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Reliability and Safety of a Side-Branch Jailed Second-Generation Optical-Pressure Guidewire in a Physiology-Guided Bifurcation-PCI In Vitro Model
Abstract
Background. The treatment of a coronary bifurcation with a single stent (the provisional stenting technique) is associated with a good outcome in most cases. In the majority of cases, after provisional stenting technique, a residual significant angiographic stenosis is associated with the absence of ischemia when fractional flow reserve (FFR) is measured. Jailing an optical pressure guidewire in the side branch (SB) could potentially reduce unnecessary SB interventions after provisional stenting technique. The aim of this study was to compare distal pressure to aortic pressure ratio (Pd/Pa) measurements between 2 second-generation optical pressure guidewires in bifurcation treatment—a jailed wire (JW) and a second free-floating wire (FW) advanced into the SB after stenting. Methods. In an in vitro bifurcation hydrodynamic model with pressure sensors, a JW was advanced into the SB and the FW into the main branch. Bifurcation stenting is performed with the proximal optimization technique (POT)-side-POT technique using a 3.0 x 22-mm stent, a 4.0 x 12-mm noncompliant balloon for the POT, and a 2.5 x 12-mm semicompliant balloon for the SB opening. The same steps were performed in a second model where a surgical clamp was placed in the main vessel to lower overall absolute values pressures. Results. A strong correlation was found between JW and FW values (Pearson's coefficient, r=0.91). All wires could be safely retrieved. Conclusion. In bifurcation stenting, the Pd/Pa value of a second-generation optical pressure guidewire jailed in the SB is reliable compared with a FW inserted after stent implantation.
J INVASIVE CARDIOL 2022;34(8):E594-E600. Epub 2022 July 7.
Key words: coronary bifurcation, fractional flow reserve, optical pressure guidewire, side branch
The percutaneous treatment of coronary bifurcations requires a single-stent technique in the majority of procedures.1-4 Bifurcation lesions represent 10%-15% of interventions and their treatment is associated with a lower success rate and higher complication rate.5 Only selected lesions with involvement of a large side branch (SB) will require the upfront use of a 2-stent approach.1 SB intervention is recommended when the result is considered suboptimal with a flow impairment or presence of significant residual angiographic stenosis associated with ischemic symptoms.1 However, no clear data are available for the routine treatment of residual angiographically significant stenosis in the SB in the absence of ischemic symptoms; the KISS (Keep bifurcation Single Stenting Simple) trial (NCT04285372) aims to answer this question. A poor correlation has been evidenced between the angiographic appearance of a SB stenosis after bifurcation stenting with a provisional stenting technique, and the physiological measures obtained with fractional flow reserve (FFR).6,7 In case of significant residual angiographically significant SB stenosis, a negative FFR has been shown to be associated with a good clinical outcome.8,9
Subsequently, some studies have suggested jailing a pressure wire in the SB before provisional stenting technique in order to directly assess the FFR value after stenting.10,11 However, no data exist on the reliability of the measurements obtained by a jailed FFR pressure wire after being subjected to the mechanical stress of coronary stenting.
The main objective of this study is to evaluate the reliability of the distal pressure to aortic pressure (Pd/Pa) values from a jailed second-generation optical pressure guidewire during bifurcation treatment (the provisional technique). Two identical second-generation optical pressure guidewires were compared. A jailed guidewire (JW) advanced into the SB before stenting and a second free-floating guidewire (FW) introduced into the SB after bifurcation stenting (1 stent implanted and proximal optimization technique [POT] performed). The FW served as the reference standard. The safety objective was the visual assessment of the integrity of the jailed wires using optical electronic microscopy.
Methods
An in vitro bifurcation hydrodynamic model (LifeTec Group) was used (Model 1) (Figure 1) with 3 pressure sensors placed in the main vessel, main branch, and SB (pressure transducer P10-EX [Becton Dickinson] and pressure amplifier [Peekel Picas]). A pressure of 100 mm Hg was set in the hydrodynamic model. Diameters of the bifurcation’s model (plexiglass) proximal main vessel, SB, and main branches were 4.0 mm, 3.0 mm, and 3.0 mm, respectively. For each test, 2 new fiber-optic pressure wires (Optowire, Opsens) were used.
Two configurations were tested, ie, Model 1 without a proximal stenosis and Model 2 with a proximal stenosis (Figure 1). Model 2 was created with the use of a surgical clamp, closed on the first teeth, to evaluate the Pd/Pa measures in a system at lower pressure.
The POT-side-POT technique, with POT performed to reduce stent malapposition in the main vessel, was used as the bifurcation stenting strategy. This technique has been validated as a safe alternative compared with the classic kissing-balloon inflation technique for treating bifurcation lesions.12-15 All procedural steps are illustrated in Figure 2. After equalization, the JW was advanced into the SB and the FW into the main branch. A 3.0 x 22-mm stent was implanted at its nominal pressure over the bifurcation, jailing the JW in the SB. A POT was performed using a noncompliant 4.0 x 12-mm NC Sprinter Rx balloon (Medtronic) at nominal pressure. The FW was then withdrawn and advanced into the SB to the same position as the JW. A 2.5 x 15-mm semicompliant Ryurei balloon (Terumo) was used to open the struts of the jailed SB and a final POT was then performed. Opening of the SB struts was deliberately performed with an undersized balloon and compared with the SB diameter, with the aim of comparing the JW and FW values with a significant but nonocclusive stenosis. At each step of the procedure (before stenting, after stenting, after POT technique, after crossing of the FW into the SB, and during inflation of the 2.5 x 15-mm balloon in the SB), Pd/Pa measurements from the JW and FW were recorded. The JW and FW were retrieved and drift was checked. Optical electrical microscopy of the study wire integrity was performed visually on all wires used (VHX-7000 Series Digital Microscope, Keyence System; Leica Microsystems).
Statistical analysis. It was estimated that 44 measures (22 JW and 22 FW) were necessary to demonstrate noninferiority of the JW compared with the FW using a Pd/Pa margin of 0.02. Sample size calculations were made based on the following assumptions: (1) the definition of signal drift in a pressure guidewire as the deviation of the pressure measured by the guidewire sensor (Pd) higher than 3 mm Hg/h compared with the aortic pressure measured at the ostium of the catheter (Pa); and (2) signal drift of the OptoWire III optical pressure guidewire is less than 1 mm Hg/h as reported by the manufacturer (Opsens).
Twenty-two measures were obtained in each model and measures recorded to assess noninferiority were taken from the steps where FW recrossed in the SB and during SB balloon inflation (JW and FW were located in the same position in the SB, permitting a direct comparison).
Variables were described as number (%) or mean ± standard deviation. Continuous variables were compared using Student’s t test analysis. Correlations were performed using Pearson’s r coefficient correlation. All applicable reported P-values and confidence intervals (CIs) were 2-sided; P<.05 was considered statistically significant. Comparisons were also made using the 1-sample t test and linear regression test. Data analysis was performed with SPSS, version 26.0 (IBM Corporation).
Results
In Model 1 (without proximal stenosis), Pd/Pa measurements of the JW and FW remained similar after stenting and after performing POT (Supplemental Table S1). After recrossing the SB with the FW, Pd/Pa values of the JW and FW remained similar (every comparison had a difference ≤0.01) (Table 1). During balloon inflation in the SB, mean Pd/Pa values of the JW and FW were lower, but similar (0.78 ± 0.13 vs 0.79 ± 0.13, respectively; P=.19).
In Model 2, mean Pd/Pa values after inserting the wires were 0.59 ± 0.01 for the JW and 0.57 ± 0.02 for the FW compared with 0.97 ± 0.01 in both JW and FW in Model 1 without a stenosis (Supplemental Table S2). After recrossing the SB with the FW, mean baseline Pd/Pa values of the JW and FW remained similar (0.51 ± 0.02 vs 0.52 ± 0.02 for the JW and FW, respectively; P=.05) (Table 2). During balloon inflation in the SB, Pd/Pa values of the JW and FW were lower and similar (both 0.24 ± 0.02; P=.68).
A strong correlation was found comparing Pd/Pa values between JW and FW in Model 1 after FW recross (r=0.91) and during SB balloon inflation (r=0.99). A strong correlation was found comparing Pd/Pa values between JW and FW in Model 2 after FW recross (r=0.85) and during balloon inflation (r=0.92). The Pd/Pa difference between the JW and FW (combining all measures recorded after FW recross in the SB and during balloon inflation) remained ≤0.02 in all cases, and in half of cases, the JW and FW registered the same value (Supplemental Figure S1). The difference observed in the 44 pairs was within the prespecified margin of 0.02 for demonstrating noninferiority of the JW compared with FW measurement.
Absolute values of pressures recorded from the JW and SB pressure sensors (Table 3) were comparable and remained similar after stent implantation and POT were performed.
No drift occurred on the JW, all measures were ≤0.01 except for a single value of 0.02. One case of drift (0.04) occurred on a FW (Supplemental Figure S2).
After retrieval, the JW was analyzed using optical electrical microscopy. Visually no major structural damages were observed compared with the FW (Figure 3 and Supplemental Figure S3).
Discussion
The use of a durable fiberoptic pressure guidewire as a JW has been shown safe and clinically useful in guiding SB treatment in bifurcation percutaneous coronary intervention (PCI).11
The main outcome from our study confirms the reliability of Pd/Pa values obtained by a jailed optical pressure guidewire. A strong correlation was observed compared with the FW after recrossing the SB (r=0.91) (Figure 4 and Figure 6). These results remained unchanged during SB balloon inflation when absolute pressure values were lower, mimicking a residual significant stenosis (r=0.99) (Figure 5 and Figure 6).
Model 2, with overall lower absolute pressure, confirms good reliability of the Pd/Pa value from the JW. This adds more strength on the pressure wire in case of SB dissection with limiting flow or severe stenosis to safely rely on the measures recorded.
The similarity of the values from the JW and FW remained constant in a low range of Pd/Pa values (from 0.21 to 0.99) (Table 1 and Table 2). Considering the 44 comparisons made, in 55% of the measures FW and JW recorded the same value and a 0.01 difference was recorded in 41% of measures. A 0.02 difference was measured in 4% of cases (Supplemental Figure S1).
FFR provides an important functional metric of a SB stenosis after bifurcation PCI, even in the presence of a residual angiographically severe stenosis.2,3 Prior data show that after bifurcation PCI, FFR evaluation of SBs with angiographically significant residual stenosis (>75%), only 20 of 73 lesions were found functionally significant (FFR <0.75).16 As a partial mechanistic explanation, the analysis of coronary computed tomography angiography revealed that a typical SB supplies less myocardium than the main branch, therefore leading to higher FFR values in general.1,17,18 A negative FFR in the SB, obtained from a jailed pressure wire, even in the presence of a visual significant stenosis, could limit unnecessary SB intervention. The risk of dissection during rewiring or SB balloon angioplasty, with the resulting need for additional stenting, could be lowered. However, our strategy would not be useful in cases of bifurcation treatment with systematic SB opening with/without kissing-balloon technique performed, as the SB would be rewired in any case.
A low rate of drift was found in our study (2.2%), similar to a prior study (4.1%) of an earlier generation of Opsens fiberoptic pressure guidewire.11 The low rate of drift found appears related to the nature of the pressure wire, with a lower rate of drift of the optical pressure wires compared with the piezoelectric pressure wires.19,20
We successfully retrieved all of the JWs without any interference of the concave pressure sensor window. In a slightly different configuration of the in vitro model, with ostial stenting, Optowire mechanical pullback through proximal stent struts in the main branch caused mechanical resistance without strut traction in over 50% of cases.21 In our in vitro analysis, we did not notice such interference. Furthermore, a prior in vivo analysis did not find such interference during 51 FFR measurements.11 We evaluated all of the JWs and FWs using optical electronic microscopy to evaluate possible structural damage. No wire fractures were observed and no structural damage was seen close to the pressure sensor casing, especially on the JW (Supplemental Figure S3).
Study limitations. Our study has several limitations. The bifurcation plexiglass model may not fully represent a true coronary bifurcation lesion with atherosclerotic plaque, where the retrieval of JWs can encounter more resistance due to lesion morphology and calcium. Because nominal pressures for the stent implantation and noncompliant balloon inflation (POT and re-POT) were used, we cannot exclude a different structural interaction at higher pressure values; however, higher pressure values (median, 20 atm) were used in a prior study without macroscopic structural damages identified.11 Our bifurcation strategy treatment was the POT-side-POT technique, and our results cannot be applied to the kissing-balloon technique. Last, our results cannot be applied in cases that utilize other pressure guidewires.
Conclusion
In our in vitro bifurcation model, the Pd/Pa value of a second-generation optical pressure guidewire jailed in the SB, during provisional stenting technique, is reliable compared with an FW inserted after stent implantation and POT. In clinical practice, this can reduce the need for unnecessary SB intervention in the absence of ischemia confirmed by physiological measure.
Acknowledgments. We would like to thank Sebastien Lalancette and Michele La Rosa from Opsens for their contribution in the planning and realization of this experiment.
Affiliations and Disclosures
From the 1Department of Cardiology, Lausanne University-Hospital, Lausanne, Switzerland; 2Division of Cardiology Department of Medicine, Weatherhead PET Center, McGovern Medical School at UTHealth and Memorial Hermann Hospital, Houston, Texas; 3Department of Biomedical Engineering, Eindhoven University of Technology, The Netherlands; 4Department of Cardiology, Institut Arnault-Tzanck, Saint Laurent du Var, France; and the 5Department of Cardiology, Cardiovascular Center Aalst OLV Hospital, Aalst, Belgium.
Funding: Opsens provided the financial support to perform the experiment.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Rubimbura reports grants from Terumo, outside the submitted work. Dr Johnson reports unrelated institutional grants from St Jude Medical (CONTRAST) and Philips Volcano (DEFINE-FLOW), as well as Boston Scientific (licensing for smart minimum FFR) outside the submitted work; in addition, Dr Johnson has patents pending to his employer UTHealth on the quantification of aortic valve severity and correction of phasic pressure from fluid-filled catheters. Dr De Bruyne reports grants from Abbott, Boston Scientific, and Biotronik, others from Opsens, Boston Scientific, Abbott, outside the submitted work. Dr Fournier reports personal fees from Cathworks and Bayer, outside the submitted work. Dr Muller reports personal fees from Abbott and Edwards Lifescience, outside the submitted work. The remaining authors report no conflicts of interest regarding the content herein.
Manuscript accepted October 31, 2021.
Address for correspondence: Vladimir Rubimbura, MD, Cardiology Department, Lausanne University-Hospital, Rue du Bugnon 46, 1011 Lausanne, Switzerland. Email: vladimir.rubimbura@chuv.ch
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