Programmable photonic circuits.

The growing maturity of integrated photonic technology makes it possible to build increasingly large and complex photonic circuits on the surface of a chip. Today, most of these circuits are designed for a specific application, but the increase in complexity has introduced a generation of photonic circuits that can be programmed using software for a wide variety of functions through a mesh of on-chip waveguides, tunable beam couplers and optical phase shifters. Here we discuss the state of this emerging technology, including recent developments in photonic building blocks and circuit architectures, as well as electronic control and programming strategies. We cover possible applications in linear matrix operations, quantum information processing and microwave photonics, and examine how these generic chips can accelerate the development of future photonic circuits by providing a higher-level platform for prototyping novel optical functionalities without the need for custom chip fabrication.

Efficacy and Safety of Endovascular Fenestrated and Branched Grafts Versus Open Surgery in Thoracoabdominal Aortic Aneurysm Repair: An Updated Systematic Review, Meta-analysis, and Meta-regression.

OBJECTIVE: To provide an updated systematic review and meta-analysis with meta-regression of efficacy and safety of fenestrated/branched endovascular repair of thoracoabdominal aortic aneurysms (TAAAs) compared with open repair. BACKGROUND: Endovascular repair of TAAAs may be a promising alternative to open surgery by reducing invasiveness and expanding the eligible population, but evidence remains limited. METHODS: We applied "Prepared Items for Systematic Reviews and Meta-analysis" guidelines to retrieve, quantitatively pool, and critically evaluate the efficacy and safety (including 30-day mortality, reintervention, spinal cord injury [SCI], and renal injury) of both approaches. Original studies were retrieved from PubMed, Embase, and Cochrane Library until April 20, 2022, excluding papers reporting <10 patients. Pooled proportions and means were determined using a random-effect model. Heterogeneity between studies was evaluated with I2 statistics. RESULTS: Sixty-four studies met the predefined inclusion criteria. Endovascular cohort patients were older and had higher rates of comorbidities. Endovascular repair was associated with similar proportions of mortality (0.07, 95% confidence intervals [CI]: 0.06-0.08) compared with open repair (0.09, 95% CI: 0.08-0.12; P = 0.22), higher proportions of reintervention (0.19, 95% CI: 0.13-0.26 vs 0.06, 95% CI: 0.04-0.10; P < 0.01), similar proportions of transient SCI (0.07, 95% CI: 0.05-0.09 vs 0.06, 95% CI: 0.05-0.08; P = 0.28), lower proportions of permanent SCI (0.04, 95% CI: 0.03-0.05 vs 0.06, 95% CI: 0.05-0.07; P < 0.01), and renal injury (0.08, 95% CI: 0.06-0.10 vs 0.13, 95% CI: 0.09-0.17; P = 0.02). Results were affected by high heterogeneity and potential publication bias. CONCLUSIONS: Despite these limitations and the lack of randomized trials, this meta-analysis suggests that endovascular TAAA repair could be a safer alternative to the open approach.

In-hospital cost-effectiveness analysis of open versus staged fenestrated/branched endovascular elective repair of thoracoabdominal aneurysms.

OBJECTIVE: To compare costs and effectiveness of elective open (OR) vs fenestrated/branched endovascular (ER) repair of thoracoabdominal aneurysms (TAAAs) in a high-volume center. METHODS: This single-center retrospective observational study (PRO-ENDO TAAA Study, NCT05266781) was designed as part of a larger health technology assessment analysis. All electively treated TAAAs between 2013 and 2021 were analyzed and propensity-matched. End points were clinical success, major adverse events (MAEs), hospital direct costs, and freedom from all causes and aneurysm-related mortality and reinterventions. Risk factors and outcomes were homogeneously classified according to the Society of Vascular Surgery reporting standards. Cost-effectiveness value and incremental cost-effectiveness ratio were calculated, considering the absence of MAEs as a measure of effectiveness. RESULTS: Propensity matching identified 102 pairs of patients out of 789 TAAAs. Mortality, MAE, permanent spinal cord ischemia rates, respiratory complications, cardiac complications, and renal injury were higher for OR (13% vs 5%, P = .048; 60% vs 17%, P < .001; 10% vs 3%, P = .045; 91% vs 18%, P < .001; 16% vs 6%, P = .024; 27% vs 6%, P < .001, respectively). Access complication rate (6% vs 27%; P < .001) was higher in the ER group. Intensive care unit stay was longer (P < .001) for OR, and ER patients were discharged home more frequently (3% vs 94%; P < .001). No differences in midterm end points were observed at 2 years. Despite ER reducing all the hospital cost items (-42% to -88%, P < .001), the higher expenses (P < .001) of the endovascular devices increased the overall cost of ER by 80%. Cost-effectiveness value for ER was favorable to OR (56,365 vs 64,903 €/patient) with an incremental cost-effectiveness ratio of 48,409 € per MAE saved. CONCLUSIONS: ER of TAAA reduces perioperative mortality and morbidity compared with OR, with no differences in reinterventions and survival rates at midterm follow-up. Despite the expenses for endovascular grafts, ER was found to be more cost-effective in preventing MAEs.

Variable optical true-time delay line breaking bandwidth-delay constraints.

Continuously variable true-time optical delay lines are typically subject to a constraint of the bandwidth-delay product, limiting their use in several applications. In this Letter, we propose an integrated topology that breaks the bandwidth-delay product limit. The device is based on multiple Mach-Zehnder Interferometers (MZIs) arranged in parallel, providing easier control and a larger bandwidth compared to ring resonator-based solutions. The functionality of this architecture is demonstrated with a 4-stage delay line by performing measurements in both the time and frequency domains. The delay line introduces a delay of 90 ps over a bandwidth of more than 22 GHz with a negligible group delay distortion, operates on a wavelength range of about 60 nm, and is scalable to a higher number of MZI stages.

An International Expert-Based CONsensus on Indications and Techniques for aoRtic balloOn occLusion in the Management of Ruptured Abdominal Aortic Aneurysms (CONTROL-RAAA).

OBJECTIVE: To report on the recommendations of an expert-based consensus on the indications, timing, and techniques of aortic balloon occlusion (ABO) in the management of ruptured abdominal aortic aneurysms (rAAA). METHODS: Eleven facilitators created appropriate statements regarding the study issues that were voted on using a 4-point Likert scale with open-comment fields, by a selected panel of international experts (vascular surgeons and interventional radiologists) using a 3-round modified Delphi consensus procedure (study period: January-April 2023). Based on the experts' responses, only the statements reaching grade A (full agreement ≥75%) or B (overall agreement ≥80% and full disagreement <5%) were included in the final study report. The consistency of each round's answers was also graded using Cohen's kappa, the intraclass correlation coefficient, and, in case of double resubmission, Fleiss kappa. RESULTS: Sixty-three experts were included in the final analysis and voted on 25 statements related to indication and timing (n=6), and techniques (n=19) of ABO in the setting of rAAA. Femoral sheath or ABO should be preferably placed in the operating room, via a percutaneous transfemoral access, on a stiff wire (grade B, consistency I), ABO placement should be suprarenal and last less than 30 minutes (grade B, consistency II), postoperative peripheral vascular status (grade A, consistency II) and laboratory testing every 6 to 12 hours (grade B, consistency) should be assessed to detect complications. Formal training for ABO should be implemented (grade B, consistency I). Most of the statements in this international expert-based Delphi consensus study might guide current choices for indications, timing, and techniques of ABO in the management of rAAA. Clinical practice guidelines should incorporate dedicated statements that can guide clinicians in decision-making. CONCLUSIONS: At arrival and during both open or endovascular procedures for rAAA, selective use of intra-aortic balloon occlusion is recommended, and it should be performed preferably by the treating physician in aortic pathology. CLINICAL IMPACT: This is the first consensus study of international vascular experts aimed at defining the indications, timing, and techniques of optimal use of ABO in the clinical setting of rAAA. Aortic occlusion by endovascular means (or ABO) is a quick procedure in properly trained hands that may play an important role as a temporizing measure until the definitive aortic repair is achieved, whether by endovascular or open means. Since data on its use in hemodynamically unstable patients are limited in the literature, owing to practical challenges in the performance of well-conducted prospective studies, understanding real-world use by experts is of importance in addressing critical issues and identifying main gaps in knowledge.

Outcomes of Percutaneous Access to the First Versus Third Segment of Axillary Artery During Aortic Procedures.

PURPOSE: This article aims at investigating the outcomes of percutaneous access via the first versus third axillary artery (AXA) segments with closure devices during aortic procedures. MATERIALS AND METHODS: All patients receiving percutaneous AXA access closed with Perclose ProGlide device (Abbott, Santa Clara, California) from 2008 to 2021 were included in a retrospective multicenter registry (NCT: 04589962). Efficacy endpoint was the technically successful percutaneous procedure (no open conversion). Safety endpoints were stroke and access complications according to the Valve Academic Research Consortium-3 reporting standards. The first (AXA1) or third (AXA3) axillary puncture sites were compared. RESULTS: A total of 412 percutaneous AXA accesses were included: 172 (42%) in AXA1 and 240 (58%) in AXA3. Left AXA was catheterized in 363 cases (76% of AXA1 vs 97% of AXA3, p<0.001) and 91% of fenestrated/branched endovascular repair (F/BEVAR) procedures were conducted from the left. A ≥12F internal diameter (ID) sheath was used in 49% of procedures. Open conversion rate was 1%, no major vascular complications occurred, and only one major non-vascular complication was recorded. Primary closure failure occurred in 18 AXA1 (11%) and 32 AXA3 accesses (13%), treated by covered (8.3%) or bare-metal (2.7%) stenting. Bailout stent patency was 100% at median follow-up of 12 months, with 6 of 6 stents still patent after >36 months of follow-up. Stroke rate was 4.4%. An introducer sheath >12F was independently associated with both access complications (p<0.001) and stroke (p=0.005), while a right-side access was associated with stroke only (p=0.034). Even after adjustment for covariates, AXA1 versus AXA3 showed an equal success rate (odds ratio [OR]=0.537, 95% confidence interval [CI]=0.011-1.22 for AXA3, p=0.104). The combination of AXA3 and a >10F introducer sheath provided worse outcomes compared with >10F sheaths through AXA1 (OR for success=0.367, 95% CI=0.176-0.767, p=0.008). This was not confirmed for >12F sheaths, associated with similar outcomes (p=0.31 AXA 1 vs AXA 3). CONCLUSION: Major local complications with the percutaneous axillary approach and ≤12F sheaths are infrequent and solvable by complementary endovascular interventions. Stroke risk remains an issue. First and third AXA segments are both amenable for access with good results, but larger sheaths (12F) perform better in AXA1. CLINICAL IMPACT: Percutaneous access with vascular closure devices at the first or third axillary artery (AXA) segments during aortic procedures is burdened by a negligible risk of open conversion. Local complications with the percutaneous axillary approach are infrequent and solvable by complementary endovascular interventions. First and third AXA segments are both amenable to access with excellent results, but larger sheaths (12F) perform better in the wider first AXA segment. In this setting, bailout stenting does not appear to be associated with mid-term stent occlusion.

Spinal Cord Ischemia After Thoracoabdominal Aortic Aneurysms Endovascular Repair: From the Italian Multicenter Fenestrated/Branched Endovascular Aneurysm Repair Registry.

PURPOSE: The aim of this study is to report an Italian multicenter experience analyzing the incidence and the risk factors associated with spinal cord ischemia (SCI) in a large cohort of thoracoabdominal aortic aneurysms (TAAAs) treated by fenestrated-branched endovascular aneurysm repair (F-/B-EVAR). MATERIALS AND METHODS: All consecutive patients undergoing F-/B-EVAR in 4 Italian university centers between 2008 and 2019 were prospectively recorded and retrospectively analyzed. Spinal cord ischemia, 30 day/in-hospital adverse events, and mortality were assessed as early outcomes. Risk factors for SCI were determined by multivariable analysis. RESULTS: A total of 351 patients received F-/B-EVAR for a TAAA. Twenty-eight (8.0%) patients died within 30 postoperative days or during the hospitalization. Regarding SCI, 47 patients (13.4%) developed neurological symptoms related to spinal cord impaired perfusion. Among them, 17 (4.8%) had a major permanent impairment. The multivariable analysis identified that SCI was associated with Crawford extent I to III (odds ratio [OR]: 20.90, p=0.004, 95% confidence interval [CI]=2.69-162.57), and with endovascular procedures performed for ruptured TAAA (OR: 5.74, p=0.010, 95% CI=1.53-21.57). Spinal cord ischemia was also significantly associated with a grade 3 bleeding during the visceral stage (OR: 4.34, p=0.005, 95% CI=1.55-12.16) and a grade 2 renal insufficiency at 30 days (OR: 7.45, p=0.002, 95% CI=2.12-26.18). CONCLUSION: The present study indicates that SCI is still an open issue after extent I to III TAAA endovascular repair, while its incidence in extent IV TAAA and pararenal/juxtarenal aneurysms is rare. Thoracoabdominal aortic aneurysms extension, urgent TAAA repair for rupture, severe bleeding, and 30 day renal insufficiency have been identified as significant risk factors for SCI. In the presence of such factors, adjunctive strategies may be considered to reduce SCI rates, while in low-risk patients invasive or potentially-risky maneuvers might not be justified.

Multicentre International Registry of Open Surgical Versus Percutaneous Upper Extremity Access During Endovascular Aortic Procedures.

OBJECTIVE: To investigate access failure (AF) and stroke rates of aortic procedures performed with upper extremity access (UEA), and compare results of open surgical vs. percutaneous UEA techniques with closure devices. METHODS: A physician initiated, multicentre, ambispective, observational registry (SUPERAXA - NCT04589962) was carried out of patients undergoing aortic procedures requiring UEA, including transcatheter aortic valve replacement, aortic arch, and thoraco-abdominal aortic endovascular repair, pararenal parallel grafts, renovisceral and iliac vessel repair. Only vascular procedures performed with an open surgical or percutaneous (with a suture mediated vessel closure device) UEA were analysed. Risk factors and endpoints were classified according to the Society for Vascular Surgery and VARC-3 (Valve Academic Research Consortium) reporting standards. A logistic regression model was used to identify AF and stroke risk predictors, and propensity matching was employed to compare the UEA closure techniques. RESULTS: Sixteen centres registered 1 098 patients (806 men [73.4%]; median age 74 years, interquartile range 69 - 79 years) undergoing vascular procedures using open surgical (76%) or percutaneous (24%) UEA. Overall AF and stroke rates were 6.8% and 3.0%, respectively. Independent predictors of AF by multivariable analysis included pacemaker ipsilateral to the access (odds ratio [OR] 3.8, 95% confidence interval [CI] 1.2 - 12.1; p = .026), branched and fenestrated procedure (OR 3.4, 95% CI 1.2 - 9.6; p = .019) and introducer internal diameter ≥ 14 F (OR 6.6, 95% CI 2.1 - 20.7; p = .001). Stroke was associated with female sex (OR 3.4, 95% CI 1.3 - 9.0; p = .013), vessel diameter > 7 mm (OR 3.9, 95% CI 1.1 - 13.8; p = .037), and aortic arch procedure (OR 7.3, 95% CI 1.7 - 31.1; p = .007). After 1:1 propensity matching, there was no difference between open surgical and percutaneous cohorts. However, a statistically significantly higher number of adjunctive endovascular procedures was recorded in the percutaneous cohort (p < .001). CONCLUSION: AF and stroke rates during complex aortic procedures employing UEA are non-negligible. Therefore, selective use of UEA is warranted. Percutaneous access with vessel closure devices is associated with similar complication rates, but more adjunctive endovascular procedures are required to avoid surgical exposure.

Temperature and wavelength drift tolerant WDM transmission and routing in on-chip silicon photonic interconnects.

We demonstrate a temperature and wavelength shift resilient silicon transmission and routing interconnect system suitable for multi-socket interconnects, utilizing a dual-strategy CLIPP feedback circuitry that safeguards the operating point of the constituent photonic building blocks along the entire on-chip transmission-multiplexing-routing chain. The control circuit leverages a novel control power-independent and calibration-free locking strategy that exploits the 2nd derivative of ring resonator modulators (RMs) transfer function to lock them close to the point of minimum transmission penalty. The system performance was evaluated on an integrated Silicon Photonics 2-socket demonstrator, enforcing control over a chain of RM-MUX-AWGR resonant structures and stressed against thermal and wavelength shift perturbations. The thermal and wavelength stress tests ranged from 27°C to 36°C and 1309.90 nm to 1310.85 nm and revealed average eye diagrams Q-factor values of 5.8 and 5.9 respectively, validating the system robustness to unstable environments and fabrication variations.

Early and mid-term outcomes of open popliteal artery aneurysm repair with prosthetic grafts.

OBJECTIVE: The aim of the present study was to assess the early and mid-term outcomes of open surgical repair (OSR) for popliteal artery aneurysms (PAAs) with prosthetic grafts. METHODS: The pre-, intra-, and postoperative data for all the patients who had undergone OSR for PAAs with prosthetic grafts at our Institution between January 2009 and July 2019 were included in a prospectively maintained database, which was retrospectively analyzed. Primary patency was defined as uninterrupted flow (<50% stenosis) in the graft with no additional procedures performed. Secondary patency was defined as the restoration of graft patency. RESULTS: A total of 82 patients had undergone OSR for 104 PAAs (median age, 71 years; interquartile range [IQR], 67-78 years; 82 men) with prosthetic grafts. Of the 104 PAAs, 72 (68%) had been asymptomatic. The median diameter was 30 mm (IQR, 24-37 mm). A medial approach was used for 35 PAAs (34%) and a posterior approach for 69 (65%). The repairs consisted of aneurysmectomy or aneurysm ligation without removal with an interposition graft placed and end-to-end anastomoses. The median operative time was 120 minutes (IQR, 103-142 minutes). The estimated blood loss was 281 mL (IQR, 150-281 mL). Only one patient treated with a posterior approach sustained a permanent peroneal nerve lesion. A second patient also treated via the posterior approach had required surgical revision for bleeding on postoperative day 2. No temporary lesions were recorded. No early amputations were required, and no perioperative deaths occurred. The median length of stay was 3 days (IQR, 3-4 days). An expanded polytetrafluoroethylene graft was used in 92 cases (88%) and a Dacron graft in 12 cases (12%). An 8-mm graft was used in 64 cases (62%). The median follow-up was 34.6 months (IQR, 8.5-62.7 months). No related mortality occurred. Of the 104 PAAs, 19 had required reintervention, with primary and secondary patency of 78% and 88% at 3 years, respectively. The median interval to reintervention was 28.3 months. CONCLUSIONS: OSR of PAAs with prosthetic grafts is safe and feasible, with good mid-term results and satisfactory primary and secondary patency at 3 years.

Fenestrated-branched endovascular repair for distal thoracoabdominal aortic pathology after total aortic arch replacement with frozen elephant trunk.

OBJECTIVE: To report the outcomes of fenestrated-branched endovascular repair (FBEVAR) for thoracoabdominal aortic pathology after total aortic arch replacement with frozen elephant trunk (TAR+FET). METHODS: Interrogation of prospectively maintained databases from four high-volume aortic centers identified consecutive patients treated with distal FBEVAR after prior TAR+FET between August 2013 and September 2020. The primary end point was 30-day/in-hospital mortality. Secondary end points were technical success, early clinical success, midterm survival, and freedom from reintervention. Data are presented as median (interquartile range). RESULTS: A total of 39 patients (21 men; median age, 73 years [67-75 years]) with degenerative (n = 22) and postdissection thoracoabdominal aortic aneurysms (n = 17) (median diameter, 71 mm [61-78 mm]) were identified. Distal FBEVAR was intended in 27 patients (median interval, 9.8 months [6.2-16.6 months]), anticipated in 7, and unexpected in 5. A total of 31 patients had a two- (n = 24) or three-stage (n = 7) distal FBEVAR. Renovisceral target vessel preservation was 99.3% (145 of 146). Early primary and secondary technical success was 92% and 97%, respectively. Thirty-day mortality was 2.6% (n = 1; respiratory failure and spinal cord ischemia [SCI]). Six survivors also developed SCI, which was associated with complete (n = 4) or partial recovery (n = 2) at hospital discharge. No patients required renal replacement therapy or suffered a stroke. Early clinical success was 95%. Median follow-up was 30.5 months (23.7-49.7 months). Eleven patients required 16 late reinterventions. Estimated 3-year survival and freedom from reintervention were 84% ± 6% and 63% ± 10%, respectively. CONCLUSIONS: Distal FBEVAR after prior TAR+FET is associated with high technical success and low early mortality. The risk of SCI is significant although the majority of patients demonstrate full or partial recovery before hospital discharge. Midterm patient survival is favorable, but there remains a high requirement for late reintervention. FBEVAR represents an acceptable alternative to distal open thoracoabdominal aortic aneurysm repair.

High-sensitivity transparent photoconductors in voltage-controlled silicon waveguides.

On-chip optical power monitors are essential elements to calibrate, stabilize, and reconfigure photonic integrated circuits. Many applications require in-line waveguide detectors, where a trade-off has to be found between large sensitivity and high transparency to the guided light. In this work, we demonstrate a transparent photoconductor integrated on standard low-doped silicon-on-insulator waveguides that reaches a photoconductive gain of more than 106 and an in-line sensitivity as high as -60 dBm. This performance is achieved by compensating the effect of electric charges in the cladding oxide through a bias voltage applied to the chip substrate or locally through a gate electrode on top of the waveguide, allowing one to tune on demand the conductivity of the core to the optimum level.

Amorphous-silicon visible-light detector integrated on silicon nitride waveguides.

Visible-light integrated photonics is emerging as a promising technology for the realization of optical devices for applications in sensing, quantum information and communications, imaging, and displays. Among the existing photonic platforms, high-index-contrast silicon nitride (Si3N4) waveguides offer broadband transparency in the visible spectral range and a high scale of integration. As the complexity of photonic integrated circuits (PICs) increases, on-chip detectors are required to monitor their working point for reconfiguration and stabilization operations. In this Letter, we present a semi-transparent in-line power monitor integrated on Si3N4 waveguides that operates in the red-light wavelength range (660 nm). The proposed device exploits the photoconductivity of a hydrogenated amorphous-silicon (a-Si:H) film that is evanescently coupled to an optical waveguide. Experimental results show a responsivity of 30 mA/W, a sensitivity of -45 dBm, and a sub-µs time response. These features enable the use of the proposed photoconductor for high-sensitivity monitoring and control of visible-light Si3N4 PICs.

Active Opto-Magnetic Biosensing with Silicon Microring Resonators.

Integrated optical biosensors are gaining increasing attention for their exploitation in lab-on-chip platforms. The standard detection method is based on the measurement of the shift of some optical quantity induced by the immobilization of target molecules at the surface of an integrated optical element upon biomolecular recognition. However, this requires the acquisition of said quantity over the whole hybridization process, which can take hours, during which any external perturbation (e.g., temperature and mechanical instability) can seriously affect the measurement and contribute to a sizeable percentage of invalid tests. Here, we present a different assay concept, named Opto-Magnetic biosensing, allowing us to optically measure off-line (i.e., post hybridization) tiny variations of the effective refractive index seen by microring resonators upon immobilization of magnetic nanoparticles labelling target molecules. Bound magnetic nanoparticles are driven in oscillation by an external AC magnetic field and the corresponding modulation of the microring transfer function, due to the effective refractive index dependence on the position of the particles above the ring, is recorded using a lock-in technique. For a model system of DNA biomolecular recognition we reached a lowest detected concentration on the order of 10 pm, and data analysis shows an expected effective refractive index variation limit of detection of 7.5×10-9 RIU, in a measurement time of just a few seconds.

Outcomes of routine use of percutaneous access with large-bore introducer sheaths (>21F outer diameter) during endovascular aneurysm repair.

OBJECTIVE: The objective of this study was to evaluate the performance of percutaneous femoral access with large-bore sheaths (>21F outer diameter) mainly employed for thoracic and thoracoabdominal aortic endovascular treatment and to stratify the outcomes on the basis of the introducer size. METHODS: Between December 2015 and December 2018, all consecutive patients who received endovascular repair through a percutaneous approach with a suture-mediated vascular closure device (VCD) and the preclose technique were included in a retrospective single-center study called Totally Percutaneous Approach to Endovascular Treatment of Aortic Aneurysms (PEVAR-PRO). The morphologic characteristics of the access vessels and patients' demographics were recorded, and 30-day closure success was defined as the primary end point. Analysis of the closure success comparing large-bore sheaths vs small-bore sheaths (≤21F outer diameter) was performed after 1:1 propensity score matching of preoperative confounding variables. RESULTS: The closure success rate of the entire study cohort was 94% (622 femoral accesses in 360 patients; median age, 74 years; 84% male). Univariate analysis identified eight different factors associated with failure, but only two remained significant on multivariate analysis: diabetes (odds ratio [OR], 2.8; 95% confidence interval [CI], 1.3-6.2; P = .011) and common femoral artery stenosis >50% (OR, 4.5; 95% CI, 1.3-13.7; P = .019). After propensity score matching (1:1, 172 femoral accesses per group), closure success rate was not significantly different between large-bore and small-bore sheaths (90.7% vs 93.0%; P = .43). Multivariate analysis of the large-sheath group identified two factors associated with failure: small (<9 mm) femoral arteries (OR, 6.9; 95% CI, 1.5-31.6; P = .13) and access vessel calcifications involving more than one-third of the circumference (OR, 7.9; 95% CI, 2.1-29.4; P = .002). Neither previous femoral cutdown (44 accesses [23%]) nor percutaneous closure with VCDs (38 accesses [20%]) affected the closure success rate in the large-sheath group. Closure failure did not significantly increase the need for postoperative blood transfusions or hospital length of stay. CONCLUSIONS: Off-label use of VCDs and the preclose technique for percutaneous approach with large-bore sheaths needed for complex aortic endovascular procedures is safe and feasible. Closure success rate is not significantly different from that obtained with on-label application of VCDs with smaller sheaths.

Dynamic mitigation of nonlinear effects in a silicon photonic add-drop filter.

Nonlinear effects limit the maximum amount of optical power that can be handled by silicon photonic integrated circuits (PICs). This limitation is particularly tight in resonant devices such as microring resonator (MRR) filters, suffering from a power-dependent resonance spread due to intracavity power enhancement. In this Letter, we present an automatic control system that can dynamically mitigate the nonlinear spectral distortion of silicon MRR filters by thermally controlling each MRR. The benefit of the proposed scheme is demonstrated on the spectral response of a polarization-transparent coupled-MRR filter operating on a 200 Gbit/s signal. The proposed technique, which does not require a priori information on the PIC topology and functionality, is scalable to more complex architectures and can be employed to compensate for generic nonlinear effects in different photonic platforms.

Electrical conductance of silicon photonic waveguides.

Many optoelectronic devices embedded in a silicon photonic chip, like photodetectors, modulators, and attenuators, rely on waveguide doping for their operation. However, the doping level of a waveguide is not always reflecting in an equal amount of free carriers available for conduction because of the charges and trap energy states inevitably present at the Si/SiO2 interface. In a silicon-on-insulator technology with 1015cm-3p-doped native waveguides, this can lead to a complete depletion of the core from free carriers and to a consequently very high electrical resistance. This Letter experimentally quantifies this effect and shows how the amount of free carriers in a waveguide can be modified and restored to the original doping value with a proper control of the chip substrate potential. A similar capability is also demonstrated by means of a specific metal gate integrated above the waveguide that allows fine control of the conductance with high locality level. This paper highlights the linearity achievable in the conductance modulation that can be exploited in a number of possible applications.

Endovascular embolization of a lower limb arteriovenous fistula using a vascular plug deployed with a through-and-through arteriovenous access.

A 66-year-old man was referred to our institution for a popliteal arteriovenous fistula (AVF). The patient presented with left lower limb edema associated with a pulsatile popliteal mass with bruit at auscultation, and no sign of lower limb ischemia. Relevant history included penetrating stabbing wound to that leg 50 years prior. A computed tomography scan demonstrated an AVF with a tract 10 mm in length and 6 mm in diameter at the level of the popliteal fossa. An AMPLATZER Vascular Plug III 12 mm (AVP - AGA Medical Corporation, Minneapolis, MN) was initially deployed through a percutaneous femoral arterial access. Initial angiographic check showed inadequate sealing, so the plug was repositioned from the venous side of the AVF with a through-and-through arteriovenous access from the posterior tibial vein, achieving a correct sealing. At 24-month follow-up the patient does not present any complications from the procedure, and the AVF remains occluded.

Thoracic Endovascular Aortic Repair With Additional Distal Bare Stents in Type B Aortic Dissection Does Not Prevent Long-Term Aneurysmal Degeneration.

PURPOSE: TEVAR (thoracic endovascular aortic repair) + PETTICOAT (Provisional ExTension to Induce COmplete ATtachment) technique has been selectively employed since 2005 at our institution during endovascular treatment of type B aortic dissection (TBD). The aim of this study is to evaluate the long-term (>5 years) clinical results and the evolution of aortic volume. MATERIALS AND METHODS: All the patients receiving an endovascular treatment for TBD with the PETTICOAT technique were collected in a prospectively maintained database and follow-up computed tomography scan were retrospectively analyzed. Study endpoints included short- and long-term clinical success (absence of need for reintervention) and any major adverse event. The volumes of thoracic and abdominal aorta at long-term follow-up were also analyzed. RESULTS: Twenty-eight patients received a TEVAR + PETTICOAT and were followed up (median follow-up 85 months). Primary 30-day clinical success rate was 82% with an adverse event rate of 31%; 4 type I endoleak and 1 retrograde dissection were recorded. Secondary mid-term clinical success was 96% while the long-term clinical success rate was 79%. Six cases (21%) received either an open repair or an endovascular repair for a significant distal aortic enlargement at follow-up. With regards to volumetric analysis, an increase of overall (thoracic and abdominal) aortic volume was observed in 8 cases mainly related to an increase (mean: +31%) of the abdominal volume that was observed in 11 cases. CONCLUSIONS: PETTICOAT technique does not protect from long-term significant aneurysmal degeneration that may require aortic open or endovascular reinterventions. Aortic growth occurs mainly in the bare-stented aorta and thus, life-long surveillance is advisable in these patients.

Vascular Surgery During COVID-19 Emergency in Hub Hospitals of Lombardy: Experience on 305 Patients.

OBJECTIVE: During the most aggressive phase of the COVID-19 outbreak in Italy, the Regional Authority of Lombardy identified a number of hospitals, named Hubs, chosen to serve the whole region for highly specialised cases, including vascular surgery. This study reports the experience of the four Hubs for Vascular Surgery in Lombardy and provides a comparison of in hospital mortality and major adverse events (MAEs) according to COVID-19 testing. METHODS: Data from all patients who were referred to the Vascular Surgery Department of Hubs from 9 March to 28 April 2020 were collected prospectively and analysed. A positive COVID-19 polymerase chain reaction swab test, or symptoms (fever > 37.5 °C, upper respiratory tract symptoms, chest pain, and contact/travel history) associated with interstitial pneumonia on chest computed tomography scan were considered diagnostic of COVID-19 disease. Patient characteristics, operative variables, and in hospital outcomes were compared according to COVID-19 testing. A multivariable model was used to identify independent predictors of in hospital death and MAEs. RESULTS: Among 305 included patients, 64 (21%) tested positive for COVID-19 (COVID group) and 241 (79%) did not (non-COVID group). COVID patients presented more frequently with acute limb ischaemia than non-COVID patients (64% vs. 23%; p < .001) and had a significantly higher in hospital mortality (25% vs. 6%; p < .001). Clinical success, MAEs, re-interventions, and pulmonary and renal complications were significantly worse in COVID patients. Independent risk factors for in hospital death were COVID (OR 4.1), medical treatment (OR 7.2), and emergency setting (OR 13.6). COVID (OR 3.4), obesity class V (OR 13.5), and emergency setting (OR 4.0) were independent risk factors for development of MAEs. CONCLUSION: During the COVID-19 pandemic in Lombardy, acute limb ischaemia was the most frequent vascular disease requiring surgical treatment. COVID-19 was associated with a fourfold increased risk of death and a threefold increased risk of major adverse events.