coronary stenosis, microvascular dysfunction, or diffuse atherosclerotic disease requiring further evaluation and aggressive medical management.
Understanding CFR vs FFR
While your question asks about CFR (coronary flow reserve), it's important to clarify that CFR and FFR are distinct physiological measurements:
- FFR (Fractional Flow Reserve) measures pressure-derived flow limitation across a stenosis, with normal values of 1.0 and an ischemic threshold of ≤0.80 1, 2
- CFR (Coronary Flow Reserve) measures the ratio of maximal hyperemic flow to resting flow, reflecting both epicardial and microvascular function 3
Clinical Significance of CFR 1.7
CFR values below 2.0 are generally considered abnormal, indicating:
- Impaired vasodilatory reserve that may result from epicardial stenosis, microvascular dysfunction, or both 3
- Increased cardiovascular risk, as coronary vasodilatory capacity has prognostic importance 4
- Need for comprehensive evaluation to distinguish between epicardial disease and microvascular pathology 3
Differential Diagnosis
A CFR of 1.7 may indicate:
- Hemodynamically significant epicardial stenosis requiring revascularization consideration 1
- Diffuse atherosclerotic disease causing gradual pressure decline along the vessel length without focal stenosis 3, 5
- Microvascular dysfunction, particularly in patients with hypertension, left ventricular hypertrophy, diabetes mellitus, or female sex 3
- Combined epicardial and microvascular disease 3
Recommended Clinical Approach
Correlate CFR findings with anatomic CTA findings:
- If focal stenosis is present: Consider invasive FFR measurement if revascularization is contemplated, as FFRCT has known limitations and invasive FFR remains the gold standard for decision-making 3
- If diffuse disease pattern without focal stenosis: FFR should not be considered a marker for revascularization; aggressive medical therapy is the primary treatment approach 3
- If normal epicardial arteries: Consider microvascular dysfunction and measure index of microvascular resistance (IMR) if invasive assessment is performed 3
Medical Management
Initiate aggressive medical therapy regardless of revascularization decision:
- Aspirin for antiplatelet effect 3
- High-intensity statin therapy 3
- Antianginal medications as needed for symptom control 3
- Risk factor modification targeting hypertension, diabetes, and other cardiovascular risk factors 3
Important Caveats
- Do not rely solely on non-invasive measurements for revascularization decisions in borderline or complex cases 3, 5
- FFRCT has not been validated in coronary stents, bypass grafts, coronary anomalies, dissection, post-TAVR, unstable angina, or acute/recent myocardial infarction 5
- Gradually decreasing FFRCT values distally without proximal focal lesion specifically indicates diffuse atherosclerosis, not a target for focal revascularization 3, 5