Second harmonic generation imaging of collagen scaffolds within the alveolar ducts of healthy and emphysematous mouse lungs.

The alveolar ducts are connected to peripheral septal fibers which extend from the visceral pleura into interlobular septa, and are anchored to axial fibers in the small airways. Together these axial and septal fibers constitute a fiber continuum that provides tension and integrity throughout the lung. Building on the observations that alveolar ducts associated with sub-pleural alveoli are orientated perpendicular to the visceral pleura, and in parallel to each other, the goal of the present study was to investigate the nature of the collagen fiber organization within sub-pleural alveolar ducts in healthy control and elastase-induced emphysema murine lungs. Employing three-dimensional second harmonic generation imaging, the structural arrangement of fibrilar collagen fibers could be visualized in cleared murine lungs. In healthy control lungs, fibrilar collagen fibers within alveolar mouths formed the coiled collagen structure within the alveolar duct. In the elastase-treated emphysema lungs, there was loss of fibrilar collagen fibers (p < 0.01) and disruption of collagens structural organization as measured by the fibrillar collagen length (p < 0.01) and entropy (p < 0.01). Compared to the alveolar ducts from healthy controls, there was a significant increase in the area of cells (nm2, p < 0.001), and area of cells with cytoplasmic granules (nm2, p < 0.001) compared to emphysematous lungs. These results are consistent with the idea that one of the major contributors to the progressive loss of alveolar surfaces and elastic recoil in the emphysematous lung is loss of the structural integrity of the collagen scaffold that maintains the spatial relationships important for cell survival and lung function.

Performance of the TRUE dilatation balloon valvuloplasty catheter beyond rated burst pressure: A bench study.

OBJECTIVES: We undertook an independent bench test assessing the performance of the TRUE dilatation (TD) balloon valvuloplasty catheter (Bard Vascular Inc., Tempe, AZ) beyond its rated burst pressure (RBP). BACKGROUND: The TD balloon has a RBP of six atmospheres (atm), and its performance beyond this RBP is poorly understood. Techniques such as bioprosthetic valve fracture require inflation pressures beyond manufacturer recommendations. METHODS: A 20, 22, 24, 26, and 28 mm TD balloon were inflated to increasing pressures in increments of 3 atm until balloon failure. Measurements were performed at the proximal, middle, and distal balloon segments with scientific digital calipers. Z-MED balloons (Braun Interventional Systems Inc., Bethlehem, PA) were used as a comparator. RESULTS: The mean diameter at the middle of the 20, 22, 24, 26, and 28 mm TD balloon at nominal pressure (3 atm) was 20.02 ± 0.09, 21.77 ± 0.07, 23.9 ± 0.06, 25.82 ± 0.08, and 27.62 ± 0.08 mm, respectively. The maximal mean diameter at the middle of the 20, 22, 24, 26, and 28 mm TD balloon was 20.39 ± 0.03 mm (15 atm), 22.35 ± 0.03 mm (15 atm), 24.55 ± 0.02 mm (15 atm), 26.48 ± 0.02 mm (12 atm), and 28.39 ± 0.03 mm (12 atm), respectively. The 20/22/24 and 26/28 mm balloon failed when inflated beyond 15 atm and 12 atm, respectively. Failure was due to either leakage or longitudinal balloon rupture. TD balloons were more likely to maintain dimensions similar to their labeled size and less likely to fail at higher pressures as compared to Z-MED balloons. CONCLUSION: The TD balloon catheter maintains a similar diameter to its labeled size, when inflated beyond its RBP. When inflated beyond 12 atm, the TD balloon can fail due to either leakage or rupture. This has implications for percutaneous structural heart interventions.

Overexpansion of older generation balloon expandable transcatheter heart valves: An ex-vivo bench study.

BACKGROUND: The SAPIEN 3 (S3) transcatheter heart valve (THV) can be over-expanded beyond its labeled diameter. Overexpansion can be achieved with use of either a compliant or non-compliant balloon. Objective data regarding the ability to over-expand older generation balloon expandable valves are limited. We sought to assess the effects of over-expanding the SAPIEN and SAPIEN XT (Edwards Lifesciences, Irvine, CA) valve beyond labeled size (diameter) through an ex-vivo bench study. METHODS AND RESULTS: We assessed SAPIEN and SAPIEN XT THVs, sized 23/26 mm and 23/26/29 mm, respectively. The SAPIEN THVs were explanted samples. Valves were expanded to nominal dimensions, and then incrementally overexpanded with balloons sized 1-, 2-, and 3-mm larger than the recommended diameter. When an appropriate sized non-compliant balloon was not available, a compliant balloon was utilized. Valves underwent visual and radiographic assessment of overexpansion. SAPIEN THVs with labeled size of 23 and 26 mm could be incrementally overexpanded to midvalve (MV) diameters of 26.7 and 27.4 mm, respectively. SAPIENT XT THVs with labeled size of 23, 26, and 29 mm could be incrementally overexpanded to MV diameters of 26.8, 28.3, and 28.8 mm, respectively. The desired degree of overexpansion was only achieved with use of non-compliant balloons and not with compliant balloons. The outflow of the SAPIEN and SAPIEN XT had larger diameters than the MV and inflow of the THV. CONCLUSION: Overexpansion of older generation SAPIEN and SAPIEN XT THVs is possible. Achieving the desired degree of overexpansion was only achieved with use of non-compliant balloons. This has potential implications for the treatment of failed THVs.

Spatial-spectral coupling in coherent anti-Stokes Raman scattering microscopy.

Coherent anti-Stokes Raman scattering (CARS) microscopy is a third-order nonlinear optical technique which permits label-free, molecule-specific hyperspectral imaging. The interference between coherent resonant and non-resonant terms leads to well known distortions in the vibrational spectrum, requiring the use of retrieval algorithms. It also leads to spatial imaging distortions, largely due to the Gouy phase, when objects are smaller than the Rayleigh range. Here we consider that the focal position and spectral contributions to the nonlinear image formation are intrinsically coupled and cannot be corrected by conventional retrieval methods.

Coronary Access Following Redo TAVR: Impact of THV Design, Implant Technique, and Cell Misalignment.

BACKGROUND: The implications and potential challenges of coronary access after redo transcatheter aortic valve replacement (TAVR) are unknown. OBJECTIVES: The authors sought to evaluate the impact of different transcatheter heart valve (THV) designs, neoskirt height, implant technique, and cell misalignment on coronary access after redo TAVR. METHODS: Different THV designs (Sapien 3 [Edwards Lifesciences LLC], Evolut Pro [Medtronic], ACURATE neo [Boston Scientific Corporation], and Portico [Abbott Structural Heart]) and sizes were implanted inside Sapien XT (Edwards Lifesciences LLC) and Evolut R (Medtronic) THVs, which were modeled as the "failed" THVs, at different implant depths. Valve combinations underwent micro-computed tomography to determine the neoskirt height and dimensions of the lowest accessible cell for potential coronary access. This was compared with dimensions of 6-F/7-F/8-F coronary guiding catheters. RESULTS: Redo TAVR combinations resulted in a wide range of neoskirt heights (15.4-31.6 mm) and a variable diameter of the lowest accessible cell (1.9-21.8 mm). An ACURATE neo implanted in a Sapien XT resulted in the largest accessible cells, whereas a Portico implanted in a Sapien XT resulted in the lowest neoskirt heights. The smallest accessible cell was observed in the Evolut Pro-in-Evolut R configuration with higher neoskirt heights. Redo TAVR in a tall frame valve with supra-annular leaflets caused a taller neoskirt height. In Evolut-in-Evolut combinations, misalignment of the cells of the 2 THVs reduced the cell area by 30% to 50% compared with an aligned configuration. CONCLUSIONS: This study demonstrates that different redo TAVR combinations are not equivalent in terms of future coronary access. Redo TAVR using a tall frame valve in a failed tall frame valve and misaligned cells may lead to potentially challenging coronary access.

Super resolution measurement of collagen fibers in biological samples: Validation of a commercial solution for multiphoton microscopy.

Multiphoton microscopy is a powerful, non-invasive technique to image biological specimens. One current limitation of multiphoton microscopy is resolution as many of the biological molecules and structures investigated by research groups are similar in size or smaller than the diffraction limit. To date, the combination of multiphoton and super-resolution imaging has proved technically challenging for biology focused laboratories to implement. Here we validate that the commercial super-resolution Airyscan detector from ZEISS, which is based on image scanning microscopy, can be integrated under warranty with a pulsed multi-photon laser to enable multiphoton microscopy with super-resolution. We demonstrate its biological application in two different imaging modalities, second harmonic generation (SHG) and two-photon excited fluorescence (TPEF), to measure the fibre thicknesses of collagen and elastin molecules surpassing the diffraction limit by a factor of 1.7±0.3x and 1.4±0.3x respectively, in human heart and lung tissues, and 3-dimensional in vitro models. We show that enhanced resolution and signal-to-noise of SHG using the Airyscan compared to traditional GaAs detectors allows for automated and precise measurement of collagen fibres using texture analysis in biological tissues.

A bench test study of bioprosthetic valve fracture performed before versus after transcatheter valve-in-valve intervention.

AIMS: Bioprosthetic valve fracture (BVF) may improve transvalvular gradients and transcatheter heart valve (THV) expansion during VIV interventions. However, the optimal timing of BVF is unknown. We assessed the impact of timing of BVF (before versus after) for valve-in-valve (VIV) intervention, on hydrodynamic function and THV expansion. METHODS AND RESULTS: Three THV designs were assessed, a 23 mm SAPIEN 3 (S3), small ACURATE neo (ACn) and 23 mm Evolut R, deployed into 21 mm Mitroflow bioprosthetic surgical valves. We evaluated each THV in three groups: 1) no BVF, 2) BVF before VIV, and 3) BVF after VIV. Hydrodynamic testing was performed using a pulse duplicator to ISO 5840:2013 standard. Transvalvular gradients were lower when BVF was performed after VIV for the S3 (no BVF 15.5 mmHg, BVF before VIV 8.0 mmHg, BVF after VIV 5.6 mmHg), and the ACn (no BVF 9.8 mmHg, BVF before VIV 8.4 mmHg, BVF after VIV 5.1 mmHg). Transvalvular gradients were similar for the Evolut R, irrespective of performance of BVF or timing of BVF. BVF performed after VIV resulted in better expansion in all three THV designs. The ACn and Evolut R samples all had a mild degree of pinwheeling, and BVF timing did not impact on pinwheeling severity. The S3 samples had severe pinwheeling with no BVF, and significant improvement in pinwheeling when BVF was performed after VIV. CONCLUSIONS: BVF performed after VIV was associated with superior THV expansion in all three THV designs tested, with lower residual transvalvular gradients in the S3 and ACn THVs. The Evolut R had similar hydrodynamic performance irrespective of BVF timing. Timing of BVF has potential implications on THV function.

Valve-in-Valve Transcatheter Aortic Valve Replacement and Bioprosthetic Valve Fracture Comparing Different Transcatheter Heart Valve Designs: An Ex Vivo Bench Study.

OBJECTIVES: The authors assessed the effect of valve-in-valve (VIV) transcatheter aortic valve replacement (TAVR) followed by bioprosthetic valve fracture (BVF), testing different transcatheter heart valve (THV) designs in an ex vivo bench study. BACKGROUND: Bioprosthetic valve fracture can be performed to improve residual transvalvular gradients following VIV TAVR. METHODS: The authors evaluated VIV TAVR and BVF with the SAPIEN 3 (S3) (Edwards Lifesciences, Irvine, California) and ACURATE neo (Boston Scientific Corporation, Natick, Massachusetts) THVs. A 20-mm and 23-mm S3 were deployed in a 19-mm and 21-mm Mitroflow (Sorin Group USA, Arvada, Colorado), respectively. A small ACURATE neo was deployed in both sizes of Mitroflow tested. VIV TAVR samples underwent multimodality imaging, and hydrodynamic evaluation before and after BVF. RESULTS: A high implantation was required to enable full expansion of the upper crown of the ACURATE neo and allow optimal leaflet function. Marked underexpansion of the lower crown of the THV within the surgical valve was also observed. Before BVF, VIV TAVR in the 19-mm Mitroflow had high transvalvular gradients using either THV design (22.0 mm Hg S3, and 19.1 mm Hg ACURATE neo). After BVF, gradients improved and were similar for both THVs (14.2 mm Hg S3, and 13.8 mm Hg ACURATE neo). The effective orifice area increased with BVF from 1.2 to 1.6 cm2 with the S3 and from 1.4 to 1.6 cm2 with the ACURATE neo. Before BVF, VIV TAVR with the ACURATE neo in the 21-mm Mitroflow had lower gradients compared with S3 (11.3 mm Hg vs. 16 mm Hg). However, after BVF valve gradients were similar for both THVs (8.4 mm Hg ACURATE neo vs. 7.8 mm Hg S3). The effective orifice area increased from 1.5 to 2.1 cm2 with the S3 and from 1.8 to 2.2 cm2 with the ACURATE neo. CONCLUSIONS: BVF performed after VIV TAVR results in improved residual gradients. Following BVF, residual gradients were similar irrespective of THV design. Use of a small ACURATE neo for VIV TAVR in small (≤21 mm) surgical valves may be associated with challenges in achieving optimum THV position and expansion. BVF could be considered in selected clinical cases.

Overexpansion of the SAPIEN 3 Transcatheter Heart Valve: An Ex Vivo Bench Study.

OBJECTIVES: This study assessed the effect of overexpansion beyond labeled size (diameter) of transcatheter heart valves through an ex vivo bench study. BACKGROUND: Transcatheter heart valves function optimally when expanded to specific dimensions. However, clinicians may sometimes wish to overexpand balloon-expandable valves to address specific clinical challenges. The implications of overexpansion have assumed considerable importance, and objective information to guide practice is limited. METHODS: We evaluated SAPIEN 3 transcatheter heart valves (Edwards Lifesciences, Irvine, California). Valves (diameters of 23, 26, and 29 mm) were expanded to nominal dimensions, and then incrementally overexpanded with balloons sized 1-, 2-, and 3-mm larger than the recommended diameter. Valves underwent visual, microcomputed tomography, and hydrodynamic evaluation at various degrees of overexpansion. RESULTS: SAPIEN 3 valves with labeled diameters of 23, 26, and 29 mm could be incrementally overexpanded to midvalve diameters of 26.4, 28.4, and 31.2 mm, respectively. With overexpansion, there was visible restriction of the valve leaflets, which was particularly evident with the smaller valves. After maximal overexpansion of a 26-mm valve a leaflet tear was observed. High-speed video demonstrated impaired leaflet motion of both the 23- and 26-mm valves and hydrodynamic testing documented a regurgitant fraction for the 23- and 26-mm valves above accepted international standards. The maximally overexpanded 29-mm SAPIEN 3 still had relatively normal leaflet motion and excellent hydrodynamic function. Durability was not specifically evaluated. CONCLUSIONS: Overexpansion of balloon-expandable valves is possible. However, excessive overexpansion may be associated with impaired hydrodynamic function, acute leaflet failure, and reduced durability. Smaller valves may be at greater risk with overexpansion than larger valves. Overexpansion is best avoided unless clinical circumstances are compelling.

Label-free hyperspectral nonlinear optical microscopy of the biofuel micro-algae Haematococcus Pluvialis.

We consider multi-modal four-wave mixing microscopies to be ideal tools for the in vivo study of carotenoid distributions within the important biofuel microalgae Haematococcus pluvialis. We show that hyperspectral coherent anti-Stokes Raman scattering (CARS) microscopy generates non-invasive, quantitative real-time concentrations maps of intracellular carotenoid distributions in live algae.