To determine the need for percutaneous coronary intervention, physiology indices such as fractional flow reserve (FFR) and resting full-cycle ratio (RFR) are used to identify functionally significant epicardial coronary stenoses at stress or rest.1
Measure FFR and RFR with PressureWire™ X GuideWire, the world's only2,3 wireless physiology wire with a hydrophilic-coated3 design for exceptional handling performance and accurate measurements reliable readings.4,5
FFR is a measure of blood pressure difference across a coronary artery stenosis to determine if a stenosis is physiologically significant, which can impede oxygen delivery to the heart muscle.1
Coronary angiography is not accurate in guiding the functional significance of stenosis in 34% of cases, compared to FFR.6
FFR-guided percutaneous coronary intervention (PCI) leads to a 35% risk reduction in death and myocardial infarction (MI), compared to relying only on angiography.7
Complete revascularization with PressureWire™ X Guidewire led to a 62% relative risk reduction in major adverse cardiac and cerebrovascular events (MACCE) at 1 year.8 The DANAMI-3-PRIMULTI trial also revealed that untreated “FFR-positive” non-infarct-related artery lesions are associated with a 31% incidence of MACCE at 1 year.8
Abbott's PressureWire™ X Guidewire measures resting full-cycle ratio (RFR), a resting index that can be measured as an alternative to FFR depending on the clinical situation.9 Like FFR, RFR can identify functionally significant epicardial coronary stenosis. Unlike FFR, RFR is a non-hyperemic index that does not require the administration of a vasodilator such as adenosine.9
Clinically equivalent to the instantaneous wave-free ratio (iFR‡) resting index, Abbott's RFR resting index scans through diastole and systole for the lowest pd/pa ratio. Unlike iFR‡ or diastolic pressure ratio (dPR‡), RFR is calculated from the lowest value of Pd/Pa over the entire cardiac cycle.10
"The major advantage of RFR over iFR‡ is that RFR does not require identification of a specific landmark or selection of a specific time point during diastole. By calculating the minimum Pd/Pa over the entire cardiac cycle, RFR calculates the maximum pressure gradient across the stenosis during resting status."
– Lee, et al. Circulation 2019
The cutoff value of RFR is 0.89:9,11,12
In patients with multiple sequential stenoses or diffuse lesions, pullback pressure assessment can identify lesions with functional significance. RFR can be calculated along the entire length of a stenotic vessel using pullback, which measures pressure gradient at any given location.9
All resting pressure-derived indices closely correlate with one another, revealing the same discriminatory ability to guide intervention.10 The large IRIS-FFR retrospective study (1,506 patients, 1,833 lesions) examined deferred lesion failure among 5 resting indices—resting Pd/Pa, iFR‡, RFR, dPR‡, and DFR‡—and concluded that all resting indices had similar outcomes in deferred lesions.12
Here are the cutoff values for the various non-hyperemic pressure ratios.14
RFR has been studied in over 3,500 lesions and 2,500 patients, showing clinical accuracy and outcomes.
Drift is a phenomenon that affects the accuracy of most pressure measurement devices.17 Accuracy is particularly critical for resting ratios, as clinical decisions from resting ratios are more impacted by drift than FFR.18,19
Compared to the hyperemic state, smaller separation between Pd and Pa at rest means even relatively small amounts of drift can lead to stenosis misclassification compared to FFR. That’s why it critical to detect even the slightest difference of pressure.
| Uses of FFR | ||
|---|---|---|
| Non-Hyperemic Index | FFR | |
| Left Main Coronary Artery20 | – | +++ |
| Systolic Dysfuntion21 | – | +++ |
| Post-PCI Side Branch Interrogation22 | – | +++ |
| Post-PCI Assessment23 | – | +++ |
| Equivalent Assessment | ||
| Multi-Vessel Disease24 | +++ | +++ |
| Diabetes25 | +++ | +++ |
| Uses of Non-Hyperemic Index (RFR) | ||
| Tandem Lesions26 | +++ | + |
| Diffuse Lesions27 | +++ | + |
| Left Anterior Descending28 | +++ | ++ |
| Acute Coronary Syndrome29 | +++ | ++ |
Chart courtesy of Ziad Ali, MD.
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