Validation of Resting Diastolic Pressure Ratio Calculated by a Novel Algorithm and Its Correlation With Distal Coronary Artery Pressure to Aortic Pressure, Instantaneous Wave–Free Ratio, and Fractional Flow Reserve

Abstract

Background: Instantaneous wave–free ratio (iFR) offers a reliable non–hyperemic assessment of coronary physiology but requires dedicated proprietary software with a fully automated algorithm. We hypothesized that dPR (diastolic pressure ratio), calculated with novel universal software, has a strong correlation with iFR, similar diagnostic accuracy relative to resting distal coronary artery pressure/aortic pressure and fractional flow reserve (FFR). Methods and Results: The dPR study is an observational, retrospective, single-center cohort study including patients who underwent iFR or FFR. Dedicated software was used to calculate the dPR from Digital Imaging and Communications in Medicine (DICOM) pressure waveforms. The flat period on the pressure difference between sample (dP) to the time difference between the same sample points (dt) signal was used to detect automatically the period, where the resistance is low and constant, and to calculate the dPR, which is an average over 5 consecutive heartbeats. The software was validated by correlating iFR results with dPR. Software validation was done by comparing 78 iFR measurements in 44 patients who underwent iFR. Mean iFR and dPR were 0.91±0.10 and 0.92±0.10, respectively, with a significant linear correlation ( R =0.997; P <0.001). Diagnostic accuracy was tested in 100 patients who underwent FFR. Mean FFR, resting distal coronary artery pressure/aortic pressure, and dPR were 0.85±0.09, 0.94±0.05, and 0.93±0.07, respectively. There was a significant linear correlation between dPR and FFR ( R =0.77; P <0.001). Both distal coronary artery pressure/aortic pressure and dPR had good diagnostic accuracy in the identification of lesions with an FFR ≤0.80 (area under the curve, 0.84; 95% CI, 0.76–0.92 and 0.86; 95% CI, 0.78–0.93, respectively). Conclusions: dPR, calculated by a novel validated software tool, showed a strong linear correlation with iFR. dPR correlated well with FFR with a good diagnostic accuracy to identify positive FFR.

Conversation in cardiology: Is there a need for clinical trials for the nonhyperemic pressure ratios?

“…Theoretical differences in NHPR around 0.01–0.02 are within test–retest variance and, at least to me, are not clinically meaningful. In the study by Ligthart et al, the linear correlation between dPR and iFR was 0.997. In this study and other studies, the area under the curve (AUC) or C‐index values for NHPR are of the order 0.98–0.99.…”

“…As summarized in your editorial, the theoretical concepts of the five NHPRs (Pd/Pa, RFR, iFR, full diastolic pressure ratio, Pd/Pa during flat period of the dP / dt of aortic pressure [dPR], DFR) have been subjected to careful validation, as reflected in the recent publications. Several studies now support numerical and clinical equivalence between the NHPR . These validation studies have, in the main, reported numerical equivalence within the family of NHPR.…”

“…In addition, in the RESOLVE cooperative study that we performed in 1593 core lab assessed measures, there were some differences between Pd/Pa and iFR 5 (Figure 3 Several studies now support numerical and clinical equivalence between the NHPR. 6,[9][10][11][12][13] These validation studies have, in the main, reported numerical equivalence within the family of NHPR. Theoretical differences in NHPR around 0.01-0.02 are within test-retest variance and, at least to me, are not clinically meaningful.…”

“…Theoretical differences in NHPR around 0.01-0.02 are within test-retest variance and, at least to me, are not clinically meaningful. In the study by Ligthart et al, 10 note that the hazard ratios for an increment of 0.1 in each index were 0.514 for iFR, 0.524 for RFR, and 0.587 for dPR.…”

FFR, iwFR und nicht invasive CT-FFR

“…Weitere Analysealgorithmen für Ruhe-Indizes wurden entwickelt, die auf einem ähnlichen Prinzip basieren, aber vom iFR-Algorithmus etwas abweichen. Hierzu gehören ▪ die diastolischen Druckgradienten dPR ("diastolic pressure ratio") [4], teilweise als DFR ("diastolic hyperemia-free ratio") geschützt, sowie ▪ der als RFR ("resting full-cycle ratio") bezeichnete Algorithmus [18], der den maximalen Druckgradient Pd/Pa während des gesamten Herzzyklus identifiziert (ca. 12 % aller Messungen auch in der Systole, vor allem in der rechten Koronararterie [18]) (▶ Abb.…”