Feasibility of multiplane microtransoesophageal echocardiographic guidance in structural heart disease transcatheter interventions in adults.

INTRODUCTION: Structural heart interventions are guided by transoesophageal or intracardiac echocardiography (TEE/ICE). MicroTEE, developed for paediatric purposes, is smaller and therefore less invasive and traumatic, avoiding the need for general anaesthesia. We aimed to show feasibility of procedural guidance by comparing image quality of microTEE with standard TEE and ICE during adult transcatheter interventions, and assess the accuracy in obtaining left atrial appendage (LAA) measurements between the microTEE probe and standard TEE. METHODS AND RESULTS: We prospectively included 49 patients (20 women, 64 ± 18 years). Intraprocedural images were obtained by using the microTEE probe and standard (2D and 3D) TEE (LAA closure, MitraClip implantation) or ICE (interatrial communication closure, transseptal puncture for left atrial ablation). Two echocardiographers independently assessed image quality from 1 (excellent) to 4 (poor) and performed LAA measurements. Use of microTEE was not related to significant discomfort. Image quality obtained with the microTEE probe was lower than with standard TEE (2 [1-2] vs. 1 [1-2]; p = 0.04) and comparable with ICE images (2 [1-2] vs. 2 [1-2], p = 0.13). MicroTEE showed a wider field of view than ICE. LAA measurements on images obtained by microTEE were strongly associated with standard TEE. CONCLUSIONS: MicroTEE seems feasible for guidance during transcatheter heart interventions in adults. MicroTEE imaging offers a wider field of view than ICE, and its accuracy is comparable with TEE. In transcatheter interventions performed under conscious sedation, microTEE might be a viable and advantageous alternative to standard TEE or ICE.

Evaluation of a real-time hybrid three-dimensional echo and X-ray imaging system for guidance of cardiac catheterisation procedures.

Minimally invasive cardiac surgery is made possible by image guidance technology. X-ray fluoroscopy provides high contrast images of catheters and devices, whereas 3D ultrasound is better for visualising cardiac anatomy. We present a system in which the two modalities are combined, with a trans-esophageal echo volume registered to and overlaid on an X-ray projection image in real-time. We evaluate the accuracy of the system in terms of both temporal synchronisation errors and overlay registration errors. The temporal synchronisation error was found to be 10% of the typical cardiac cycle length. In 11 clinical data sets, we found an average alignment error of 2.9 mm. We conclude that the accuracy result is very encouraging and sufficient for guiding many types of cardiac interventions. The combined information is clinically useful for placing the echo image in a familiar coordinate system and for more easily identifying catheters in the echo volume.

Characterization of portwine stain disfigurement.

Portwine stain disfigurement is caused by several factors. To what extent and in which proportion these factors influence the overall perceived disfigurement is incompletely understood. In this study, the contribution of seven portwine stain characteristics to overall portwine stain disfigurement was assessed. Color slides were taken from 90 patients with untreated portwine stains in the head/neck area. From these slides, overall portwine stain disfigurement was judged by a panel of 16 lay persons. The reliability of the average ratings of this panel was established with weighted kappa analysis (kappa = 0.51) and by calculating the Cronbach alpha coefficient (0.99). Using a previously tested multi-item questionnaire, the following portwine stain characteristics were rated quantitatively by a panel of five professionals: color, patchiness, boundary, size, shape, surface structure, and hypertrophy of the underlying tissue. By means of multiple linear regression analysis, the ratings for overall portwine stain disfigurement (panel of lay persons) were compared with the ratings for the individual portwine stain characteristics (panel of professionals). From the results of this analysis, the percentual contribution of each of the characteristics to overall portwine stain disfigurement was calculated. Size turned out to be the most important portwine stain characteristic, being responsible for almost half of the overall disfigurement. Color and boundary are the next two most important characteristics, contributing 18.7 and 12.4 percent, respectively. The other four characteristics together account for 10 percent. In our model, 13 percent of overall portwine stain disfigurement remains unexplained. We expect patient features to account for this. We feel that these results may have consequences for laser treatment of portwine stains. Reducing the size and fading out the boundary of the stain probably reduce overall portwine stain disfigurement more effectively than primarily trying to lighten the often persistent center of the stain.

Assessment of clinical outcome after flashlamp pumped pulsed dye laser treatment of portwine stains: a comprehensive questionnaire.

A generally accepted method to assess the clinical outcome of laser treatment of portwine stains is not available. This paper describes the development and evaluation of a comprehensive questionnaire for the assessment of the following portwine stain characteristics: color (hue and lightness), sharpness of boundary, pigmentation, size, shape, skin surface-structure, and hypertrophy of underlying tissue. The questionnaire was applied to photographs of 70 patients with previously untreated portwine stains in the head/neck area. Photographs were taken before treatment and after five treatments of the entire portwine stain with a flashlamp pumped pulsed dye laser. Each photograph was evaluated separately by a panel of five professionals: the treating physician, two plastic surgeons, a dermatologist, and a clinical photographer. Treatment results were assessed by comparing ratings before and after treatment. Agreement among raters was acceptable for all portwine stain characteristics, as was shown by weighted kappa analysis. The reliability of the answers was further improved by taking the average rating of the five panel members. The scores thus obtained were very reliable, with Cronbach alpha coefficients of 0.8 on average. After five treatments of the entire portwine stain, the most considerable changes were measured in the ratings for color (lightening of the stain by 33 percent), boundary (sharpness reduced by 38 percent), and size (13-percent decrease). Using the questionnaire can be helpful in the design of comparative clinical trials on portwine stain treatment and may facilitate comparison of treatment results between different treatment centers and/or different lasers.

Recanalization of chronic total coronary occlusions using a laser guide wire: a pilot study.

OBJECTIVES: This study sought to prospectively evaluate the performance of a laser guide wire in crossing chronic total coronary occlusions in patients with a failed previous mechanical guide wire attempt. BACKGROUND: Despite continued refinement of mechanical hardware available for coronary angioplasty, restoration and maintenance of blood flow through a chronically occluded coronary artery remains a true challenge. METHODS: Fifty patients with a chronic total coronary occlusion and a previous failed attempt at recanalization using mechanical guide wires were included. A mechanical attempt to cross the occlusion was repeated. In case of failure, an additional attempt was made with the laser guide wire. RESULTS: The median age of occlusion was 22 weeks (range 5 to 200), and the occlusion length was 23 +/- 11 mm (mean +/- SD). A repeat mechanical attempt was successful in six cases (12%). Dissection occurred in five other cases, and device crossover was not attempted. Thus, in 39 patients an attempt was made with the laser guide wire, with successful recanalization in 23 (59%). Thereby the overall success rate increased from 12% to 58% (29 of 50 patients). The amount of contrast medium used was 515 +/- 154 ml, fluoroscopy time was 99 +/- 43 min, and total procedure time was 2 h 48 min (+/- 55 min). Procedural success was achieved in 26 cases and clinical success (procedural success without in hospital events) in 24. In-hospital events were two non-Q wave myocardial infarctions related to subacute reocclusion. In one patient, a balloon dilation after laser guide wire perforation resulted in tamponade requiring pericardiocentesis. After a successful procedure, the angina class decreased from 2.9 +/- 0.2 to 1.4 +/- 0.7 at 3 months of clinical follow-up. Six month angiographic follow-up was completed in all 24 eligible patients and showed vessel patency in 20 (80%). CONCLUSIONS: The use of the laser guide wire for recanalization of chronic total coronary occlusions refractory to treatment with mechanical guide wires is feasible and relatively safe and was successful in 59% of cases. This device must thus be considered a valuable addition to the interventional armamentarium and accordingly will be evaluated in a randomized clinical trial.

Uniform irradiation of irregularly shaped cavities for photodynamic therapy.

It is difficult to achieve a uniform light distribution in irregularly shaped cavities. We have conducted a study on the use of hollow 'integrating' moulds for more uniform light delivery of photodynamic therapy in irregularly shaped cavities such as the oral cavity. Simple geometries such as a cubical box, a sphere, a cylinder and a 'bottle-neck' geometry have been investigated experimentally and the results have been compared with computed light distributions obtained using the 'radiosity method'. A high reflection coefficient of the mould and the best uniform direct irradiance possible on the inside of the mould were found to be important determinants for achieving a uniform light distribution.

Homogeneous light distribution to reduce vessel trauma during excimer laser angioplasty.

Excimer laser coronary angioplasty (ELCA) is associated with vascular damage, caused by rapidly expanding water vapour bubbles and accumulation of insoluble gas. The size of the rapidly expanding bubbles and the volume of gas can be reduced by decreasing the laser pulse energy density. However, using current multifibre catheters, penetration through porcine aortic tissue was found to be impossible at energy densities < or = 45 mJ/mm2. By contrast, by employing a 660 microns bare fibre it was observed that efficient tissue crossing was possible at 12 mJ/mm2, with considerable reduction of the rapidly expanding bubble volume and insoluble gas production. We attribute this efficient tissue penetration at low energy densities to the absence of 'dead space' in the homogeneous light distribution (HLD) at the fibre tip. Accordingly we hypothesize the ELCA performed at lower energy densities may result in less mechanical trauma to the vessel wall when compared with ELCA using current multifibre catheters.

Tissue ablation and gas formation of two excimer laser systems: an in vitro evaluation on porcine aorta.

BACKGROUND AND OBJECTIVE: The relationship between tissue ablation volume and the formation of insoluble gas of the currently available excimer laser systems is unknown. This aspect was evaluated in two excimer laser systems. STUDY DESIGN/MATERIALS AND METHODS: We measured tissue ablation volume and gas production of two excimer laser systems (308 nm) on porcine aortic tissue immersed in saline (the CVX-300 using 1.4 and 1.7 mm laser catheters and the Dymer 200 + using 1.3, 1.3z and 1.6 mm laser catheters). RESULTS: Tissue ablation volume and gas production increased proportionally with the applied energy fluence, ranging from 30-60 mJ/mm2. The gas production per unit of ablated tissue volume of the 1.4 mm laser catheter was significantly higher than the 1.3 mm laser catheter (mean difference +117%, 95% CI from +64% till +188%, P<0.001). The gas production of the 1.7 mm laser catheter was higher than the 1.6 mm laser catheter (mean difference +70%, 95% CI from +28% till +126%, P<0.001). The 1.3z mm laser catheter demonstrated more gas production than the 1.3 mm laser catheter (mean difference +123%, 95% CI from +68% till +196%, P<0.001). CONCLUSION: The results of our study indicate that excimer laser with the use of the CVX-300 laser system results in significantly higher gas production than the Dymer 200+ laser system, which can be markedly reduced by lowering the applied energy fluence. The 1.3z laser catheter constitutes an exception, showing similar characteristics as the CVX-300 laser catheters.

Reduced wound contraction and scar formation in punch biopsy wounds. Native collagen dermal substitutes. A clinical study.

In full-thickness skin wounds dermal regeneration usually fails, resulting in scar formation and wound contraction. We studied dermal regeneration by implantation of collagenous matrices in a human punch biopsy wound model. Matrices were made of native bovine collagen I fibres, and either hyaluronic acid, fibronectin, or elastin was added. Matrices were placed in 6-mm punch biopsy holes in seven patients (biopsies were used for the grafting of leg ulcers), and covered with a protective semi-permeable polyether urethane membrane. Histology, wound contraction and dermal architecture were studied. Dermal architecture was evaluated using a recently developed laser scatter technique. All collagen matrices showed a tendency to reduce wound contraction, compared with control wounds; elastin- and fibronectin-treated matrices showed significantly less contraction than control wounds. Only the addition of elastin had a clear beneficial effect on dermal architecture; collagen bundles were more randomly organized, compared with control wounds, and wounds treated with collagen matrices coated with fibronectin or hyaluronic acid, or without coating. We conclude that the punch biopsy wound model provides important information on dermal regeneration in humans. Native collagen matrices with elastin contributed to dermal regeneration and reduced wound contraction, in contrast with matrices coated with fibronectin or hyaluronic acid, or without coating. Future clinical studies of large-area, full-thickness wounds will be required to establish their clinical relevance for leg ulcer and burn treatment.

Wavelengths for laser treatment of port wine stains and telangiectasia.

BACKGROUND AND OBJECTIVE: This report presents analytical modelling of the influence of wavelength on the amount of volumetric rate of heat produced in dermal blood vessels by millisecond laser radiation. STUDY DESIGN/MATERIALS AND METHODS: A new anatomical model is proposed that represents port wine stains as well as telangiectatic lesions. It consists of a target blood vessel, representing the deepest dermal blood vessel that requires irreversible injury, and a layer of whole blood, representing all other dermal blood vessels above the target vessel. The laser light that interacts with the blood vessels is assumed to be diffuse. Selective photothermolysis is the basis for the analysis. We consider wavelengths between 577 nm and 600 nm, the argon laser wavelengths at 488/515 nm, and the frequency doubled Nd:YAG laser wavelength at 532 nm. RESULTS: The rate of volumetric heat production of absorbed laser light in the target blood vessel is expressed analytically as a function of blood absorption, the concentration of additional dermal blood, and the depth of the target vessel. CONCLUSION: The model explains why 585 nm is a good compromise for treating port wine stains that vary widely in number of dermal blood vessels. It predicts that wavelengths between 577 nm and 582 nm are excellent for the treatment of port wine stains in young children, and it suggests a possible explanation as to why the argon laser is sometimes said to be capable of treating dark mature port wine stains. The copper vapour laser wavelength at 578 nm, and the frequency doubled Nd:YAG laser wavelength at 532 nm, are predicted to be suitable for the treatment of port wine stains that contain, respectively, a small to moderate and a moderate number of dermal blood vessels. When laser beam spotsize becomes smaller, the best wavelength for producing maximal rate of heat in the target vessel is predicted to shift to 577 nm.

Short-term biventricular circulatory support in the regionally stunned pig myocardium.

Mechanical circulatory support is only meaningful when reversible myocardial damage exists. Prompt biventricular assistance during reperfusion for six hours was tried in the regionally sublethally injured pig myocardium which has perspective for recovery. Postmortem tissue was examined with a quickly performed histochemical technique for tissue viability. Animals underwent five coronary occlusions (5 min occlusion/10 min reperfusion). Postischemic systolic wall thickening, observed by direct echocardiography, fell about 50% (p < 0.05 vs base line) before treatment which paralleled cardiac inosine and lactate efflux. Biventricular unloading (n = 5) resulted in contractile recovery to 94 +/- 19% (p < 0.05 vs stunning), untreated pigs remained depressed (33 +/- 12%, n = 5). During circulatory support the arterial lactate levels rose three-fold, concomitant with a drop in pH of 0.2 units (p < 0.05). Post-mortem histochemistry showed scattered areas with decreased activities of cytoplasmic lactate dehydrogenase and mitochondrial beta-hydroxybutyrate dehydrogenase, irrespective of treatment. Transmission electron microscopy revealed irreversible damage to mitochondria in depleted areas in contrast to areas where enzyme activity was present. We conclude that prompt volume unloading during reperfusion accelerated contractile recovery of sublethally postischemic myocardium.

Limits of radial time constants to approximate thermal response of tissue.

The time constant model, as an approximation to the bio-heat equation, was tested for non-ablating, deep penetrating (argon) laser beams in absorbing tissue phantoms (polyacrylamide) in air. Temperature responses were measured with a thermal camera, both during laser irradiation as well as after the laser beam was switched off. The radial time constant model was found to give a reasonable prediction (within 5%) of temperature rise for irradiation times of up to the order of one time constant. The cooling behavior of tissue could not be described by one single time constant. The time constant model was found to fit the early cooling rate (cooling time about equal to irradiation time) for laser pulse durations of up to one time constant. The late cooling rate turned out to be much slower than predicted by the radial time constant model, yet it was faster than the cooling rate predicted by the one-dimensional instantaneous hot cylinder surface model.

Effect of force on ablation depth for a XeCl excimer laser beam delivered by an optical fiber in contact with arterial tissue under saline.

The effect of force applied to a 430 micron single fiber, delivering 60 pulses of 308 nm XeCl laser radiation at 20 Hz, on the ablation depth in porcine aortic tissue under saline has been investigated. Energy densities of 8, 15, 25, 28, 31, 37, and 45 mJ/mm2 were used. Force was applied by adding weights from 0 to 10 grams to the fiber. The fiber penetration was monitored by means of a position transducer. At 0 grams, the ablation depth increased linearly with incident energy density, but the fiber did not penetrate the tissue; with any weight added, the fiber penetrated the tissue at energy densities above 15 mJ/mm2. The fiber did not penetrate during the first several pulses, possibly due to gas trapped under the fiber. After these first pulses, a smooth linear advancement of the fiber began, which lasted until the pulse train stopped. The ablation depth increased with increasing energy densities and weights. This effect was largest above 25 mJ/mm2 where the ablation efficiencies (unit mm3/J), with weights added to the fiber, were substantially larger than values found in 308 nm ablation experiments described in the literature, which were conducted with either a focused laser beam or a fiber without additional force. The results imply that in 308 nm excimer laser angioplasty, force must be applied to the beam delivery catheter for efficient recanalization, and that experiments performed with a focused beam or without actual penetration of the fiber do not represent the situation encountered in excimer laser angioplasty.

CW laser ablation velocities as a function of absorption in an experimental one-dimensional tissue model.

One-dimensional continuous-wave laser tissue ablation models predict that the steady-state ablation velocity is independent of the optical absorption of the tissue and proportional to laser power density. This theoretical result was tested in an experimental model that approximates the one-dimensional situation. The model consists of 3 to 4 mm-diameter polyacrylamide rods irradiated at one end with an argon laser beam with uniform power density. It was found that ablation velocity is indeed independent of the light absorption coefficient in the material and proportional to the incident power density. Analysis of the relation between the experimental velocities and the power density showed that approximately 40% of the incident laser light is reflected or attenuated in the escaping vapors. Furthermore, compared to the actual absorbed laser power, heat loss caused by thermal radiation and convection from the side surface of the rod is considerable during ablation, especially at lower power densities. This heat loss is not present in a true one-dimensional geometry and creates therefore a marked difference between the rod and one-dimensional geometry. Computations show that in the pre-ablation stage the heat losses from the rod can be neglected, compared to the absorbed energy. In this case the rod is a very good approximation of the true one-dimensional situation.

Temperature response of biological materials to pulsed non-ablative CO2 laser irradiation.

This paper presents surface temperature responses of various tissue phantoms and in vitro and in vivo biological materials in air to non-ablative pulsed CO2 laser irradiation, measured with a thermocamera. We studied cooling off behavior of the materials after a laser pulse, to come to an understanding of heat accumulation and related thermal damage during (super) pulsed CO2 laser irradiation. The experiments show a very slow decay of temperatures in the longer time regime. This behavior is well predicted by a simple model for one-dimensional heat flow that considers the CO2 laser radiation as producing a heat flux on the material surface. The critical pulse repetition frequency for which temperature accumulation is sufficiently low is estimated at about 5 Hz. Although we have not investigated the ablative situation, our results suggest that very low pulse frequencies in microsurgical procedures may be recommended.

Wavelength and light-dose dependence in tumour phototherapy with haematoporphyrin derivative.

Red light (c. 630 nm) is almost universally used in tumour phototherapy as it is the most penetrating of the porphyrin excitation wavebands. However, measurements of tumour attenuation of light of different wavelengths and of the excitation spectrum of haematoporphyrin derivative in vitro suggested that green light might be more efficient than red in destroying thin tumours. Experimentally, we confirmed this for tumours up to approximately 1.2 mm thick, a depth exceeding that of most carcinomas-in-situ. The superiority of green light over red in terms of the illumination time required to produce equivalent depths of necrosis may extend to greater depths (3-4 mm) if the former is produced by an argon laser and the latter by an argon-pumped dye laser. The relation between depth of necrosis Zn and light dose D is shown to be Zn = sigma gamma-1 1n(D/theta gamma) where sigma gamma is the attenuation coefficient for light at wavelength gamma and theta gamma the threshold light dose for producing necrosis at that wavelength. This logarithmic relationship suggests that it may be difficult to eradicate large tumours merely by increasing the light dose, and indicates the need for other approaches.

Optical properties of human blood vessel wall and plaque.

Optical properties of blood vessel wall and plaque from human cadaver material are presented for the argon laser (514.5 nm), He-Ne laser (633 nm), and the Nd-YAG laser (1,060 nm) wavelengths. Measurements were performed with an integrating sphere arrangement and analyzed in terms of Kubelka-Munk absorption and scattering coefficients.

Boundary layer resistance of steady-state oxygen diffusion facilitated by a four-step chemical reaction with hemoglobin in solution.

The steady-state diffusion of oxygen in layers of hemoglobin solutions takes place under conditions of chemical equilibrium everywhere except in two boundary layers where deviations occur. The transport resistance of a boundary layer is defined in this paper. It is independent of the solution in the region of equilibrium and therefore forms a suitable basis to compare facilitated transport with different reaction schemes. Results are presented for a four-step reaction scheme between oxygen and hemoglobin, and compared with those of a single-step reaction for various reaction rates. The sensitivity of the results to changes in the reaction rates of the four-step model is also studied. With a knowledge of the boundary layer resistance the results of equilibrium calculations can be corrected in a simple way, which allows dirrect evaluation of experimental results.