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OBJECTIVES: To review the technical limitations of available pressure-wires, present the design evolution of a nitinol fiber-optic pressure wire and to summarize the First-in-Man (FIM) O2 pilot study results. BACKGROUND: Despite increasing use of physiology assessment of coronary lesions, several technical limitations persist. We present technical details, design evolution and early clinical results with a novel 0.014" nitinol fiber-optic based pressure-wire. METHODS AND RESULTS: The 0.014' OptoWire™ (Opsens Medical, Quebec, Canada) was designed to combine improved handling properties compared to standard pressure-wires and to offer extremely reliable pressure recording and transmission due to fiber-optic properties compared to piezo-electric sensors and electrical wires. In vitro assessment showed that OptoWire™ steerability, pushability and torquability properties were closer to regular PCI wires than standard electrical pressure wires. In the First-in-Man O2 study, 60 patients were recruited at 2 centers in Canada. A total of 103 lesions were assessed with the OptoWire™ and OptoMonitor™, 75 lesions at baseline and 28 lesions post-PCI (without disconnection). In all crossed lesions (n = 100, 97%), mean Pd/Pa and FFR could be adequately measured. In 11 cases assessed successively with OptoWire™ and Aegis™ (Abbott Vascular, USA) bland-Altman analysis showed a mean difference of 0.002 ± 0.052 mmHg (p = .91) for Pd/Pa and 0.01 ± 0.06 for FFR calculation (p = .45). There was no device-related complication. Upon these initial results, several design changes aimed to improve overall performance including torquability, stiffness, resistance to kink and pressure drift were completed. CONCLUSION: The novel 0.014" fiber-optic OptoWire™ provides superior wire handling with reduced risk of pressure drift allowing reliable pre- and post-PCI physiology assessment.
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BACKGROUND: Invasive functional assessment is a mainstay in the management of patients with coronary artery disease (CAD), but there is uncertainty on the comparative accuracy of diagnostic indices of functional significance. We aimed to validate the diagnostic performance of a novel non-hyperemic diastolic pressure ratio (dPR). METHODS: We performed a retrospective analysis including two separate registries (VERIFY 2, Latina, Italy) of patients in whom functional indices were measured for lesions with angiographically moderate severity. On top of fractional flow reserve, distal coronary pressure (Pd)/aortic pressure (Pa) ratio, instantaneous wave-free ratio (iFR) and diastolic pressure ratio (dPR) were computed using a novel dedicated algorithm over 4 consecutive beats. Agreement/discrepancy between indexes was appraised Bland-Altman analysis, area under the receiver operating characteristic curve (AUC), and unsupervised machine learning. RESULTS: A total of 525 lesions from 479 patients were included. The novel dPR was highly correlated with iFR (R2=0.99, P<0.001), with a mean difference of -0.004±0.014. The diagnostic performance of dPR (best cutoff value: ≤0.89) against iFR was as follows: accuracy =96%; sensitivity =94%; specificity =97%; positive-predictive value =94%; and negative-predictive value =96%. Additionally, AUC to predict iFR≤0.89 was 0.99, which was significantly higher than that of Pd/Pa (0.97, P<0.001). In the iFR range of 0.85-0.93 ("grey zone"), the diagnostic performance was well maintained (accuracy =91%; sensitivity =87%; specificity =93%; and AUC=0.96). Results were supported also by unsupervised learning analysis. CONCLUSIONS: This multicenter registry suggests this novel dPR algorithm provides results that are numerically equivalent to iFR. Pending further studies, physicians may consider using this novel dPR algorithm to gauge the functional significance of a coronary lesion.