Transcatheter Aortic Valve Migration During Vascular Access Closure.

We present a novel complication of transcatheter aortic valve replacement (TAVR) involving prosthetic migration due to entanglement by a standard guidewire during non-large bore vascular access closure, followed by successful bail-out using a second transcatheter prosthesis. To our knowledge, this mechanism of prosthesis migration has not been previously described.

Construction and study of instrument response functions for analysis of the National Ignition Facility (NIF) neutron time-of-flight detectors.

The analysis of the National Ignition Facility (NIF) neutron time-of-flight (nToF) detectors uses a forward-fit routine that depends critically on the instrument response functions (IRFs) of the diagnostics. The details of the IRFs used can have large impacts on measurements such as ion temperature and down-scattered ratio (DSR). Here, we report on the recent steps taken to construct and validate nToF IRFs at the NIF to an increased degree of accuracy, as well as remove the need for fixed DSR baseline offsets. The IRF is treated in two parts: a "core," measured experimentally with an x-ray impulse source, and a "tail" that occurs later in time and has limited experimental data. The tail region is calibrated with the data from indirect drive exploding pusher shots, which have little neutron scattering and are traditionally assumed to have zero DSR. Using analytic modeling estimates, the non-zero DSR for these shots is estimated. The impact of varying IRF tail components on DSR is investigated with a systematic parameter study, and good agreement is found with the non-zero DSR estimates. These approaches will be used to improve the precision and uncertainty of NIF nToF DSR measurements.

Constraining time-dependent ion temperature measurements in inertial confinement fusion (ICF) implosions with an intermediate distance neutron time-of-flight (nToF) detector.

A concept for using an intermediate distance (0.3-3.0 m) neutron time-of-flight (nToF) to provide a constraint on the measurement of the time-dependence of ion temperature in inertial confinement fusion implosions is presented. Simulated nToF signals at different distances are generated and, with a priori knowledge of the burn-averaged quantities and burn history, analyzed to determine requirements for a future detector. Results indicate a signal-to-noise ratio >50 and time resolution <20 ps to constrain the ion temperature gradient to ∼±25% (0.5 keV/100 ps).

The Vacuum Cherenkov Detector (VCD) for γ-ray measurements in inertial confinement fusion experiments.

Inertial confinement fusion experiments at both the National Ignition Facility (NIF) and the Laboratory for Laser Energetics OMEGA laser facility currently utilize Cherenkov detectors, with fused silica as the Cherenkov medium. At the NIF, the Quartz Cherenkov Detectors improve the precision of neutron time-of-flight measurements; and at OMEGA, the Diagnostic for Areal Density provides measurements of capsule shell areal densities. An inherent property of fused silica is the radiator's relatively low energy threshold for Cherenkov photon production (Ethreshold < 1 MeV), making it advantageous over gas-based Cherenkov detectors for experiments requiring low-energy γ detection. The Vacuum Cherenkov Detector (VCD) has been specifically designed for efficient detection of low energy γ's. Its primary use is in implosion experiments, which will study reactions relevant to stellar and big-bang nucleosynthesis, such as T(4He,γ)7Li, 4He(3He,γ)7Be, and 12C(p,γ)13N. The VCD is compatible with LLE's standard Ten-Inch Manipulator diagnostic insertion module. This work will outline the design and characterization of the VCD as well as provide results from recent experiments conducted at the OMEGA laser facility.

Experimental achievement and signatures of ignition at the National Ignition Facility.

An inertial fusion implosion on the National Ignition Facility, conducted on August 8, 2021 (N210808), recently produced more than a megajoule of fusion yield and passed Lawson's criterion for ignition [Phys. Rev. Lett. 129, 075001 (2022)10.1103/PhysRevLett.129.075001]. We describe the experimental improvements that enabled N210808 and present the first experimental measurements from an igniting plasma in the laboratory. Ignition metrics like the product of hot-spot energy and pressure squared, in the absence of self-heating, increased by ∼35%, leading to record values and an enhancement from previous experiments in the hot-spot energy (∼3×), pressure (∼2×), and mass (∼2×). These results are consistent with self-heating dominating other power balance terms. The burn rate increases by an order of magnitude after peak compression, and the hot-spot conditions show clear evidence for burn propagation into the dense fuel surrounding the hot spot. These novel dynamics and thermodynamic properties have never been observed on prior inertial fusion experiments.

Design of an inertial fusion experiment exceeding the Lawson criterion for ignition.

We present the design of the first igniting fusion plasma in the laboratory by Lawson's criterion that produced 1.37 MJ of fusion energy, Hybrid-E experiment N210808 (August 8, 2021) [Phys. Rev. Lett. 129, 075001 (2022)10.1103/PhysRevLett.129.075001]. This design uses the indirect drive inertial confinement fusion approach to heat and compress a central "hot spot" of deuterium-tritium (DT) fuel using a surrounding dense DT fuel piston. Ignition occurs when the heating from absorption of α particles created in the fusion process overcomes the loss mechanisms in the system for a duration of time. This letter describes key design changes which enabled a ∼3-6× increase in an ignition figure of merit (generalized Lawson criterion) [Phys. Plasmas 28, 022704 (2021)1070-664X10.1063/5.0035583, Phys. Plasmas 25, 122704 (2018)1070-664X10.1063/1.5049595]) and an eightfold increase in fusion energy output compared to predecessor experiments. We present simulations of the hot-spot conditions for experiment N210808 that show fundamentally different behavior compared to predecessor experiments and simulated metrics that are consistent with N210808 reaching for the first time in the laboratory "ignition."

Understanding the effects of neutron scattering for neutron-yield-isotropy measurements at the NIF.

Neutron-yield diagnostics at the NIF have been upgraded to include 48 detectors placed around the NIF target chamber to assess the DT-neutron-yield isotropy for inertial confinement fusion experiments. Real-time neutron-activation detectors are used to understand yield asymmetries due to Doppler shifts in the neutron energy attributed to hotspot motion, variations in the fuel and ablator areal densities, and other physics effects. In order to isolate target physics effects, we must understand the contribution due to neutron scattering associated with the different hardware configurations used for each experiment. We present results from several calibration experiments that demonstrate the ability to achieve our goal of 1% or better precision in determining the yield isotropy.

Three-dimensional diagnostics and measurements of inertial confinement fusion plasmas.

Recent inertial confinement fusion measurements have highlighted the importance of 3D asymmetry effects on implosion performance. One prominent example is the bulk drift velocity of the deuterium-tritium plasma undergoing fusion ("hotspot"), vHS. Upgrades to the National Ignition Facility neutron time-of-flight diagnostics now provide vHS to better than 1 part in 104 and enable cross correlations with other measurements. This work presents the impact of vHS on the neutron yield, downscatter ratio, apparent ion temperature, electron temperature, and 2D x-ray emission. The necessary improvements to diagnostic suites to take these measurements are also detailed. The benefits of using cross-diagnostic analysis to test hotspot models and theory are discussed, and cross-shot trends are shown.

Proof-of-concept of a neutron time-of-flight ellipsoidal detector.

The time-resolved measurement of neutrons emitted from nuclear implosions at inertial confinement fusion facilities is used to characterize the fusing plasma. Several significant quantities are routinely measured by neutron time-of-flight (nToF) detectors in these experiments. Current nToF detectors use scintillators as well as solid-state Cherenkov radiators. The latter has an inherently faster time response and can provide a co-registered γ-ray measurement as well as improved precision in the bulk hot-spot velocity. This work discusses a nToF ellipsoidal detector that also utilizes a solid-state Cherenkov radiator. The detector has the potential to achieve a fast instrument response function allowing for characterization of the γ-ray burn history as well as the ability to field the detector closer to the fusion source. Proof-of-concept testing of the nToF ellipsoidal detector has been conducted at the National Ignition Facility using commercial optics. A time-resolved neutron signal has been measured from the diagnostic. Preliminary simulations corroborate the results.

Interpolating individual line-of-sight neutron spectrometer measurements onto the "sky" at the National Ignition Facility (NIF).

Nuclear diagnostics provide measurements of inertial confinement fusion implosions used as metrics of performance for the shot. The interpretation of these measurements for shots with low mode asymmetries requires a way of combining the data to produce a "sky map" where the individual line-of-sight values are used to interpolate to other positions in the sky. These interpolations can provide information regarding the orientation of the low mode asymmetries. We describe the interpolation method, associated uncertainties, and correlations between different metrics, e.g., Tion, down scatter ratio, and hot-spot velocity direction. This work is also related to recently reported studies [H. G. Rinderknecht et al., Phys. Rev. Lett. 124, 145002 (2020) and K. M. Woo et al., Phys. Plasmas 27, 062702 (2020)] of low mode asymmetries. We report an analysis that makes use of a newly commissioned line of sight, a scheme for incorporating multiple neutron spectrum measurement types, and recent work on the sources of implosion asymmetry to provide a more complete picture of implosion performance.

Novel use of the Sentinel cerebral protection device during thrombosed septal occluder explant and Atriclip appendage closure.

BACKGROUND: Our case demonstrates a novel use of the Sentinel™ cerebral protection device (SCPD) for prevention of stroke during removal of a thrombus-adherent atrial septal occluder. CASE PRESENTATION: A 45-year-old male with multiple strokes and ostium secundum atrial septal defect closed ten years prior using an Amplatzer Septal Occluder presented with recurrent neurologic symptoms. Over the ensuing year, serial transesophageal echocardiography revealed persistent and worsening device-adherent thrombus despite trial of different anticoagulants. The device appeared to be mal-deployed, prompting the decision for surgical explant. Given concern for embolization during explant, an SCPD was placed. Excision, pericardial patch repair, and Atriclip appendage closure (AAC) were performed. The device demonstrated incomplete endothelialization and microthrombi. SCPD filtration revealed embolic debris. CONCLUSIONS: We demonstrate the first successful use of an SCPD during surgical excision of a mal-deployed occluder. With its ease of use and safety, SCPD may have utility in surgeries with high cardio-embolic risk.

Optimal choice of multiple line-of-sight measurements determining plasma hotspot velocity at the National Ignition Facility.

The measurement of plasma hotspot velocity provides an important diagnostic of implosion performance for inertial confinement fusion experiments at the National Ignition Facility. The shift of the fusion product neutron mean kinetic energy as measured along multiple line-of-sight time-of-flight spectrometers provides velocity vector components from which the hotspot velocity is inferred. Multiple measurements improve the hotspot velocity inference; however, practical considerations of available space, operational overhead, and instrumentation costs limit the number of possible line-of-sight measurements. We propose a solution to this classical "experiment design" problem that optimizes the precision of the velocity inference for a limited number of measurements.

Caution regarding potential changes in AVR practices during the COVID-19 pandemic.

To improve resource allocation in face of the COVID-19 pandemic, hospitals around the country are restricting the performance of elective surgery to preserve ventilators, operating rooms, ICU beds and protect anesthesiologists. For patients with severe aortic stenosis, efforts to bring treatment to symptomatic patients amid this pandemic might lead to favored use of catheter based management using minimalist techniques that do not require these elements. In this context, some patients with well tested surgical indications for valve replacement may be treated by catheter-based methods. It is important that outcomes for these cases are followed closely both at respective sites and in national registries. As we recover from this pandemic, surgical cases should once again be driven by multi-disciplinary discussion and clinical trial data, and not a mentality of crisis management.

Hemopericardium and Cardiac Tamponade Secondary to Migrated Inferior Vena Cava Filter.

A 73-year-old female presented with cardiogenic shock secondary to hemopericardium and cardiac tamponade. Imaging revealed two fractured legs of an inferior vena cava filter, with one leg within the anterior myocardium of the right ventricle and another penetrating the inferior septum through the middle cardiac vein. Hemopericardium and cardiac tamponade were treated with pericardiocentesis. A multidisciplinary meeting resulted in deferring further action against the embedded fractured legs of the filter with consideration of the patient's age and comorbidities. This case report should alert clinicians to think about hemopericardium as a cause of cardiac tamponade and cardiogenic shock in a patient with a history of an inferior vena cava filter placement.

Myasthenia Gravis Induced by Nivolumab: A Case Report.

Nivolumab is a programmed cell death receptor (PD-1) inhibitor therapy for aggressive cancers; however, it poses a risk of immune-related adverse side effects. We present a 73-year-old male with renal cell carcinoma who developed myasthenia gravis (MG) after being treated with nivolumab, proven by acetylcholine receptor antibodies. Our patient presented with symptoms of fatigue and upper and lower extremity weakness, eventually resulting in respiratory failure as a result of MG. Nivolumab is an emerging therapy for advanced cancers but poses severe immune-related adverse events. Clinicians using PD-1 inhibitors should have a high index of suspicion of autoimmune diseases so that early discontinuation and treatment can be established to limit long-term morbidity and mortality.

Myocardial Ischemia with Cannabinoid Use in an Adolescent.

A 16-year-old male presented to the emergency department with chest pain after smoking a synthetic cannabinoid from a vape pen. He had rising troponin I levels, and his exercise stress echocardiogram showed distal apical and septal hypokinesis that resolved at six-month follow-up. This case report raises concern about cardiac ischemia related to synthetic cannabinoid abuse in the pediatric population in the current era of cannabis legalization.