Physiological Disease Pattern as Assessed by Pull Back Pressure Gradient Index in Vessels With FFR/iFR Discordance
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Updated: May 26, 2025
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Published on: September 27, 2024
Pruthvi C Revaiah1, Tsung-Ying Tsai1, Albert Chinhenzva1
1CORRIB Research Centre for Advanced Imaging and Core Laboratory, University of Galway, Galway, Ireland.
Insights
The physiological pattern of coronary artery disease (CAD) influences discrepancies between fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR). Pull back pressure gradient index (PPGi) helps differentiate focal versus diffuse CAD patterns in discordant cases.
Area of Science:
- Cardiovascular Medicine
- Interventional Cardiology
- Diagnostic Imaging
Background:
- Fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) show discordance in approximately 20% of coronary artery disease (CAD) cases.
- The physiological pattern of CAD, characterized by pull back pressure gradient index (PPGi), may explain these discrepancies.
Purpose of the Study:
- To investigate if the pull back pressure gradient index (PPGi) differs between discordant fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) groups (FFR+/iFR- vs. FFR-/iFR+).
- To evaluate the role of CAD physiological patterns in FFR/iFR discordance.
Main Methods:
- 355 patients with chronic coronary syndrome and intermediate epicardial coronary artery lesions underwent invasive coronary angiography, FFR, iFR, and PPGi analysis.
- Vessels were categorized based on FFR (≤0.80) and iFR (≤0.89) significance and PPGi (≥0.75 for focal, <0.75 for diffuse) patterns.
Main Results:
- FFR and iFR disagreed in 16.7% of cases.
- The median PPGi was significantly lower in the FFR-/iFR+ group (diffuse CAD) compared to the FFR+/iFR- group (focal CAD) (0.65 vs. 0.82; P < 0.001).
- Predominantly focal CAD was associated with FFR+/iFR- (76.3%), while diffuse CAD was associated with FFR-/iFR+ (96.3%).
Conclusions:
- The physiological pattern of coronary artery disease (CAD), as assessed by PPGi, is a significant factor contributing to discordance between FFR and iFR.
- Understanding CAD patterns can help interpret FFR/iFR discrepancies.
Background:
Fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) are discordant in approximately 20% of cases, and it is unclear whether this is influenced by the physiological pattern of coronary artery disease (CAD). The pull back pressure gradient index (PPGi) can objectively characterize the physiological pattern of CADs.
Objectives:
The aim of this study was to evaluate whether PPGi differed in discordant groups (FFR+/iFR- vs FFR-/iFR+).
Methods:
The study enrolled 355 patients (390 vessels) with chronic coronary syndrome who had ≥1 epicardial coronary artery lesion with 40% to 90% diameter stenosis by visual assessment on invasive coronary angiography and had analyzable FFR, iFR, and PPGi derived from quantitative flow ratio. Cutoffs for hemodynamic significance were FFR ≤0.80 and iFR ≤0.89. Vessels were classified as FFR+/iFR+ (n = 103 [26.4%]), FFR-/iFR+ (n = 27 [6.9%]), FFR+/iFR- (n = 38 [9.7%]), and FFR-/iFR- (n = 222 [57%]) groups.
Results:
Median FFR, iFR, and quantitative flow ratio were 0.84 (Q1-Q3: 0.77-0.90), 0.92 (Q1-Q3: 0.88-0.97), and 0.83 (Q1-Q3: 0.73-0.90), respectively. FFR disagreed with iFR in 16.7% of cases (65 of 390). The median PPGi was 0.75 (Q1-Q3: 0.67-0.85). The physiological pattern of CAD was classified according to the PPGi as predominantly physiologically focal (PPGi ≥0.75) in 209 of 390 vessels (53.6%) or diffuse (PPGi < 0.75) in 181 of 390 vessels (46.4%). The median PPGi was significantly lower in FFR-/iFR+ vs FFR+/iFR- vessels (0.65 [Q1-Q3: 0.60-0.69] vs 0.82 [Q1-Q3: 0.75-0.85]; P < 0.001). Predominantly physiologically focal disease was significantly associated with FFR+/iFR- (76.3% [29 of 38]), while predominantly physiologically diffuse disease was significantly associated with FFR-/iFR+ (96.3% [26 of 27] [P < 0.001] for pattern of CAD between FFR+/iFR- and FFR-/iFR+ groups).
Conclusions:
The physiological pattern of CAD is an important influencing factor in FFR/iFR discordance. (Radiographic Imaging Validation and Evaluation for Angio iFR [REVEAL iFR]; NCT03857503).
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