Difference Between DFR and FFR
DFR (diastolic fractional flow reserve) and FFR (fractional flow reserve) are essentially measuring the same physiological parameter—the hemodynamic significance of coronary stenosis—but DFR restricts the measurement to only the diastolic phase of the cardiac cycle, while FFR measures across the entire cardiac cycle during maximal hyperemia. 1
Key Technical Distinctions
FFR (Fractional Flow Reserve)
- Whole cardiac cycle measurement during maximal pharmacological hyperemia (typically adenosine-induced)
- Represents the ratio of maximal achievable blood flow in a stenotic artery compared to a normal artery 1
- Calculated as: FFR = Pd/Pa (distal coronary pressure/aortic pressure) during hyperemia
- Requires adenosine administration with associated side effects and costs
- Established cutoff: ≤0.80 indicates hemodynamically significant stenosis 2
DFR (Diastolic Fractional Flow Reserve)
- Diastolic-only segmentation of the pressure measurement
- Based on the physiological principle that coronary blood flow occurs predominantly during diastole 1
- Theoretically might have higher diagnostic accuracy for detecting ischemia since it focuses on the phase when coronary perfusion actually occurs
- Can be measured during hyperemia (diastolic FFR) or at rest (diastolic hyperemia-free ratio)
Clinical Performance and Diagnostic Equivalence
In practice, full-cycle FFR and dFFR have similar diagnostic value with near-equivalent diagnostic accuracy. 1 The VERIFY study post-hoc analysis demonstrated:
- Area under the curve (AUC) of 98% for diastolic FFR predicting FFR ≤0.80 1
- Strong correlation between measurements
Recent Research Findings
More recent studies on the diastolic hyperemia-free ratio (DFR) as a resting index show:
- Strong linear correlation with FFR (r = 0.74-0.80) 3, 4
- Diagnostic accuracy of 83-92% compared to FFR 3, 5
- DFR cutoff ≤0.89 predicts FFR ≤0.80 3, 4
- Discordance occurs in approximately 17-26% of cases 5
Important Clinical Caveats
Gray Zone Problem
The diagnostic accuracy of DFR drops significantly in the gray zone (0.88-0.90), where accuracy is only 40% 5. In these intermediate values, FFR measurement with adenosine may still be necessary for definitive decision-making.
Advantages of DFR Approach
- Avoids adenosine administration (reducing side effects, cost, and procedural time) 4
- Faster measurement
- Patient convenience
When DFR May Be Insufficient
- Discordant results occur in 17-26% of lesions 5
- Particularly unreliable when DFR values fall between 0.88-0.90 5
- In these cases, proceed to adenosine-based FFR for definitive assessment
Practical Algorithm
- Initial assessment: Measure resting DFR
- If DFR <0.86: High likelihood of significant stenosis (86% accuracy) 5
- If DFR >0.93: High likelihood of non-significant stenosis (95% accuracy) 5
- If DFR 0.88-0.90: Proceed to adenosine-based FFR due to poor diagnostic accuracy (40%) in this range 5
The bottom line: While DFR offers convenience by avoiding adenosine, FFR remains the gold standard with Class I guideline recommendations 1, and should be used when DFR results are in the gray zone or when definitive assessment is critical for revascularization decisions.