Experimental and clinical studies of using Nd: YAG laser via domestic metal cap and sapphire tip delivery systems

Sixteen segments of normal human cadaver aorta were irradiated by Nd: YAG laser beam delivered via domestic metal cap and sapphire tip fiber systems. Results revealed that the adherence to target tissue and tissue damage were more apparent with metal caps than those with sapphire tips. Furthermore, the latter had smoother edges of ablation crater less carbonization layers and smaller thermal necrotic zones. The delivery systems were used to perform laser angioplasty in 2 iliac and 5 coronary atherosclerotic arteries and all achieved immediate recanalization.     

Electrical thermal angioplasty: catheter design features, in vitro tissue ablation studies and in vivo experimental findings

A prototype electrical thermal tip catheter has been developed for ablation of atherosclerotic plaques. The operating principle is based on establishing an electric arc between a central electrode and the inside of an enclosing metallic tip to convert electrical energy to thermal energy. The metal tip catheter can be heated rapidly and boils water in a saline bath with less than 1 W of power. In vitro studies, using human atherosclerotic aortic segments, demonstrated that effective tissue ablation required more power in saline than in air (more than 9 W vs less than 1 W). The rate of tissue ablation varied with the amount of power delivered and the catheter tip pressure against tissue. In a saline field, 2-mm thickness aortic wall segments were consistently perforated in 3 seconds when 15 W of power and 20 g/mm2 of pressure were applied. Using an atherosclerotic rabbit, in vivo electrical thermal angioplasty (3 W of power for 10-second treatment sequences) was performed in obstructed iliofemoral vessels after mechanical recanalization was attempted. Of the 7 vessels that were more than 50% narrowed (compared with contiguous normal vessel diameter), mechanical recanalization was effective in only 1, but thermal angioplasty resulting in an increased lumen diameter was successful in 6 others. The recanalized segments were 8 to 10 cm; gross morphologic and histologic examination of recanalized vessels demonstrated little or no thermal injury. In addition, significant cholesterol-laden plaques remained in the vessel lumen, which appeared to have been compressed and displaced laterally.(ABSTRACT TRUNCATED AT 250 WORDS)     

Transcatheter laser dissolution of human atherosclerotic plaques: a model for testing catheters and techniques

We constructed a model of the human arterial circulation that can be used to test laser angioplasty catheters and techniques on obstructed human coronary arteries under simulated physiologic conditions of blood pressure and flow. In this model system, a balloon-tipped catheter with a central, 0.02-cm light fiber was used to deliver 4 W of laser energy to two obstructed human cadaver coronary artery segments and four normal dog femoral artery segments. Flushing the catheter with saline during the lases minimized lateral thermal tissue damage. Channels were created in the obstructed arteries that were twice the diameter of the light fiber used to lase. One of four dog arteries perforated, underscoring the potential hazards of the procedure and the need for laser catheters that are flexible and capable of precise alignment.     

Ultrasonic energy. Effects on vascular function and integrity

BACKGROUND. Ultrasonic energy transmitted via flexible wire probes provides a new means of ablating atherosclerotic plaque. We studied the effects of ultrasonic energy (20 kHz) delivered via a ball-tipped wire probe on arterial vasomotor behavior in rabbit thoracic aortas in a perfused whole-vessel model. METHODS AND RESULTS. After precontraction with phenylephrine (10(-5) M) or KCl (60 mM), the effects of ultrasonic energy (0.7-5.5 W x 60 seconds, 42-330 J) on arterial vasomotor behavior were measured using long-axis ultrasonic vessel imaging of the proximal (ultrasonic probe-treated) and distal (untreated) control segments. The efficacy of plaque ablation at these same probe-tip power outputs was evaluated in atherosclerotic, human cadaver iliofemoral arteries. Ultrasonic energy caused dose (energy)-dependent relaxation in rabbit aortas after precontraction with phenylephrine in arteries with endothelium (n = 8) and without endothelium (n = 8) (p less than 0.001 versus ultrasound treated at power outputs of 2.9 and 5.5 W). There was no difference in the relaxation dose responses between endothelialized and endothelially denuded segments (p = NS). Ultrasonic energy also caused significant relaxation (67 +/- 8%) after voltage-dependent precontraction with 60 mM KCl. Temperature measurements revealed less than 1 degrees C warming of the vessel wall during as long as 2 minutes of treatment at a power output of 5.5 W. Pathological examination showed no smooth muscle injury at (moderate) power outputs that caused arterial relaxation. At probe-tip power outputs of 2.9-5.5 W, ultrasonic energy recanalized two of two totally occluded cadaveric iliofemoral vessel segments. The ultrasonic ablation catheter was also demonstrated to cause arterial relaxation in a recanalized canine femoral artery in vivo. CONCLUSIONS. Ultrasonic energy delivered via a flexible-wire probe produces dose-dependent, endothelium-independent smooth muscle relaxation capable of reversing both receptor-mediated and voltage-dependent vasoconstriction in vitro. At moderate power outputs, this relaxation response does not appear to be due to thermal effects or irreversible smooth muscle cell injury. This vasorelaxant effect of ultrasonic energy is also apparent in vivo, at doses that effectively ablate atherosclerotic plaque, and may improve the safety of arterial recanalization using ultrasonic energy.     

Short- and long-term effects of transcatheter ablation of the coronary sinus by radiofrequency energy

Catheter ablation of left-sided atrioventricular accessory pathways through the coronary sinus by direct-current shock may be complicated by rupture and thrombosis of the coronary sinus and injury to the coronary arteries. This study examined short and long-term effects of radiofrequency catheter ablation of the coronary sinus in 20 closed-chest dogs to determine whether this technique is feasible for potential interruption of left-sided accessory pathways. Single-pulsed radiofrequency energy (750 kHz, 85-293 J) was delivered to three sites in the distal and middle coronary sinus between the distal (1) or the proximal electrodes (2 or 3) of a standard 6 French quadripolar catheter and a chest-wall patch electrode. Single-pulsed radiofrequency energy (78-293 J) was also applied to two sites near the ostium of the coronary sinus with the proximal (4) or the distal (1) electrode of the same catheter. Coronary artery and levophase coronary sinus angiograms obtained before and immediately after ablation, as well as before killing, showed intact vascular structures in all dogs. Right atrial, pulmonary arterial, and aortic pressures measured in three dogs did not change significantly at the time of energy delivery. No significant changes were found in atrioventricular nodal refractoriness and conduction. None of the dogs had significant rhythm disturbances during and after ablation as evaluated by ambulatory electrocardiographic monitoring and periodic rhythm strips at follow-up. Ten dogs were killed 1-7 days after ablation, three dogs were killed at 4 weeks, three dogs at 6 weeks, two dogs at 8 weeks, and two dogs at 12 weeks. Discrete lesions ranging in size from 3 x 3 to 8 x 10 mm2 in surface area and 0.5-4.5 mm in depth were found in the coronary sinus with most of the lesions extending to the left atrial and left ventricular myocardium. There was neither rupture of the coronary sinus nor occlusion of the coronary arteries. Mural thrombus was found in the coronary sinus on five acute lesions in two dogs, but none was noted on the chronic lesions, which was characterized by chronic granulation tissue and fibrosis. Two dogs in the study during chronic conditions had damage to branches of the underlying coronary artery that showed necrotizing arteritis and arterial sclerosis. Conduction system studies in four dogs showed some chronic inflammatory and fibrotic changes. Similar discrete lesions were found in situ in the coronary sinus of four postmortem human hearts with radiofrequency catheter ablation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Thermal compression and molding of atherosclerotic vascular tissue with use of radiofrequency energy: implications for radiofrequency balloon angioplasty

The combined delivery of pressure and thermal energy may effectively remodel intraluminal atherosclerotic plaque and fuse intimal tears. To test these hypotheses with use of a non-laser thermal energy source, radiofrequency energy was delivered to postmortem human atherosclerotic vessels from a metal "hot-tip" catheter, block-mounted bipolar electrodes and from a prototype radiofrequency balloon catheter. Sixty-two radiofrequency doses delivered from a metal electrode tip produced dose-dependent ablation of atherosclerotic plaque, ranging from clean and shallow craters with histologic evidence of thermal compression at doses less than 40 J to tissue charring and vaporization at higher (greater than 80 J) doses. Lesion dimensions ranged between 3.14 and 3.79 mm in diameter and 0.20 and 0.47 mm in depth. Tissue perforation was not observed. To test the potential for radiofrequency fusion of intimal tears, 5 atm of pressure and 200 J radiofrequency energy were delivered from block-mounted bipolar electrodes to 48 segments of human atherosclerotic aorta, which had been manually separated into intima-media and media-adventitial layers. Significantly stronger tissue fusion resulted (28.5 +/- 3.3 g) with radiofrequency compared with that with pressure alone (4.8 +/- 0.26 g; p less than 0.0001). A prototype radiofrequency balloon catheter was used to deliver 3 atm of balloon pressure with or without 200 J radiofrequency energy to 20 postmortem human atherosclerotic arterial segments. In 10 of 10 radiofrequency-treated vessels, thermal "molding" of both normal and atherosclerotic vessel wall segments resulted with increased luminal diameter and histologic evidence of medial myocyte damage.(ABSTRACT TRUNCATED AT 250 WORDS)     

Transluminal laser irradiation of coronary arteries in live dogs: an angiographic and morphologic study of acute effects

In vivo coronary transluminal laser irradiation, using energies known to vaporize atherosclerotic plaques and thrombi, was performed in normal coronary arteries of 5 anesthetized mongrel dogs. A 200-mu core silica optical fiber with a radiopaque tip was advanced through a catheter to either the left anterior descending or circumflex coronary arteries. Coronary artery perforation occurred during manipulation of the fiber in 1 dog. In 4 dogs, argon laser radiation was delivered at 1-second intervals. A total of 45 different sites were irradiated in 8 coronary arteries. In 5 of these arteries 1 W was used and in the 3 other arteries 2 W were used. Coronary angiography showed perforation of 5 of these 8 arteries. Two arteries were perforated using 1 W and 3 using 2 W. Within 30 minutes, 3 dogs with perforation died of cardiac tamponade. In all 4 dogs postmortem examination showed perivascular blood extravasation around all 8 lased coronary arteries. Transluminal lasing of normal dog coronary arteries using delivery systems and energies similar to those known to vaporize atherosclerotic plaques and thrombi resulted in arterial perforation, frequently followed by cardiac tamponade.     

Experimental studies on coronary laser angioplasty

To establish the method of coronary laser angioplasty using the argon laser, we investigated the optimal condition of laser ablation and the relationship between the size of laser probe and the diameter of the vessel. First, the relationship between laser energy and tissue reaction to the laser was examined using human cadaveric arteries. Subsequently, we recognized that repeated laser ablation is the optimal method with each shot being limited to 5 10 watts (W) in output and 2 seconds of ablation time when using a metal tip probe (MTP) of 1.5 mm in diameter. According to the experimental condition described above, we examined the response of normal coronary arteries to the laser in vivo. If the size of MTP was not suitable for the diameter of the vessel, thermal constriction of the coronary artery was observed; MTP/vessel diameter ratio should be 0.7 or less to avoid vessel constriction by thermal damage from the laser. Neither perforation nor spasm of the coronary artery was found in this experiment. In addition, the ablated area on the coronary artery was healed completely without thrombus formation and coronary stenosis, and it was covered with new endothelium 8 weeks after laser thermal ablation.     

The excimer laser: gross, light microscopic and ultrastructural analysis of potential advantages for use in laser therapy of cardiovascular disease

Excimer lasers are pulsed gas lasers that use a mixture of a rare gas and halogen as the active medium to generate pulses of short wavelength, high energy ultraviolet light. A krypton-fluoride gas mixture was used to achieve an excimer emission at a wavelength of 248 nm. A total of 30 atherosclerotic coronary artery segments were irradiated over a range of pulse energies (250 to 750 mJ), repetition rates (2 to 25 Hz), average powers (1.9 to 18.8 watts) and cumulative exposures (3 to 12 seconds). In no case was there gross, light microscopic or ultrastructural evidence of the pathologic injury typically associated with continuous wave laser irradiation of coronary artery segments. Similar results were achieved after excimer laser irradiation of 30 samples of myocardium. Excimer irradiation of calcified aortic valve leaflets accomplished focal debridement without pathologic tissue injury; when total debridement was attempted, however, gross charring was observed. The paucity of pathologic alterations observed after excimer irradiation of cardiovascular tissue may prove beneficial in precisely controlling laser ablation of pathologic tissue without injury to the surrounding normal tissue. Clinical application of excimer laser irradiation requires resolution of several issues, including the development of suitable fiber optics and laser coupling, evaluation of potential ultraviolet toxicity, and demonstration that ultraviolet light can be transmitted through a blood-filled system.     

Cooled tip ablation of left ventricular outflow tract tachycardia through the aortic sinus of valsalva

BACKGROUND: Monomorphic tachycardia with an epicardial site of the arrhythmic focus in the left ventricular outflow tract (LVOT) usually cannot be ablated by an endocardial approach. We describe the use of cooled tip catheter ablation through the aortic sinus of valsalva to treat LVOT tachycardia. METHODS: In seven patients (four males, one with valvular cardiomyopathy, six patients without heart disease) with sustained and non-sustained ventricular tachycardia (VT) an epicardial focus of LVOT tachycardia could be identified by pace-mapping and earliest local activation within the aortic sinus of valsalva. Coronary angiography served to define the position of the coronary arteries with respect to the ablation catheter. High frequency current was delivered using a closed-loop cooled tip catheter system (Chilli Cool(R), Boston Scientific). ECG, Holter-ECG, echocardiography and transesophageal echocardiography were performed after the procedure and 3 months later. RESULTS: Foci were located in the left (two patients), in the right (three) and in the a coronary aortic sinus (two). Successful ablation could be achieved in six patients. No procedure-related complications could be observed during a mean follow-up of 4.2 months. CONCLUSION: Monomorphic VT with epicardial origin in the LVOT can be successfully treated by cooled tip ablation through the aortic sinus of valsalva. The use of a cooled tip ablation system may be favourable in several ways: 1) it allows the creation of deep lesions necessary to reach remote foci; 2) due to lower temperatures at the catheter/tissue interface surface tissue damage may be reduced; 3) lower catheter temperature may additionally reduce the risk of local clot formation which is crucial for all left-sided procedures and especially for ablation in the sinus of valsalva.     

Effects of carbon dioxide, Nd-YAG, and argon laser radiation on coronary atheromatous plaques

Laser radiation has been successfully applied in several areas of medical practice. However, its use in cardiology and specifically its effects on obstructive atherosclerosis have largely been unexplored. To evaluate effects of laser radiation on atherosclerotic plaques 25 fresh necropsy atherosclerotic coronary artery segments were exposed to laser radiation with either a carbon dioxide, Nd-YAG, or argon laser. Split or intact segments were prepared under dry conditions or while immersed in saline solution or blood and exposed to laser radiation as power and duration of exposure varied. All 3 lasers were capable of creating controlled injury to atherosclerotic plaques. In general, the magnitude of injury varied according to the total energy delivered (that is, power times duration of exposure). Calcified and noncalcified plaques were penetrated with similar levels of injury. Histologic examination demonstrated that laser radiation produced a wedge incision in the atherosclerotic plaque which was surrounded by zones of thermal and acoustic injury.     

Plaque ablation by excimer laser irradiation using a movable energy-transmitting device

During the past 2 years, excimer laser energy has been shown to provide a highly suitable type of atherosclerotic plaque ablation, especially in small-diameter vessels such as coronary or crural arteries. Nevertheless, transmission of far-ultraviolet pulsed laser power has remained a major problem in animal studies and clinical trials. In an attempt to solve this problem, we constructed an energy-transmitting device for use with a Lambdaphysics EMG 102 excimer laser. The transmission system, which was housed in a rigid articulated arm, allowed movement in all directions and rotation along the long axis, thus permitting easy handling and guiding of the laser beam in the operating field. To test whether this device could deliver enough energy to remove atherosclerotic plaques within a period that would meet the requirements for intraoperative use, we obtained fresh human cadaver coronary arteries both with and without atherosclerotic disease, and irradiated them vertically and coaxially. A power meter was used to determine the effective amount of energy delivered at the distal end of each vessel. Energy densities up to 3 J/cm(2)/pulse were obtained, owing to energy focussing within the transmitting device. At 5 Hertz (Hz), tissue ablation consisted of approximately 20 microm/pulse. Areas of normal vascular tissue, as well as fibrohyalinous and lipid plaque components, were promptly ablated. Macroscopically, the "lasered holes" appeared well-circumscribed, with clear-cut surfaces and no carbonization. Light microscopy revealed no thermal damage to the boundary tissue. With this new energy-transmitting device, the surgeon can use excimer laser irradiation intraoperatively. There is no significant loss of energy between the generator and the tip, and energy densities of 3 J/cm(2)/pulse are available for sufficient plaque removal.     

Laser probe ablation of normal and atherosclerotic human aorta in vitro: a first thermographic and histologic analysis

The metal-tipped optical fiber or "laser probe" has been extensively studied in animal preparations in vivo and in human clinical trials of revascularization. The aim of this study was to evaluate the thermal characteristics of laser probe tissue ablation and to contrast the vascular tissue response to exposure to the laser probe and bare optical fiber. A 2 mm laser probe was heated with up to 4 W of argon-ion laser irradiation and applied to six postmortem strips of human nonatherosclerotic aorta as well as to five atherosclerotic aortic specimens. Surface temperature maps of the laser probe and of the vascular tissue in air were obtained via 8 to 12 micron thermographic imaging. Laser probe temperature was additionally monitored via thermocouples. Two strips each of normal and diseased aorta were irradiated directly with the bare optical fiber. Thus a total of 43 laser probe application sites and 19 bare fiberoptic laser irradiation sites on a total of 15 aortic strips were analyzed both thermographically and histologically. Based on measured temperature rises and histologic findings, the following observations were made: (1) The laser probe heats initially at its tip and attains a uniform surface temperature distribution within 5 sec. The steady-state temperature attained by the probe is inversely related to the thermal conductivity of the surrounding media. In all media studied, probe temperature increases linearly with applied laser energy. (2) Tissue ablation starts at temperatures greater than 100 degrees C, and ablation temperatures typically exceed 180 degrees C. Adventitial temperatures during laser probe application may reach 70 degrees C. Tissue ablation is enhanced both by greater laser energy deposition in the probe and by higher force at which the probe is applied to tissue. (3) Ablation of fibrofatty atheromata is more extensive than of nonatherosclerotic aortic tissue. This may be due to the lower thermal conductivity of atheromatous tissue. (4) In contrast to direct argon-ion laser ablation of aortic tissue, laser probe-mediated ablation occurs in a controlled fashion, is not associated with extensive subintimal dissections, and allows uniform conduction of heat to tissue as reflected by essentially "isothermal" injury lines.     

Imaging of post-mortem coronary arteries by 30 MHz intravascular ultrasound

Intravascular ultrasound cross-sectional imaging of the atherosclerotic artery may be employed to guide plaque ablation by spark erosion, atherectomy, laser irradiation or other means. To assess whether in the coronary artery the echolucent zone of the three-layered ultrasound appearance of muscular arteries might be a reliable boundary to halt transluminal ablative angioplasty, epicardial coronary arteries were scanned under pressure over a distance of 4–8 cm at 1 mm intervals. A 5.2F catheter with a 30 MHz transducer rotating at 600 RPM was used. In 419 images from four post-mortem hearts, aged at death 22, 31, 56 and 82 years, the presence of a distinct echolucent zone was scored as percentage of the wall circumference. The median scores were 0%, 0%, 10% and 75%, respectively. In the three youngest hearts, the three-layered appearance was largely absent. In the 82 year old heart, in contrast, the three-layered appearance could generally be identified. Within subjects, the presence of an echolucent zone was variable in location. Qualitatively, neither abundant medial elastin tissue nor a reduced medial thickness could explain the absence of an echolucent zone when the ultrasound image was compared to the corresponding microscopic section.The results show that in the 82 year old heart, 30 MHz intravascular ultrasound discrimination of coronary wall layers would be adequate to guide transluminal plaque ablation. In the younger hearts, guided ablation would fail due to the limited presence of a distinct echolucent zone as an ultrasound landmark of the media. Whether the presence or absence of an echolucent zone is related to age remains to be determined.     

有创中心动脉压与外周动脉压差及其与冠状动脉病变程度的关系

目的观察中心动脉压与外周动脉压之间的差异及其与冠状动脉粥样硬化病变程度之间的关系。方法选取同期行冠状动脉造影的患者322例,其中男218例,女104例,年龄40～82（59．61±9．01）岁。冠状动脉造影时同时测定中心动脉压及外周动脉压,根据冠状动脉造影结果对冠状动脉病变严重程度进行分组。观察各组间中心-外周脉压之间的差值（简称中-夕r脉压差）同冠状动脉粥样硬化病变程度之间的关系。结果冠心病组中-外脉压差明显高于非冠心病组[（29．47±16．71）mmHg比（19．97±7．99）mmHg,P〈0．05]。在冠状动脉狭窄程度、冠状动脉病变支数、冠状动脉Gensini积分的分组中,随着冠状动脉粥样硬化程度的增加,中-外脉压差增大,各组两两间比较差异均有统计学意义（P〈0．05）。结论中-外脉压差同冠状动脉粥样硬化病变程度有明显的相关性,可预测冠状动脉粥样硬化病变的程度。     

Protection of the coronary arteries during epicardial radiofrequency ablation with intracoronary chilled saline irrigation: assessment in an in vitro model

INTRODUCTION: The coronary arteries can be damaged during epicardial radiofrequency ablation (RFA) procedures. We hypothesized that intracoronary irrigation with chilled saline may be a useful technique for minimizing heat-induced damage to the coronary artery endothelium during this procedure. METHODS AND RESULTS: Twenty-nine ablation procedures were performed on 17 freshly excised ovine hearts. Radiofrequency current was delivered through an internally cooled, 4-mm-tip ablation catheter placed directly over the coronary artery (24 applications) and over noncoronary epicardium (5 applications). An Amplatz coronary catheter was used to internally irrigate the coronary artery with either 37 degrees C or 5 degrees C 0.9% saline (12 ablations each group). Fluroptic temperature probes were placed within the artery lumen under the ablation site and 15 mm distal from the ablation site. The peak intracoronary temperature directly under the ablation catheter was significantly lower (P = 0.001) in the chilled than in the nonchilled saline irrigation group (23.6 degrees C, interquartile range [IQR] 15.7-39.8 vs 54.6 degrees C, IQR 48.9-58.6). Blue tetrazolium stained lesion sections showed that the median distance between the ablation lesion and the artery wall was significantly higher (P = 0.004) for the chilled versus the nonchilled saline irrigation group (0.42 mm, IQR 0.25-0.70 vs 0.00 mm, IQR 0.00-0.28). CONCLUSIONS: Intracoronary irrigation with chilled saline may protect the coronary artery endothelium from heat-induced damage during epicardial RFA.     

通过动物实验评价射频能量对冠状动脉的急性损伤

目的通过动物实验观察射频消融术(RFCA)是否会导致冠状动脉(简称冠脉)的急性损伤,对比不同的消融方法对冠脉的影响。方法取成年犬21只,雌雄不限,随机分三组,第一组消融电极为4mm,能量级别设定为60℃/120s,分别消融左房室环、右房室环、冠状静脉窦内和心外膜的近冠脉处;第二组能量级别设定为80℃/120s,分别消融除心外膜外的其它三处;第三组消融电极为8mm,能量级别设定为60℃/120s,仅消融左右房室环。术毕观察消融点附近冠脉损伤情况,并取消融点及附近冠脉作病理检查,光镜下观察心肌和冠脉的变化。结果大体下观察,没有发现冠脉管腔的狭窄及管腔内血栓形成。对63处消融点附近的冠脉进行光镜检查时,3例冠脉或其分支出现明显变化,动脉壁破裂、壁结构消失、平滑肌溃疡、变性坏死,溃疡内有大量白细胞浸润;9例冠脉内皮细胞出现肿胀、脱落甚至消失;其余冠脉未有任何变化。结论常规RFCA是安全可靠的,但特殊部位、高能量射频消融时,应注意冠脉的损伤。     

Laser angioplasty and laser-induced thrombolysis in revascularization of anomalous coronary arteries

Acute coronary syndromes such as unstable angina and myocardial infarction are attributed to a pathophysiologic process that involves rupture of atherosclerotic plaque and subsequent thrombosis. Percutaneous intervention of anomalous coronary arteries in patients who present with acute coronary syndromes impose unique technical challenges related to the specific anatomic course and morphology of these vessels. Selection of appropriate guiding catheter configuration, choice of supportive guidewire, and proper delivery and activation of debulking devices and stents are important steps toward achieving adequate results. Excimer laser angioplasty is a debulking technology for removal of atherosclerotic plaque and associated thrombi. To date, application of laser angioplasty in anomalous coronary arteries is unreported. We herein present clinical data and discuss technical aspects related to performance of excimer laser angioplasty in three symptomatic patients with acute coronary syndrome, two having an anomalous right coronary artery and one with an anomalous circumflex artery. The delivery of laser energy in these cases resulted in rapid thrombolysis of an occlusive thrombus, successful debulking of the underlying atherosclerotic plaque, facilitation of adjunct balloon angioplasty and stenting, and ultimately, improved clinical condition.     

Excimer laser coronary angioplasty: experience with a prototype multifibre catheter in patients with stable angina pectoris.

Percutaneous excimer laser coronary angioplasty (ELCA) was performed in a first group of 20 patients with stable angina pectoris caused by significant coronary stenosis, and long-term follow-up was evaluated. Prototype 4 to 5.5 French multifibre catheters with 18-20 quartz fibres of 100 microns diameter, concentrically arranged around a central lumen for taking up a guide wire, were coupled to a commercial XeCl excimer laser. Energy was delivered at a wavelength of 308 nm with a pulse duration of 60 or 120 ns. Operating at a repetition rate of 20 Hz, mean energy transmission was 13.4 +/- 6.8 mJ per pulse. In all but one patient the lesion could be passed by the catheter. Percent diameter stenosis decreased from 77.1 +/- 10.8% to 53.1 +/- 11.8% after ELCA. Complications were frequently observed, intracoronary thrombus formation in eight instances, dissection in six patients and spasm in five cases, causing total vessel occlusion in five procedures. All complications could be managed efficaciously by thrombolytic and vasodilating drugs and/or balloon angioplasty. Subsequent PTCA was performed in case of complication or insufficient stenosis reduction after ELCA in 18 patients with adequate results (residual stenosis, 28.5 +/- 10.2%). Long-term follow-up angiography, which could be performed in 16 of 19 laser treatments, demonstrated significant restenosis in only three patients. Our preliminary results suggest that, using ELCA, ablation of atherosclerotic lesions is feasible in most cases. However, compared with PTCA, stenosis reduction is significantly less, and the acute complication rate is much higher. Thus, further improvements of the catheter system are necessary in order to realize the advantages of excimer laser ablation, which can be demonstrated by experimental studies.     

Validation of a three-dimensional intravascular ultrasound imaging technique to assess atherosclerotic burden: potential for improved assessment of cardiac allograft coronary artery disease

BACKGROUND: Serial analysis of intracoronary ultrasound images is limited by difficulty with spatial registration and inability to assess the full extent of vascular disease. Three-dimensional (3D) imaging of coronary arteries can potentially overcome these limitations. OBJECTIVES: To assess the feasibility of using a PC-based 3D rendering technique to assess atherosclerotic burden. METHODS: To define the accuracy of 3D intravascular ultrasound (IVUS) measurements in vitro, six porcine iliac arteries and nine human cadaveric iliac arteries were pressure fixed and imaged with a commercial IVUS system. 3D datasets of the arteries were constructed, and measurements were correlated with histomorphometry. In vivo studies of 53 arterial segments (19 right coronary, 26 anterior descending and eight circumflex) were scanned in 18 patients, one month to nine years post-transplantation and correlated to corresponding angiographic images for the presence of atherosclerosis. RESULTS: Porcine artery length and volume measurements by IVUS showed a high degree of correlation with histomorphometry measurements (r=0.99, P<0.0003 and r=0.99, P<0.0001, respectively). Human arterial length, total artery volume and lumen volume measurements were similarly correlated (r=0.99, P<0.0001, r=0.99, P<0.0001 and r=0.98, P<0.0001, respectively). For plaque volume, r=0.84, P<0.05. In vivo 3D IVUS scans demonstrated atherosclerotic lesions in nine of 18 patients, compared with five detected by angiography alone. CONCLUSIONS: 3D IVUS imaging allows rapid and accurate measurement of arterial length, volume and plaque dimensions in addition to lumenal area and can demonstrate the full extent of atherosclerotic pathology. Because of its superior reproducibility, this technique may be used to assess the progression of coronary artery disease and allow for more accurate evaluation of interventions aimed at preventing or retarding coronary artery disease.