Clinical Validation of a Novel Pressure Microcatheter-Based Nonhyperemic Pressure Ratio (SUPREME II Study)

Background: The constant resistance ratio (cRR) is a novel nonhyperemic pressure ratio based on piezoresistive pressure microcatheter (PMC) measurements. With repeated measurements in randomized order of PMC and pressure wire techniques, this study aimed primarily to validate the diagnostic performance of cRR compared with fractional flow reserve (FFR) in coronary lesions of 30% to 90% diameter stenosis. Methods: SUPREME II (Sensor-Equipped Ultrathin Pressure Microcatheter Versus Pressure Wire for Physiological Measurements) was a multicenter, prospective study that included 466 patients (483 vessels) from 11 centers. All target vessels were assessed using both pressure wire and PMC separately in randomized order under resting and hyperemic conditions. The primary end point was the diagnostic accuracy of the cRR using a PMC-based FFR of ≤0.80 as the reference standard. Secondary end points included the cRR "gray zone" of the cRR-FFR hybrid strategy and the proportion of patients in whom diagnosed was achieved without vasodilator use. Results: The optimal cRR cutoff was 0.89, which correctly classified 82.8% of the patients, with a sensitivity and specificity of 87.0% and 80.1%, respectively, and achieved an area under the curve of 0.92 with FFRPMC as reference (area under the curve 0.90 with FFRpressure wire as reference). If FFR was added for decision-making in cases of cRR values between 0.85 and 0.91, a cRR--FFR hybrid strategy achieved a 95.3% agreement with the FFR-only strategy and allowed 68.5% of the patients to not require using vasodilator. Conclusions: In coronary stenosis of 30% to 90% diameter stenosis, cRR measurements were highly feasible. The diagnostic accuracy of cRR with FFRPMC as reference was excellent. Further, a cRR-FFR hybrid strategy may reduce vasodilator use without compromising diagnostic accuracy. Registration: URL: https://clinicaltrials.gov/study/NCT05417763; Unique Identifier: NCT05417763.