Long-Term Survival among Octogenarians Undergoing Aortic Valve Replacement with or without Simultaneous Coronary Artery Bypass Grafting: A 22-Year Tertiary Single-Center Experience

BACKGROUND

The impact of concomitant coronary artery bypass grafting (CABG) on aortic valve replacement (AVR) in octogenarians is still debated. We analyzed the characteristics and long-term survival of octogenarians undergoing isolated AVR and AVR + CABG.

METHODS

All octogenarians who consecutively underwent AVR with or without concomitant CABG at our tertiary cardiac center between 2000 and 2022 were included. Patients with redo, emergent, or any other concomitant procedures were excluded. The primary endpoints were 30-day and long-term survival. The secondary endpoints were early postoperative outcomes and determinants of long-term survival. Univariable and multivariable logistic regression analyses were performed to identify independent predictors of 30-day mortality, and Cox regression analysis was performed for predictors of adverse long-term survival.

RESULTS

A total of 1011 patients who underwent AVR (83.0 [81.0-85.0] years, 42.0% males) and 1055 with AVR + CABG (83.0 [81.2-85.4] years, 66.1% males) were included in our study. Survival at 30 days and at 1, 3, and 5 years in the AVR group was 97.9%, 91.5%, 80.5%, and 66.2%, respectively, while in the AVR + CABG group it was 96.2%, 89.6%, 77.7%, and 64.7%, respectively. There was no significant difference in median postoperative survival between the AVR and AVR + CABG groups (7.1 years [IQR: 6.7-7.5] vs. 6.6 years [IQR: 6.3-7.2], respectively, p = 0.21). Significant predictors of adverse long-term survival in the AVR group included age (hazard ratio (HR): 1.09; 95% CI: 1.06-1.12, p < 0.001), previous MI (HR: 2.08; 95% CI: 1.32-3.28, p = 0.002), and chronic kidney disease (HR 2.07; 95% CI: 1.33-3.23, p = 0.001), while in the AVR + CABG group they included age (HR: 1.06; 95% CI: 1.04-1.10, p < 0.001) and diabetes mellitus (HR: 1.48; 95% CI: 1.15-1.89, p = 0.002). Concomitant CABG was not an independent risk factor for adverse long-term survival (HR: 0.89; 95% CI: 0.77-1.02, p = 0.09).

CONCLUSIONS

The long-term survival of octogenarians who underwent AVR or AVR + CABG was similar and was not affected by adding concomitant CABG. However, octogenarians who underwent concomitant CABG with AVR had significantly higher in-hospital mortality. Each decision should be discussed within the heart team.

P-P30 Outcomes from resection of pancreatic metastases and non-neuroendocrine, non-pancreatic tumours

Background

Isolated metastatic disease within the pancreas is an uncommon finding. The potentially higher perioperative risk and low incidence of resectable metastases has limited the development of evidence based guidelines for pancreatic metastectomy. However, reports in the literature suggest a considered approach to resecting patients with limited disease, favourable tumour type and a significant disease free interval. The aim of this study was to examine the indications and outcomes of pancreatic resection for metastatic disease and non-pancreatic, non-neuroendocrine malignancy at a high-volume pancreatic surgery centre.

Methods

This is a retrospective analysis of a prospectively managed database of pancreatic resections for metastatic disease or primary non-pancreatic, non-neuroendocrine tumours at a single institution. Data collected and analysed included patient demographics, operative details and peri-operative outcomes, subsequent survival and mode of recurrence.

Results

Records of 711 patients who underwent pancreatic resection were examined. 21 consecutive patients met the inclusion criteria, representing 3% of the unit’s throughput. The perioperative morbidity and mortality were 33% and 0% respectively. Overall survival was 86months (95%CI 63-107) for renal cell carcinoma and 64months for other tumours.

Conclusions

When coupled with the low morbidity and mortality rates of a high-volume pancreatic surgery centre using careful patient selection, pancreatic metastectomy has the potential to result in good long-term survival. Recent improvement in the efficacy of systemic therapies, particularly for renal cell carcinoma and melanoma contribute to the utility of resection and to the improved survival of patients.

Postfilament supercontinuum on 100 m path in air

Pulses at 744 nm with 90 fs duration, 6 mJ energy, and a weakly divergent wavefront propagate for more than 100 m and generate a filament followed by an unprecedently long high intensity (≥1TW/cm²) light channel. Over a 20 m long sub-section of this channel, the pulse energy is transferred continuously to the infrared wing, forming spectral humps that extend up to 850 nm. From 3D+time carrier-resolved simulations of 100 m pulse propagation, we show that spectral humps indicate the formation of a train of femtosecond pulses appearing at a predictable position in the propagation path.

Fifteen meter long uninterrupted filaments from sub-terawatt ultraviolet pulse in air

A technique is presented to create uninterrupted long ultraviolet filaments in air using appropriately structured transmission mesh. The mesh with different cell sizes was inserted into 10-cm parallel beam of 0.2-J, 248-nm, and 870-fs pulse propagating along ~100-m corridor. Transverse positions of multiple filaments formed by the optimum size cells were reproducible within at least 15 m along the propagation path. 3D+time simulations confirmed uninterrupted plasma channels with fixed positions in the transverse space similar to the experiment. Unoptimized cell size resulted in filaments shifting towards the cell center and destruction of uninterrupted filaments.

Corona discharge induced snow formation in a cloud chamber

Artificial rainmaking is in strong demand especially in arid regions. Traditional methods of seeding various Cloud Condensation Nuclei (CCN) into the clouds are costly and not environment friendly. Possible solutions based on ionization were proposed more than 100 years ago but there is still a lack of convincing verification or evidence. In this report, we demonstrated for the first time the condensation and precipitation (or snowfall) induced by a corona discharge inside a cloud chamber. Ionic wind was found to have played a more significant role than ions as extra CCN. In comparison with another newly emerging femtosecond laser filamentation ionization method, the snow precipitation induced by the corona discharge has about 4 orders of magnitude higher wall-plug efficiency under similar conditions.

Ultrabroad Terahertz Spectrum Generation from an Air-Based Filament Plasma

We have solved the long-standing problem of the mechanism of terahertz (THz) generation by a two-color filament in air and found that both neutrals and plasma contribute to the radiation. We reveal that the contribution from neutrals by four-wave mixing is much weaker and higher in frequency than the distinctive plasma lower-frequency contribution. The former is in the forward direction while the latter is in a cone and reveals an abrupt down-shift to the plasma frequency. Ring-shaped spatial distributions of the THz radiation are shown to be of universal nature and they occur in both collimated and focusing propagation geometries. Experimental measurements of the frequency-angular spectrum generated by 130-fs laser pulses agree with numerical simulations based on a unidirectional pulse propagation model.

Transformation of terahertz spectra emitted from dual-frequency femtosecond pulse interaction in gases

We demonstrate that the two basic physical mechanisms of terahertz (THz) generation in a femtosecond filament, namely, the free electron photocurrent and the nonlinear polarization of neutrals, can be identified through the spectral analysis of THz radiation. The contribution from the photocurrent peaks at the units of THz, while the neutrals yield the peak at the tens of THz. We suggest the practical implementation of such spectral analysis by varying the initial transform-limited laser pulse duration.

Remote THz generation from two-color filamentation: long distance dependence

Remote terahertz (THz) generation from two-color filamentation is investigated as a function of the onset position of filaments. THz signals emitted by filaments produced at distances up to 55 m from the laser source were measured. However, from 9 m to 55 m, the THz signal decayed monotonically for increasing onset positions. With a simple calculation, the dominant factors associated to this decay were identified as group velocity mismatch of the two-color pulses and linear diffraction induced by focusing and propagating the second harmonic pulse.

Non-radially polarized THz pulse emitted from femtosecond laser filament in air

Femtosecond laser filament could produce THz wave in forward direction. In our experiment, THz pulse emitted from a femtosecond laser filament has been investigated. It was found that the polarization of the studied THz pulse mainly appears as elliptical. This observation supplements the previous conclusion obtained by C. D'Amico et al. that THz wave emitted by a filament is radially polarized. The mechanism of generating elliptically polarized THz wave has been interpreted by either four-wave optical rectification or second order optical rectification inside the filament zone where centro-symmetry of the air is broken by the femtosecond laser pulse.

Experimental and Theoretical Investigation of High-Power Laser Ionization and Dissociation of Methane

The main purpose of this paper is to report the high-power laser ionization-dissociation of CH(4) at various femtosecond (fs) laser intensities (from 1 x 10(14) W/cm(2) to 2 x 10(15) W/cm(2)) with a laser pulse duration of 48 fs. The generalized molecular Keldysh theory has been applied to calculate the ionization yields for CH(4)+ and CH(4)++. Outside the influence of the fs intense laser, we propose to calculate the mass spectra due to the decomposition of CH(4)+ and CH(4)++, using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The agreement between the experimental mass spectra and calculated mass spectra seems to be reasonable.

Bragg gratings photoinduced in ZBLAN fibers by femtosecond pulses at 800 nm

Fiber Bragg gratings were written in thulium-doped and undoped single-mode ZBLAN fibers by focusing femtosecond laser pulses on the fiber core through a phase mask. Maximum index modulation of the order of 1 x 10(-3) was induced in both types of fibers. Measurements of the transverse refractive index changes across the core and cladding regions indicate that the grating formation originates from a negative index change.

Simple 3-D characterization of ultrashort laser pulses

The space and time distribution of electromagnetic energy is essential information for any laser pulse applications that require precision. Although many instruments quantify the temporal profile of ultrashort laser pulses, they are generally limited to space-averaged measurement. In this work, we present an extremely simple technique to characterize the spatial distribution of fluence, pulse duration and chirp of ultrashort light pulses. This technique is based upon imaging the two-photon fluorescence distribution generated by the laser pulse as it propagates through a dispersive medium. It is expected that this technique will provide to less specialized users a precise in-situ analysis of their ultrashort laser beam.

Remote time-resolved filament-induced breakdown spectroscopy of biological materials

We report, for what we believe to be the first time, on the feasibility of remote time-resolved filament-induced breakdown spectroscopy (FIBS) of biological materials. The fluorescence from egg white and yeast powder, induced by femtosecond laser pulse filamentation in air, was detected in the backward direction with targets located 3.5 m away from the detection system. The remarkably distinct spectra of egg white and yeast allow us to propose that this technique, time-resolved FIBS, could be potentially useful for remote detection and identification of harmful biological agents.

Transverse evolution of a plasma channel in air induced by a femtosecond laser

We investigate the evolution of filamentation in air by using a longitudinal diffraction method and a plasma fluorescence imaging technique. The diameter of a single filament in which the intensity is clamped increases as the energy of the pump light pulse increases, until multiple filaments appear.

Nonlinear propagation of fs laser pulses in liquids and evolution of supercontinuum generation

Nonlinear propagation of fs laser pulses in liquids and the dynamic processes of filamentation such as self-focusing, intensity clamping, and evolution of white light production have been analyzed by using one- and two-photon fluorescence. The energy losses of laser pulses caused by multiphoton absorption and conical emission have been measured respectively by z-scan technique. Numerical simulations of fs laser propagation in water have been made to explain the evolution of white light production as well as the small-scale filaments in liquids we have observed by a nonlinear fluorescence technique.

Destruction of polymer growth substrates for cell cultures in two-photon microscopy

The choice of the growth substrate for cell cultures used in fluorescence microscopy is guided by several factors including the type of cells studied and the type of microscopy used. Usually, cells can be cultured on either polymer or glass substrates. One type of polymer, termed Aclar, presents several attractive features: the adhesive properties are better than those of glass, the optical properties are comparable to those of glass, it is biochemically inert, unbreakable, flexible and has a high surface tension, convenient for seeding cells on the cover slip. However, here we show that when imaging with two-photon microscopy, which is based on a femtosecond pulsed laser source, local damage of the Aclar substrate occurs, starting at an average intensity of 10(5) W cm(-2) at the focal point and for exposure times insufficient to cause cell damage. This leads to the appearance of gas bubbles on cultures plated on Aclar cover slips, which perturb the imaging. By contrast, this phenomenon does not occur on borosilicate cover slips, probably because of their different physical (thermal conductivity, absorbance, melting point) and material homogeneity properties. Thus, for cell culture applications using pulsed lasers with high intensities, the use of glass is preferable to Aclar. The results also reveal that substrates can be more susceptible to thermal damage than the cells themselves.

Experiment and simulations on the energy reservoir effect in femtosecond light filaments

We report the results of an experiment and numerical simulations that demonstrate the large spatial extent and the effect of the so-called energy reservoir during the filamentation of femtosecond laser pulses in air. By inserting pinholes of different sizes in the filament path we observe different stages of development ranging from the termination of the filament, through its partial survival, to undisturbed propagation. A background containing up to 50% of the pulse energy is found to be necessary to maintain the filament formation, including a first refocusing.

Ultra-broad and coherent white light generation in silica glass by focused femtosecond pulses at 1.5 um

We report on the observation of efficient and ultra-broadband white light supercontinuum generated by focusing femtosecond pulses from an optical parametric amplifier at 1.5 microm in silica glass. The characteristic white light spectrum is extending from 400 nm up to at least 1750 nm. At sufficiently high input powers stable white light patterns associated with the interference of spatially coherent filamentary sources were observed and analyzed. Unlike focusing with 800 nm pulses from a Ti-sapphire laser, the stable fringes formed for each spectral component were pronounced owing to significantly reduced destructive impact of optical breakdown on filamentation of femtosecond pulses at 1.5 microm. By taking advantage of this property, the formation of optical waveguides in silica glass with considerably broader range of writing parameters as compared to those fabricated with 800 nm pulses, was demonstrated.

Sensing of Halocarbons Using Femtosecond Laser-Induced Fluorescence

A femtosecond laser-induced clean fluorescence technique was explored as a means to monitor halogenated alkanes in the atmosphere. Characteristic difluorocarbene radical (CF2) fluorescence in the UV-vis can be generated inside a femtosecond laser-induced filament for different halocarbons. We show that, due to different dissociation and excitation kinetics leading to fluorescence emission, it is possible to temporally resolve the characteristic fluorescence of CF2-containing halocarbons from that of background species, therefore enhancing the signal-to-noise ratio. Laboratory-scale experiments demonstrate the potential use of femtosecond laser-induced clean fluorescence for the remote sensing of halocarbons in the atmosphere. The combination of this detection strategy with LIDAR could allow the long-range monitoring of several atmospheric species with a single laser source, eventually leading to a better understanding of chemical and dynamic processes affecting global warming, ozone loss, tropospheric pollution, and weather prediction.

Optical breakdown versus filamentation in fused silica by use of femtosecond infrared laser pulses

The competition between optical breakdown (OB) and laser-pulse filamentation (FL) in bulk fused silica is investigated by using a 1-kHz femtosecond infrared laser. We measure input powers corresponding to the threshold of OB and FL in terms of external focusing conditions. The results demonstrate that OB precedes FL for tight focusing, whereas for sufficiently long focal lengths FL takes places at a lower power than OB does.

Third-harmonic generation and self-channeling in air using high-power femtosecond laser pulses

It is shown, both theoretically and experimentally, that during laser pulse filamentation in air an intense ultrashort third-harmonic pulse is generated forming a two-colored filament. The third-harmonic pulse maintains both its peak intensity and energy over distances much longer than the characteristic coherence length. We argue that this is due to a nonlinear phase-locking mechanism between the two pulses in the filament and is independent of the initial material wave-vector mismatch. A rich spatiotemporal propagation dynamics of the third-harmonic pulse is predicted. Potential applications of this phenomenon to other parametric processes are discussed.

Femtosecond pulse propagation in air: variational analysis

We use a variational method to study the phenomenon of intense femtosecond pulse propagation in air. This method allows us to obtain a semianalytical solution to the problem in which a wide range of initial conditions can be studied. In addition, it provides a simple physical interpertation, where the problem is reduced to an analogous problem of a particle moving in a potential well. Different types of possible solutions are considered, with focus upon the main physical interpretations. The results recapture at least qualitatively some of the major experimental observations, and previous numerical simulations.

Conical emission from laser plasma interactions in the filamentation of powerful ultrashort laser pulses in air

We performed detailed experimental and numerical investigations of the conical emission (CE) accompanying the filamentation of powerful ultrashort laser pulses in air. It was found that the CE originates from self-phase modulation in the plasma produced by the pulse during propagation. The experiment and the simulation agree on the essential features of the CE: The CE angle decreases with increasing wavelength and is independent of the position along the filament, and there is no CE at Stokes-shifted wavelengths.

Moving focus in the propagation of ultrashort laser pulses in air

The long light filaments generated in air by powerful ultrashort laser pulses, previously attributed to self-channeling, were investigated by use of gigawatt pulses from a Ti:sapphire chirped-pulse-amplification laser system. A filament contained only a small fraction of the pulse energy and always ended at the diffraction length of the beam (~100 m), independently of the pulse energy. These features are explained by the moving-focus model, which is presented as an alternative to the self-channeling model. Computer simulations involving ionization of the air also support the moving-focus model.

Generation of H(2), O(2), and H(2)O(2) from water by the use of intense femtosecond laser pulses and the possibility of laser sterilization

An intense femtosecond Ti-sapphire laser pulse was focused into water, leading to self-focusing. Apart from generating a white light (supercontinuum), the intense laser field in the self-focusing regions of the laser pulse dissociated the water molecules, giving rise to hydrogen and oxygen gas as well as hydrogen peroxide. Our analysis shows that the formation of free radicals O, H, and OH preceded the formation of the stable products of H(2), O(2), and H(2)O(2). Because O radicals and H(2)O(2) are strong oxydizing agents, one can take advantage of this phenomenon to design a laser scheme for sterilization in medical and biological applications.

Operational stabilization of a high-power ultrashort dye oscillator-amplifiers laser chain

Stable operation of a high-power ultrashort dye laser chain is achieved with an inexpensive heating technique. The femtosecond oscillator and its pumping laser are separately covered with boxes to isolate them from external temperature fluctuations. Both laser-isolating boxes are lined with a heating pellicle that permanently and uniformly warms the lasers to preset operating temperatures. The power, spectrum, and duration of the laser-chain output pulse remain constant from day to day. This technique could be applied to other ultrafast laser devices that require long-term performance stability.

Supercontinuum generation versus optical breakdown in CO(2) gas

Threshold powers for optical breakdown (OB) and supercontinuum (SC) generation in high-pressure CO(2) gas have been measured at different focusing conditions. It has been found that by varying the focal length of the focusing lens, it is possible to pass from the case of OB without SC generation, through OB with SC generation, and into SC without OB. The experimental results demonstrate that plasma formation is not an essential mechanism for SC generation, whereas self-focusing causes SC generation characteristics to be dependent on conditions of external focusing.

Spectral modulation of two coherently separated femtosecond laser pulses

A train of 150-fs 76-MHz pulses is directed into a Michelson interferometer with a path difference larger than the pulse spatial length. A modulated spectrum with a modulation frequency that increases with the path difference is observed. The consequence is discussed.

Spot-size measurement of an intense CO(2) laser beam

The determination of a high-power CO(2) laser beam spot size is described. The method consists of measuring burn pattern radii in holographic emulsion as a function of laser pulse energy.

Stable operation of a powerful 3-Hz line tunable TEA CO(2) oscillator-amplifiers system

We communicate results of the stable operation of a TEA CO(2) oscillator-amplifiers system, producing pulses of 10(14) W/cm(2) at best focus, furnished with a simple provision for retropulse isolation.

Nonlinear refraction in CS(2) at 10.6 microm

The nonlinear refractive index n(2) of CS(2) at 10.6 microm, the value of which is a subject of a recent controversy, is measured by an external self-focusing method. We found that n(2) = (2.1 +/- 0.7) x 10(-11) esu, similar to the accepted value of n(2) in the visible. Self-bending of spatially asymmetric CO(2) laser beam in CS(2) due to an ultrafast Kerr effect is observed, and the deduced value of n(2) is in agreement with our results.

Simultaneous nonlinear absorption and index effects in the propagation of intense TEA CO2 laser pulses through CDF3

Changes in the beam profile of the CO2 laser 10R(26) line, caused by transmission through, and absorption by, CDF3 were studied using an array of pyroelectric detectors. During the propagation of the laser beam through CDF3, nonlinear absorption and self-defocusing of the beam have both been determined from measurements of the effect on the exit beam of fluence, radiant energy, CDF3 pressure, transmission cell length, and distance from the exit of the cell to the detector array.

Single-pulse photoacoustic technique for measuring IR multiphoton absorption by polyatomic molecules

The single-pulse photoacoustic technique was used to measure cross sections for IR multiphoton absorption. A discussion of this technique and the applicable pressure range is given. The source of the signals from the microphone was identified. The first peak is proportional to the energy absorbed by the gas in the focal region, while the subsequently arriving signals correspond to a mixture of the signal from the entrance and exit volumes and the ringings of the microphone and the gas cell.

Self-focusing of CO(2) laser pulses in low-pressure SF(6)

We point out the importance of intensity-dependent refractive-index effects when measuring transmission or absorption characteristics of gases with high-power TEA CO(2) laser pulses. An example is given showing how self-focusing in low-pressure SF(6) gas severely affected the transmission of a Gaussian beam. This effect increased rapidly with pressure but remained unchanged when the TEA CO(2) fluence varied from 0.3 to 1.0 J/cm(2).