Kevin D. Taylor

Large laser sheaths for pacing and defibrillator lead removal

In a recent clinical trial, the 12‐F laser sheath showed 95% success in completely explanting chronically implanted pacing leads smaller than 7.5‐F diameter. For larger leads, two new sizes of laser sheath have been implemented, the 14‐F and 16‐F (outer diameter) devices, which accommodate leads up to 9.5‐ and 11.5‐F, respectively. The object of this study was to determine the cutting ability of the larger devices compared to the 12‐F design.

Excimer-laser-assisted thrombolysis: the effect of laser fluence, repetition rate, and catheter size

The objective of this study was to evaluate the effect of laser fluence, repetition rate and catheter size on the ablation of thrombus by an excimer laser, in-vitro. Ablation of reconstituted thrombus was conducted with a XeCl (308 nm) excimer laser. Fluences of 30 and 45 mJ/mm2, repetition rates of 25 and 40 Hz, and catheters of sizes 0.9, 1.4, and 2.0 mm were used. Ablation efficiency (?g/J*pulse), and mass removal rate (?g/sec) were calculated by measuring the pre- and post-ablation weight of clot blocks (~2x1x1 cm3) placed on a precision scale. Depending on lasing parameters and catheter size, the ablation efficiency ranged from 0.51+/-0.09 to 1.13+/-0.20 ?g/J*pulse (N=12), while the mass removal rate ranged from 105+/-23 to 936+/-146 ?g/sec (N=12). Overall, there was a strong dependence of both quantities on the catheter size. Ablation efficiency was not significantly affected by either the fluence or the repetition rate, while mass removal rate increased with increased fluence and repetition rate. Excimer laser can effectively ablate thrombus in vitro. Catheter size affects both ablation efficiency and mass removal rate, while fluence and repetition rate mainly affect the mass removal rate.

Large eccentric laser angioplasty catheter

In response to recent demand for increased debulking of large diameter coronary vascular segments, a large eccentric catheter for excimer laser coronary angioplasty has been developed. The outer tip diameter is 2.0 mm and incorporates approximately 300 fibers of 50 micron diameter in a monorail- type percutaneous catheter. The basic function of the device is to ablate a coronary atherosclerotic lesion with 308 nm excimer laser pulses, while passing the tip of the catheter through the lesion. By employing multiple passes through the lesion, rotating the catheter 90 degrees after each pass, we expect to create luminal diameters close to 3 mm with this device. Design characteristics, in-vitro testing, and initial clinical experience is presented.

Particulate debris analysis during excimer laser thrombolysis: an in-vitro study

Laser assisted thrombolysis may be a viable alternative or adjunct to current thrombolytic therapies. However, knowledge of the particulate debris associated with this modality is limited. The objective of this in-vitro study was to evaluate and quantify the particulate generation following ablation of thrombus. Ablation of reconstituted thrombus was conducted in-vitro with an excimer laser operating at 308 nm and multifiber laser catheters. Particulate debris was quantified by weighing filtered particles and light obscuration particle counting. The effect of laser parameters, catheter size, and clot consistency on particulate production and ablation efficiency was investigated. For light obscuration particle counting experiments, the total number and size distribution of particles was similar for all laser parameters. More than 92% and 99% of the particulate generated was less than 10 and 25 microns, respectively. For the filtering experiments, particulate greater than 10 microns amounted for less than 6% of the original clot weight. Increased catheter size, increased laser parameters, and decreased clot consistency produced greater amounts ablated without increasing particulate debris production. The majority of particulate produced by excimer laser ablation of thrombus in-vitro was sub-cellular in size and debris production was not influenced by laser parameters, clot consistency, or catheter size.

Optimally spaced fiber catheter for excimer laser coronary angioplasty (ELCA)

Current multiple-optical-fiber catheters for excimer laser coronary angioplasty (ELCA) emit pulsed light at 308nm from a xenon chloride (XeCl) excimer laser to remove plaque in occluded arteries. Because the fiber ends, arranged in a closest- packed array, do not cover the entire surface of the catheter tip, these devices ablate holes typically holes typically 75-80 percent of the catheter tip diameter. To increase the ablation effectiveness, an optimally spaced fiber catheter has been designed in which the fiber-to-fiber spacing is increased precisely enough so as to cover the entire catheter tip area with fibers. In vitro and in vivo testing compared the optimally spaced catheter to catheter models currently in clinical use. Although device handling characteristics were found to be identical, the optimally spaced devices removed a significantly greater amount of tissue. This may offer a technical advantage in a clinical setting.

From Laser Physics to Clinical Utilization: Design and Ablative Properties of Cardiovascular Laser Catheters

Although the notion of excimer laser atherectomy (ELA) first appeared in the early 1980’s, almost 10 years passed before the technique became commercially available. As with many new technologies, improvements in the clinical application of ELA relied on the interplay among several technical disciplines. Understanding the biophysics of laser-tissue interaction, designing fiberoptic catheters that leveraged that understanding, and developing clinical technique required to use those catheters successfully, were required to advance the practice of ELA. That interplay created a relentless drive for improvement as challenges and disappointments were addressed with new understanding and updated catheter designs.

Excimer laser lead extraction catheter with increased laser parameters

A fiber optic catheter connected to a pulsed excimer laser (308 nm) is currently used to extract chronically implanted pacemaker and defibrillator leads at Fluence of 60 mJ/mm2 and repetition rate of 40 Hz. The object of this study was to determine the effect of higher repetition rates (80 Hz) in the catheters cutting performance. The penetration rate (micrometers /sec), and the associated mechanical and thermal effects were measured in soft (porcine myocardium) and hard tissue (bovine tendon) at 60 mJ/mm2-80 Hz, and were compared to the corresponding values at commercially available laser parameters (60 mJ/mm2-40 Hz). Ablation rates were measured with perforation experiments and the extent of thermal and mechanical damage was measured under polarized light microscopy. For hard (soft) tissue, the laser catheter demonstrated penetration speed of 106 +/- 32 (302 +/- 101) micrometers /sec at 40 Hz and 343 +/- 120 (830 +/- 364) micrometers /sec at 80 Hz. Maximum extent of thermal effects at 40 Hz and 80 Hz was 114 +/- 35 micrometers (72 +/- 18) and 233 +/- 63 micrometers (71 +/- 16) respectively. Maximum extent of mechanical effects at 40 Hz and 80 Hz was 188 +/- 63 micrometers (590 +/- 237) and 386 +/- 100 micrometers (767 +/- 160) respectively. In vitro testing of the laser catheter with 80 Hz laser parameters has demonstrated increased penetration speed in both soft and hard fibrous tissue, while maintaining associated thermal and mechanical effects within limited ranges.