A novel fiber-optic based 0.014″ pressure wire: Designs of the OptoWire™, development phases, and the O2 first-in-man results

Recent Progress in MEMS Fiber-Optic Fabry-Perot Pressure Sensors

Pressure sensing plays an important role in many industrial fields; conventional electronic pressure sensors struggle to survive in the harsh environment. Recently microelectromechanical systems (MEMS) fiber-optic Fabry-Perot (FP) pressure sensors have attracted great interest. Here we review the basic principles of MEMS fiber-optic FP pressure sensors and then discuss the sensors based on different materials and their industrial applications. We also introduce recent progress, such as two-photon polymerization-based 3D printing technology, and the state-of-the-art in this field, e.g., sapphire-based sensors that work up to 1200 °C. Finally, we discuss the limitations and opportunities for future development.

Fractional flow reserve and non-hyperemic indices: Essential tools for percutaneous coronary interventions

Hemodynamical evaluation of a coronary artery lesion is an important diagnostic step to assess its functional impact. Fractional flow reserve (FFR) received a class IA recommendation from the European Society of Cardiology for the assessment of angiographically moderate stenosis. FFR evaluation of coronary artery disease offers improvement of the therapeutic strategy, deferring unnecessary procedures for lesions with a FFR > 0.8, improving patients' management and clinical outcome. Post intervention, an optimal FFR > 0.9 post stenting should be reached and > 0.8 post drug eluting balloons. Non-hyperemic pressure ratio measurements have been validated in previous studies with a common threshold of 0.89. They might overestimate the hemodynamic significance of some lesions but remain useful whenever hyperemic agents are contraindicated. FFR remains the gold standard reference for invasive assessment of ischemia. We illustrate this review with two cases introducing the possibility to estimate also non-invasively FFR from reconstructed 3-D angiograms by quantitative flow ratio. We conclude introducing a hybrid approach to intermediate lesions (DFR 0.85-0.95) potentially maximizing clinical decision from all measurements.

White light interference demodulation of optical fiber Fabry-Perot micro-pressure sensors based on the Karhunen-Loeve transform and singular value decomposition

In this paper, the Karhunen-Loeve transform (KLT) and wavelength domain interferometric spectral singular value decomposition (SVD) are used for the first time to demodulate the pressure of an optical fiber Fabry-Perot (F-P) micro-pressure sensor, and the feasibility of the proposed method is demonstrated experimentally. The eigenvalue decomposition of the dominant frequency part of the beam-domain interferometric spectrum after the fast Fourier transform (FFT) is performed using KLT, and the singular value decomposition of the wavelength domain interferometric spectrum is additionally performed using SVD. Both methods use high-order eigenvalues as a new metric and then derive the relation between the new metric and the reference pressure. The two demodulation methods are experimentally compared, and we used an optical fiber F-P pressure sensor with unknown structure and material for pressure measurements. Even though the interferometric spectral signal is acquired using a coarse spectrometer (2.5 nm wavelength resolution), one can still achieve high demodulation accuracy with both algorithms. However, the SVD demodulation accuracy decreases significantly after reducing the spectral data points in the wavelength domain from 1566 to 783. KLT still has high demodulation accuracy and linearity after spectral data points are reduced from 1024 to 256 in the wavenumber domain. The satisfactory linearity of the measured pressure versus reference pressure and low reading errors validate the feasibility of the proposed demodulation algorithm.

A novel algorithm for the computation of the diastolic pressure ratio in the invasive assessment of the functional significance of coronary artery disease

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.

Assessing the Accuracy of a second-generation optical sensor pressor wire in a wire to wire comparison (The ACCURACY study)

BACKGROUND

The phenomenon of "pressure drift" increases uncertainty about the correct FFR value. Redesigned and incorporating an optical pressure sensor, the "OptoWire Deux™" is purported to be less prone to the pressure drift seen with piezoelectric coronary pressure wires. The aim of this first in vivo real-world clinical study is to evaluate the performance of OptoWire Deux™ in terms of measurements agreement and propensity to pressure drift in a wire to wire comparison.

METHODS

This is a single center, prospective, non-blinded clinical investigation enrolling 45 consecutive patients with a clinical indication for coronary lesion FFR assessment. Lesions were either simultaneously assessed with two optical sensor pressure wires (OSPW) (Group O-O; 30 patients, 34 lesions) or one OSPW and one piezoelectric pressure wire (PEPW) simultaneously (Group O-P; 15 patients, 15 lesions). Significant drift was defined as a pressure ratio deviation of >0.03.

RESULTS

Mean FFR measurements in Group OO were not statistically different between the two sets of OSPW (overall 0.84±0.10; P = 0.52). In Group OP, however, mean FFR measurement with PEPW (0.85±0.09) was numerically lower than that observed with the OSPW (0.88±0.08; P = 0.09). Level of agreement using the Bland-Altman method was higher when 2 OSPW were used for FFR assessment (-0.002 95% CI [-0.033,0.029] vs. 0.026 95% CI [-0.078, 0.130], respectively). The rate of drift was significantly lower with an OSPW compared to a PEPW (4.8% vs. 26.7% respectively, P = 0.02).

CONCLUSION

The optical sensor guidewire showed a high level of readings' agreement after simultaneous usage of 2 optical sensor guidewires. There was also significantly less drift when compared to a piezoelectric guidewire.