Endocardial photoablation by excimer laser

A xenon-chlorine excimer laser was used to irradiate normal endocardium of fresh sheep and pig hearts as well as unfixed human endocardial scar. Forty pulses of 370 J and 35 ns each resulted in penetration of up to 12 mm in normal tissue and only 3.5 mm in scarred endocardium. Dosimetry indicated that the volume of vaporized scarred tissue was 1/10th that of normal endocardium (0.19 to 0.40 versus 1.35 to 3.22 mm3/J). Ultrastructurally, there was a sharp demarcation of only 10 mu between the region of injury and normal myocardium, with little evidence of heat injury. The high power and short duration of these lasers coupled with the lack of a boundary zone of injury suggest that excimers may be an ideal tool for arrhythmia ablation.     

Origin of arterial wall dissections induced by pulsed excimer and mid-infrared laser ablation in the pig.

To study adjacent tissue damage after delivery of holmium, thulium and excimer laser pulses, porcine thoracic aortas were irradiated in vivo. After 3 days, microscopic analysis of 67 craters produced by all three lasers demonstrated large dissections extending from the craters. The mean diameter of the dissections was smaller for excimer-induced craters (1.38 +/- 0.42 mm; n = 22) than for holmium-induced (2.7 +/- 0.87 mm; n = 22) and thulium-induced (2.37 +/- 0.42 mm; n = 14) craters (p less than 0.01 vs. mid-infrared dissections). In addition, microscopic analysis demonstrated necrosis adjacent to the crater. The lateral necrotic zones of the thulium-induced craters were smaller than the holmium- and excimer-induced necrotic zones (p less than 0.01). To identify the origin of the excessive tissue tearing, laser-saline and laser-tissue interaction were compared in vitro by time-resolved flash photography. In saline solution, the mid-infrared lasers showed bubble formation on a microsecond time scale. The excimer laser produced similar bubbles in the vicinity of tissue. For all three lasers, elevation of the tissue surface was shown during in vitro ablation. Dimension (diameter up to 4 mm) and time course (rise time of 100 to 300 microseconds) of bubble formation and tissue elevation were strikingly similar. Thus, tissue dissections are caused by the expansion of a vapor bubble within the target tissue. Coronary dissections after excimer and mid-infrared laser angioplasty might be related to the forceful bubble expansion.     

Initial angiographic results in ablation of atherosclerotic plaque by percutaneous coronary excimer laser angioplasty without subsequent balloon dilatation

Percutaneous transluminal coronary excimer laser angioplasty was performed in 15 patients using a 1.3-mm diameter laser catheter. The catheter consists of 20 concentric quartz fibers of 100 microns diameter each located around a central lumen suitable for a 0.014-inch flexible guidewire. The catheter was coupled to an excimer laser delivering energy at a wavelength of 308 nm and at a pulsewidth of 60 ns. Quantitative analysis of the angiograms documented a decrease from 77 +/- 15% diameter stenosis before intervention to 40 +/- 22% after the first irradiation cycle and to 21 +/- 17% after termination of laser ablation. The minimal lumen diameter increased from 0.4 +/- 0.2 to 1.3 +/- 0.4 and to 1.6 +/- 0.4 mm, respectively. Vessel reocclusion was seen in 2 patients at 24-hour control angiography. No procedure-related major complications such as vessel perforation occurred. In 8 patients, however, intraluminal lucencies were seen, which were persistently visualized 24 hours after intervention in 6 patients. Despite pretreatment with intracoronary nitroglycerin, coronary spasm occurred in 8 patients and was reversible after additional sublingual vasodilator therapy. The results of this pilot study suggest that percutaneous coronary excimer laser angioplasty is feasible and effective for ablation of coronary lesions in selected patients and can be performed without subsequent conventional balloon angioplasty. The clinical impact of this new interventional technique, however, remains to be assessed.     

Blunt atrial transseptal puncture using excimer laser in swine.

OBJECTIVES: We describe a new approach that may enhance safety of atrial transseptal puncture using a commercially available laser catheter that is capable of perforation only when energized. We test this approach in swine. BACKGROUND: Despite wide application, conventional needle transseptal puncture continues to risk inadvertent nontarget perforation and its consequences. METHODS: We used a commercial excimer laser catheter (0.9-mm Clirpath, Spectranetics). Perforation force was compared in vitro with a conventional Brockenbrough needle. Eight swine underwent laser transseptal puncture under X-ray fluoroscopy steered using a variety of delivery catheters. RESULTS: The 0.9-mm laser catheter traversed in vitro targets with reduced force compared with a Brockenbrough needle. In vitro, the laser catheter created holes that were 25-30% larger than the Brockenbrough needle. Laser puncture of the atrial septum was successful and accurate in all animals, evidenced by oximetry, pressure, angiography, and necropsy. The laser catheter was steered effectively using a modified Mullins introducer sheath and using two different deflectable guiding catheters. The mean procedure time was 15 +/- 6 min, with an average 3.0 +/- 0.8 sec of laser activation. There were no adverse sequelae after prolonged observation. Necropsy revealed discrete 0.9-mm holes in all septae. CONCLUSION: Laser puncture of the interatrial septum is feasible and safe in swine, using a blunt laser catheter that perforates tissues in a controlled fashion.     

Coronary endarterectomy using an excimer laser. Preliminary peroperative results

From experimental and clinical experience, safe coronary angioplasty cannot be performed with CW lasers. The excimer laser does present a number of advantages in vitro: non-thermal ablation of plaques and a linear relationship between the number of pulses and the depth of the crater, so that tissue ablation is quantitatively predictable. A 308 nm, 20 ns pulse duration, 1 to 5 repetition rate laser was specifically designed for clinical application. During cardiopulmonary bypass prior to bypass grafting in 10 symptomatic patients, a 1 mm diameter core UV-tipped fiberoptic was introduced via the coronary arteriotomy and directed in contact with the coronary stenosis. Laser power was progressively increased until the stenosis or occlusion was recanalized. The quality of this angioplasty was controlled by calibration of he neo-lumen, cardioplegia solution flow through the lased segment, and 8th day coronary angiography. The laser treated coronary segments of the first 4 patients showed clearly parallel-lined patent neo-lumen despite competitive bypass graft flow. The main limitation of the method is that laser coronary recanalization is confined to the fiber core diameter. The authors conclude that: 1) excimer laser angioplasty is a safe and efficient intra-operative procedure; 2) the most critical problem for percutaneous laser angioplasty remains flexibility of the apparatus as the fiber diameter must be large enough to provide an adequate arterial neo-lumen.     

准分子激光和紫外线照射对胰岛免疫原性的影响

新生大鼠胰岛样细胞团经准分子激光和中波紫外线照射处理后，其免疫原性明显降低，激光组尤为显著，形态学检查示胰岛细胞分泌颗粒和亚细胞结构保持完整无损。胰岛素分泌功能与对照组无显著性差异。经ＳＴＺ引致糖尿在鼠中胰岛异体移植，结果表明激光组受体大鼠糖尿缓解时间较紫外线组与对照组明显处宅。     

Laparoscopic treatment of liver tumours using a two-needle probe bipolar radiofrequency ablation device

BackgroundMany hepatobiliary centres are increasingly utilizing thermocoagulative devices such as bipolar-radiofrequency ablation (B-RFA). Compared with monopolar-radiofrequency ablation (M-RFA), B-RFA does not require grounding pads, thereby avoiding dermal burn injuries, and does not position probes directly into the tumour but rather on the perimeter. Additionally, B-RFA can precoagulate parenchyma to assist in hepatic resection. Herein, we report our early experience using B-RFA.MethodsA retrospective review identified 68 patients who underwent M-RFA or B-RFA between June 2004 and September 2010 in an academic centre. Peri-operative metrics were analysed.ResultsM-RFA was used to treat 30 patients, whereas B-RFA was used for 17 patients. There were no differences in peri-operative metrics, survival or disease recurrence between M-RFA and B-RFA. Seventeen additional patients underwent B-RFA precoagulation during laparoscopic resection (segmentectomy in eleven patients and multi-segmental resection in six patients). Four patients with multifocal disease underwent procedures that combined B-RFA with resection.ConclusionsThe early experience utilizing B-RFA demonstrates equivalency to M-RFA with respect to peri-operative metrics and survival. Moreover, B-RFA can be utilized to precoagulate tissue during a planned resection, making it not only a useful tool for tumour therapy but also a useful adjunct during surgical resections.     

准分子激光消蚀联合药物涂层球囊治疗股腘动脉支架内再狭窄的临床疗效

目的评价准分子激光消蚀联合药物涂层球囊治疗股腘动脉支架内再狭窄的安全性和有效性。方法选择2016年11月～2018年12月在我中心接受准分子激光联合药物涂层球囊治疗股腘动脉支架内再狭窄的患者13例,男11例,女2例,平均年龄(71.46±9.23)岁,平均病程(9.2±4.0)个月。回顾性分析患者病变、围术期及手术前后临床症状改善等临床资料,患者术后1、3、6、12、18和24个月定期随访,采用Kaplan-Meier生存分析计算一期通畅率。结果 13例患者均完成定期随访,平均随访时间(8.62±8.27)个月,手术成功率100%,无穿刺点血肿及围术期死亡患者。13例患者术后临床症状均较术前改善,7例跛行患者跛行距离较术前增长50～500m,3例静息痛患者静息痛消失,术后踝肱指数较术前明显增加(0.81±0.15 vs 0.40±0.30,P0.05)。Kaplan-Meier生存分析计算一期通畅率显示,患者3和6个月的一期通畅率分别为92.3%和83.1%。结论准分子激光消蚀联合药物涂层球囊治疗股腘动脉支架内再狭窄的安全性及近中期疗效尚可,但仍需扩大样本量随访观察远期效果。     

Tissue ablation with excimer laser and multiple fiber catheters: effects of optical fiber density and fluence

This study was performed to assess the ablational properties of 1.4-, 1.7-, and 2.0-mm wire-guided multiple fiber catheters coupled to a XeCl excimer laser. Samples of postmortem human aorta were irradiated in blood at fluences of 40, 50, and 60 mJ/mm 2. Our results indicate that: 1) an increase in the active irradiation coverage results in an increase in the ablation efficiency; 2) the ablation efficiency is not fluence related using the 1.4- or 1.7-mm multiple fiber catheter but efficiency is fluence dependent using the 2.0-mm multiple fiber catheter; 3) the depth of tissue ablated with a multiple fiber catheter depends primarily upon the proportion of the active irradiation coverage at the catheter tip; 4) the 2.0-mm multiple fiber catheter induces craters surrounded by a larger zone of tissue damage than that observed with the 1.4- or 1.7-mm multiple fiber catheter; and 5) the 2.0-mm multiple fiber catheter should be used cautiously for laser angioplasty because of its high penetration and its risk of arterial wall damage.     

Selective ablation of atheromas using a flashlamp-excited dye laser at 465 nm.

Ablation of human atheromas with laser pulses that had only a small effect on normal artery tissue was shown in vitro in air and under saline using 1-mu sec pulses at 465 nm from a flashlamp-excited dye laser. At this wavelength, there is preferential absorption in atheromas due to carotenoids. The threshold fluence for ablation was 6.8 +/- 2.0 J/cm2 for atheromas and 15.9 +/- 2.2 J/cm2 for normal aorta tissue. At a fluence of 18 J/cm2 per pulse, the ablated mass per unit of energy ranged from 161 to 370 micrograms/J for atheromas and from 50 to 74 micrograms/J for normal aorta tissue. Ablation products consisted of cholesterol crystals, shredded collagen fibers, and small bits of calcific material. Most debris was less than 100 micron in diameter, but a few pieces were as large as 300 micron. High-speed photography of ablation in air suggested explosive ejection of debris, caused by vapor formation, at speeds on the scale of 300 m/sec. Histological analysis showed minimal thermal damage to residual tissue. These data indicate that selective laser ablation of atheromas is possible in vitro.     

Pulmonary vein isolation using a compliant endoscopic laser balloon ablation system in a swine model

Introduction  

The incidence of pulmonary vein reconnection and recurrent atrial fibrillation after a single catheter ablation procedure is unacceptably high. We studied the ability of a novel endoscopic laser balloon ablation system (EAS) to achieve acute and chronic pulmonary vein (PV) isolation in a swine model.     

Canine tracheal injury by neodymium-YAG laser irradiation

The relationship between endoscopic graded neodymiumyittrium aluminum garnet (Nd-YAG) laser intensity and the magnitude of effects on the tracheal wall was studied in two mongrel dogs. The dogs were anesthetized and graded Nd-YAG laser burns of 50, 100, and 200 Joules (J) were produced on the distal tracheal walls with a laser fiber inserted through a bronchoscope. One dog was killed immediately after injury and the other 24 hours later. At the time of killing, the trachea was excised and prepared for light microscopic (LM) and scanning electron microscopic (SEM) examination. We found that the injury produced by the 50 J intensity beam was confined to the mucosa and submucosa, with no destruction of the tracheal cartilage; by contrast, transmural penetration of the trachea was observed at intensities of 100 and 200 J. These results indicate that a strong correlation exists between laser intensity and the magnitude of the resulting tracheal injury. We suggest that the intensity of a Nd-YAG laser, endoscopically directed perpendicular to the tracheal wall, should not exceed 50 J in order to minimize the risk of perforating the tracheal wall.     

Photodynamic ablation of early cancers of the stomach by means of mTHPC and laser irradiation: preliminary clinical experience

Background—Radical surgicaltreatment has been the first choice for early gastric cancer, but highresolution endosonography allows in situ diagnosis with a highsensitivity and specifity and in consequence the option of localendoscopic treatment.
Aims—To evaluate photodynamictherapy (PDT) usingmeso-tetrahydroxyphenylchlorin (mTHPC)as the photosensitiser in superficial gastric cancer.
Methods—Twenty two patients withsuperficial early gastric cancer received mTHPC (0.075 mg/kgintravenously) and were treated 96 hours later with red light at 652 nm(20 J/cm²). Tumour response was assessed by endoscopy andextensive biopsy.
Results—Endoscopies performed twoto three days after PDT showed a haemorrhagic fibrinoid necrosis of themucosal layer. Complete remission was achieved in 16/22 (73%)patients: 13/16 (80%) with intestinal type cancer and 3/6 (50%) witha diffuse Lauren's carcinoma. The mean follow up period was 12 monthsand 20 months, respectively. An average of 1.8 treatment sessions wasrequired. Severe side effects were not observed. Seven patients hadmild to moderate skin photosensivity reactions; 12 had local pain afterPDT for 1-10 days.
Conclusion—PDT using mTHPC as thephotosensitiser represents a safe and efficient method for topicaltreatment of early gastric cancer, especially of Lauren's intestinalcarcinoma. If the preliminary results can be verified in larger patientseries and during long term follow up, local treatment of early cancersof the stomach by PDT could be considered as a therapeutic option forselected patients.

Keywords:photodynamic therapy; early gastric cancer; localendoscopic therapy

     

Simple percutaneous coronary interventions using the modification of complex coronary lesion with excimer laser

Excimer laser coronary atherectomy (ELCA), a unique percutaneous coronary intervention (PCI) device, comprises a monorail-type system and is compatible with any standard 0.014-inch guidewire. ELCA is the only device that vaporizes the atherosclerotic plaques or modifies underlying plaque located underneath to a hard tissue, such as severe calcification or a stent. Therefore, ELCA differs from other coronary atherectomy devices and is useful for patients with acute coronary syndrome, chronic total occlusion or under-expanded stents. This case series reports on patients treated using ELCA to simplify complex PCI procedures. Furthermore, we review and discuss ELCA in several situations.     

Percutaneous angioscopic evaluation of luminal changes induced by excimer laser angioplasty.

Angioscopy has been shown to provide more detailed information on lesion morphology before and after interventional procedures than angiography. Therefore to evaluate the effects of laser angioplasty, angioscopy was performed in five patients with peripheral or coronary vascular disease who underwent excimer laser angioplasty. The excimer laser was operated at 308 nm, 135 nsec, 25 Hz, and 40 to 60 mjoules/mm2 and was coupled into multifiber wire-guided catheters of 1.4 to 2.0 mm diameter for coronary lesions and into catheters of 2.2 mm diameter for peripheral lesions. There were three coronary (one left anterior descending, one circumflex, one right coronary artery) and two peripheral (one common iliac artery, one superficial femoral artery) lesions. Angioscopy was successfully performed before and after laser ablation without any complications in all five lesions. The characteristics of angioscopic findings after excimer laser angioplasty consisted of flaps, fractures of plaques, and abundant tissue remnants. There was no apparent thermal injury. Recanalized channels were small and irregular. These results indicate that (1) angioscopy is effective and safe for evaluation of lesion morphology after laser angioplasty; (2) laser ablation does not result in thermal injury; and (3) irregular channels after recanalization and abundant tissue remnants may explain the suboptimal results after laser angioplasty.     

Altered lymphocyte proliferation by low dosage laser irradiation

The effect of gallium-aluminum-arsenide laser irradiation on the proliferation of human lymphocytes in culture in response to mitogenic stimulation by phytohemagglutinin was investigated. Mitogenic proliferation was inhibited by the laser irradiation at a low energy fluence and enhanced at a high energy fluence. The results indicate that low-watt laser irradiation can interfere with the immune response in vitro, and similar interference could occur in patients with rheumatoid arthritis subjected to laser therapy, if an appropriate dosage is chosen.