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CARDIOVASCULAR
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RFR—Resting Full Cycle Ratio

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.1 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.1

Touchscreen showing resting full-cycle ratio (RFR) hemodynamic assessment

Measuring RFR

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.2

Resting full-cycle ratio (RFR) finds the lowest value of Pd/Pa, whether in diastole or systole

Advantage of RFR

"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 0.89:1,3,4

  • When RFR ≤ 0.89, treatment with percutaneous coronary intervention (PCI) may be beneficial
  • When RFR > 0.89, deferral of PCI may be beneficial
The cutoff for resting full-cycle ratio (RFR™) is 0.89, while the cutoff for FFR is 0.80

RFR Compared To Other Resting Indices

All resting pressure-derived indices closely correlate with one another, revealing the same discriminatory ability to guide intervention.2 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.4

All resting pressure-derived indexes (instantaneous wave-free ratio,‡ RFR, dPR‡, and DFR‡) closely correlated with one another

Here are the cutoff values for the various non-hyperemic pressure ratios.5

All resting pressure-derived indexes (instantaneous wave-free ratio,‡ RFR, dPR‡, and DFR‡) closely correlated with one another

Key RFR Findings

RFR has been studied in over 3,500 lesions and 2,500 patients, showing clinical accuracy and outcomes.

Major RFR Studies

  Number of Lesions Number of Patients
Re-VALIDATE RFR6 501 431
VALIDATE RFR1 672 504
ILUMIEN I + PREDICT3 313 299
IRIS-FFR7 1,102 926
3V FFR-FRIENDS2 1,024 435
Total 3,612 2,595

Uses of FFR vs Non-Hyperemic Pressure Ratio (RFR)?8

Uses of Non-Hyperemic Index (RFR)
  Non-Hyperemic Index FFR
Tandem Lesions9 +++ +
Diffuse Lesions10 +++ +
Left Anterior Descending11 +++ ++
Acute Coronary Syndrome12 +++ ++
Equivalent Assessment
Multi-Vessel Disease13 +++ +++
Diabetes14 +++ +++
Uses of FFR
Left Main Coronary Artery15 - +++
Systolic Dysfunction16 - +++
Post-PCI Side Branch Interrogation17 - +++
Post-PCI Assessment18 - +++

‡ Indicates a trademark of a third party company or its respective owner.

References

  1. Svanerud J, Ahn JM, Jeremias A, et al. Validation of a novel non-hyperaemic index of coronary artery stenosis severity: the Resting Full-cycle Ratio (VALIDATE RFR) study. EuroIntervention. 2018;14:806-814.
  2. Lee JM, Choi KH, Park J, et al. Physiological and clinical assessment of resting physiological indexes. Circulation. 2019;139:889-900. doi: 10.1161/CIRCULATIONAHA.118.037021.
  3. Jeremias A, et al. Resting full-cycle ratio (RFR): a novel physiologic index compared to Fractional Flow Reserve (FFR) in assessing the hemodynamic severity of a coronary stenosis: ILUMIEN I + PREDICT. EuroPCR 2018.
  4. Ahn JM, et al. IRIS FFR: prognostic performance of five resting pressure-derived indexes of coronary physiology. TCT 2018.
  5. Ali ZA. Invasive assessment of coronary physiology is here to stay. TCT 2019.
  6. Kumar G, Desai R, Goreet A, al. RE-VALIDATE: REal world VALIDATion of the non-hyperemic InDex of coronary Artery sTEnosis severity: resting full-cycle ratio (RFR) – RE-VALIDATE RFR. CRT 2019.
  7. Data on file at Abbott.
  8. Ali Z. Invasive Assessment of Coronary Physiology Is Here to Stay! TCT 2019.
  9. Kikuta Y, Cook CM, Sharp ASP, et al. Pre-angioplasty instantaneous wave-free ratio pullback predicts hemodynamic outcome In humans with coronary artery disease: primary results of the International MulticenteriFR GRADIENT Registry. J Am Coll Cardiol Intv. 2018;11:757-767.
  10. Jeremias A, Davies JE, Maehara A, et al. Blinded physiological assessment of residual ischemia after uccessful angiographic percutaneous coronary intervention: the DEFINE PCI study. JACC Cardiovasc Interv. 2019;12(20):1991-2001.
  11. Sen S, Ahmad Y, Dehbi HM, et al. Clinical eventsa after deferral of LAD revascularization following physiological coronary assessment. J Am Coll Cardiol. 2019;73(4):444-453.
  12. Escaned J, Ryan N, Mejía-Rentería H, et al. Safety of the deferral of coronary revascularization on the basis of instantaneous wave-free ratio and fractional flow reserve measurements in stable coronary artery disease and acute coronary syndromes. JACC Cardiovasc Interv. 2018;11(15):1437-1449.
  13. Escaned J, Collet C, Ryan N, et al. Clinical outcomes of state-of-the-art percutaneous coronary revascularization in patients with de novo three vessel disease: 1-year results of the SYNTAX II study. Eur Heart J. 2017;38(42):3124-3134.
  14. DEFINE-FLAIR Trial Investigators. Comparison of major adverse cardiac events between instantaneous wave-free ratio and fractional flow reserve–guided strategy in patients with or without type 2 diabetes. JAMA Cardiol. 2019;4(9):857-864.
  15. Mallidi J, Atreya AR, Cook J, et al. Long-term outcomes following fractional flow reserve-guided treatment of angiographically ambiguous left main coronary artery disease: a meta-analysis of prospective cohort studies. Catheter Cardiovasc Interv. 2015;86(1):12-18.
  16. Di Gioia G, De Bruyne B, Pellicano M, et al. Fractional flow reserve in patients with reduced ejection fraction. Eur Heart J. 2020;41(17):1665-1672.
  17. Koo BK, Kang HJ, Youn TJ, et al. Physiologic assessment of jailed side branch lesions using fractional flow reserve. J Am Coll Cardiol. 2005;46(4):633-637.
  18. Johnson NP, Tóth GG, Lai D, et al. Prognostic value of fractional flow reserve: linking physiologic severity to clinical outcomes. J Am Coll Cardiol. 2014;64(16):1641-1654. doi: 10.1016/j.jacc.2014.07.973.

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