Pullback Pressure Gradient (PPG) Global Registry
Pullback Pressure Gradient (PPG) Global Registry
The purpose of this study is to determine the predictive capacity of the Pullback Pressure
 Gradient (PPG) index for post-PCI FFR and to determine the impact of the PPG index on
 clinical decision making about revascularization and on clinical outcomes.
A Fractional Flow Reserve (FFR) evaluation comprises measurement of a distal single value and
 a pullback maneuver during hyperemic conditions. The PPGindex is a novel metric derived from
 the FFR pullback curve.3 This metric complements the distal FFR value by informing the
 spatial distribution of epicardial resistance (i.e. focal or diffuse) along the coronary
 vessel. The PPGindex relies on two components: first, the magnitude of pressure drop
 determined as a maximal pressure gradient over 20 millimeters relative to the total vessel
 gradient; and second, the length of functional disease relative to total vessel length. These
 two parameters are weighted equally to provide a metric that ranges from 0 to 1. PPGindex
 values approaching 1 represent functional focal coronary artery disease (CAD) whereas values
 close to 0 represent diffuse functional CAD. Until now, the interpretation of the FFR
 pullback relied on visual assessment. The PPGindex quantifies the pattern of functional CAD
 and has been shown to predict functionally complete revascularization. Percutaneous
 revascularization in vessels with high PPGindex is associated with high post-PCI FFR and vast
 improvement in epicardial conductance whilst PCI in vessels with low PPGindex results in low
 post-PCI FFR. An curvilinear relationship is observed between PPGindex and functional gain
 (i.e. FFR post-PCI minus FFR pre-PCI). The PPGindex, therefore, aims to predict the response
 to PCI in physiological terms.

 Calculation of the PPGindex is indicated in cases with an FFR≤0.80. FFR pullbacks are
 performed under hyperemic conditions at a steady pace during manual pullback. A calculation
 of the PPGindex using the Coroflow console (Coroventis Research Ab, Uppsala, Sweden) is
 available for online use and computes the PPG value immediately after the pullback maneuver.
 This software also includes an automated drift correction. The pullback curve is depicted on
 an dedicated pullback display screen and the pressure gradients are shown per millimeter,
 allowing correlation between the location of pressure step-ups and the anatomical target for
 PCI. In summary, we can distinguish three points where FFR influences the clinical
 decision-making process. First, an FFR ≤0.80 indicates potential benefit of
 revascularization. Second, the pullback curve assesses disease pattern and PPG index value
 quantifies it, helping de physician in the decision about treatment options (e.g. PCI, CABG
 or OMT). And, third, the location of pressure step-ups along the vessels helps plan the PCI
 strategy with respect to coverage of functional disease. A combined FFR and PPG-guided PCI
 strategy has the potential to improve patient selection and enhance procedural planning.

 The purpose of this study is to determine the predictive capacity of the PPG index for
 post-PCI FFR and to determine the impact of the PPG index on clinical decision making about
 revascularization and on clinical outcomes.
Inclusion Criteria:

 -  Consecutive patients with stable coronary artery disease or stabilized acute coronary
 syndrome and invasive FFR measurement ≤0.80.

 Exclusion Criteria:

 -  Angiographic exclusion criteria

 1. Ostial lesions.

 2. Severe vessel tortuosity.

 3. Vessel rewiring deemed 'difficult' by the operator.

 4. Bifurcation with planned two-stent strategy.

 5. NSTEMI culprit vessel.

 6. STEMI

 7. Uncontrolled or recurrent ventricular tachycardia.

 8. Hemodynamic instability

 9. Severe renal dysfunction, defined as an eGFR <30 mL/min/1.73 m2