Original Investigation
Comparison of Different Diastolic Resting Indexes to iFR: Are They All Equal?

https://doi.org/10.1016/j.jacc.2017.10.066Get rights and content
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Abstract

Background

Pressure measurement for the duration of the wave-free period (WFP) is considered essential for resting-state physiological assessment of coronary stenosis severity using the instantaneous wave-free ratio (iFR).

Objectives

The aim of this study was to compare other diastolic resting indexes to iFR.

Methods

In the population of the VERIFY2 (Pd/Pa vs iFR in an Unselected Population Referred for Invasive Angiography) study, iFR calculated by proprietary software (Volcano Harvest, Volcano Corporation, Rancho Cordova, California) was compared with the ratio of resting distal coronary pressure and aortic pressure during the complete duration of diastole (dPR), 25% to 75% of diastole (dPR25–75), and midpoint of diastole (dPRmid), along with Matlab calculated iFR (iFRmatlab) and iFR-like indexes shortening the length of the WFP by 50 and 100 ms (iFR−50ms and iFR−100ms), respectively. Mutual differences, Spearman correlations, area under the curve values from receiver-operating characteristic analyses, and diagnostic performance with respect to iFR and fractional flow reserve (FFR) were calculated for all indexes.

Results

Median iFR in 197 patients with 257 vessels was 0.91 with an interquartile range of 0.87 to 0.95. The mutual differences (± SD) with iFR were 0.006 ± 0.011 (dPR), 0.001 ± 0.007 (dPR25–75), 0.001 ± 0.008 (dPRmid), 0.005 ± 0.009 (iFRmatlab), 0.003 ± 0.008 (iFR−50ms), and 0.001 ± 0.009 (iFR−100ms). Correlations for all indexes with iFR were >0.99 (p < 0.001 for all). Area under the curve values for predicting iFR were >0.99 for all indexes as well. Diagnostic accuracy compared with FFR was 76% to 77% for all indexes including iFR.

Conclusions

All diastolic resting indexes tested were identical to iFR, both numerically and with respect to their agreement with FFR. A numerically equal value to iFR can be determined without restriction to the WFP. Cutoff values, guidelines, and clinical recommendations for iFR can therefore be extended to these other indexes. (Pd/Pa vs iFR in an Unselected Population Referred for Invasive Angiography [VERIFY2]; NCT02377310)

Key Words

coronary physiology
coronary pressure measurements
FFR
iFR
resting indexes
wave-free period

Abbreviations and Acronyms

AUC
area under the curve
dPR
diastolic pressure ratio
FFR
fractional flow reserve
iFR
instantaneous wave-free ratio
IQR
interquartile range
Pa
aortic pressure
Pd
distal coronary pressure
ROC
receiver-operating characteristics curve
WFP
wave-free period

Cited by (0)

Dr. van’t Veer has received a speaker fee from Abbott. Dr. Pijls has served as a consultant for Abbott and Opsens; and has equity in Philips, GE, HeartFlow, and ASML. Dr. Ali has received institutional research grants to Columbia University from St. Jude Medical and Cardiovascular Systems Inc.; and has served as a consultant to St. Jude Medical, ACIST Medical, Cordis, and Boston Scientific. Dr. De Bruyne is shareholder for Siemens, GE, Bayer, Philips, HeartFlow, Edwards Lifesciences, Sanofi, and Omega Pharma; his institution, the Cardiovascular Center Aalst, has received grant support from Abbott, Boston Scientific, Biotronik, and St. Jude Medical; and his institution has received consulting fees on behalf of Dr. De Bruyne from St. Jude Medical, Opsens, and Boston Scientific outside of the submitted work. Dr. Barbato’s institution, the Cardiovascular Research Institute Aalst, has received speaker and consultancy fees from Abbott Vascular and Boston Scientific on his behalf. Dr. Berry and the University of Glasgow hold research and consultancy agreements with Abbott. Dr. Oldroyd has received consultancy and speaker fees from Abbott; and has received research support from Boston Scientific. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. Drs. Berry and Oldroyd contributed equally.

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